BAHAN KAJIAN
MK. DIT dan MAES
KEMASAMAN TANAH
DAN
PENGAPURAN
Soemarno – Maret 2012
EMPAT
KOMPONEN
TANAH
Padatan An-organik:
Mineral & Bukan
mineral
Padatan Organik :
Bahan Organik Tanah
(Senyawa organik mati)
Organisme hidup
Udara tanah …… Aerasi Tanah
Air tanah = Larutan tanah
Soil Solution, Elektrolit tanah
Sifat fisiologik penting dari
Larutan tanah adalah
“REAKSINYA” (pH) …….
Kemasaman / kebasaan
tanah
Apa itu pH Tanah?
pH adalah kemasaman atau kebasaan relatif suatu
bahan. Skala pH mencakup dari nilai 0 (nol) hingga
14.
Nilai pH 7 dikatakan netral, di bawah nilai 7 dikatakan
asam, sedangkan di atas 7 dikatakan basa.
Asam menurut teori Bronsted dan Lewry adalah
suatu bahan yang cenderung untuk memberi proton
(H+) ke beberapa senyawa lain, demikian sebaliknya
apabila basa adalah suatu bahan yang cenderung
untuk menerimanya.
Teori asam basa ini sangat baik untuk diterapkan
dimedia cair termasuk larutan tanah.
Teori asam basa lain yang sangat baik diterapkan
dalam tanah adalah Arrhenius, yaitu asam adalah
suatu bahan yang menghasilkan H+ atau
menurunkan pH apabila terdisasosiasi dalam air,
sebaliknya apabila basa dalam disosiasinya akan
menghasilkan OH- atau menaikkan pH.
KEMASAMAN (pH) tanah
Kemasaman di dalam tanah dapat dihitung
berdasarkan kedudukan ion H+.
Apabila yang diukur adalah ion H+ yang ada
dilarutan tanah (sebelah kanan, bebas)
dikatakan sebagai kemasaman aktual.
Apabila ion H+ yang diukur terdapat di
komplek jerapan tanah (sebelah kiri, tidak
bebas) dikatakan sebagai kemasaman
potensial, yang nilainya jauh lebih besar
dari kemasaman aktual.
Sedangkan apabila kedua kemasaman
tersebut dijumlahkan disebut kemasaman
total.
KEMASAMAN (pH) tanah
Kemasaman pH tanah secara sederhana
merupakan ukuran aktivitas H+ dan
dinyatakan sebagai -log10[H+].
Secara praktikal ukuran logaritma aktivitas
atau konsentrasi H+ ini berarti setiap
perubahan satu unit pH tanah berarti terjadi
perubahan 10 kali dari jumlah kemasaman
atau kebasaan.
Pada tanah yang mempunyai pH 6.0 berarti
tanah tersebut mempunyai H+ aktif
sebanyak 10 kali dibandingkan dengan
tanah yang mempunyai pH 7.0
KEMASAMAN (pH) tanah
Sebagian besar tanah tanah produktif, mulai
dari hutan humid dan sub humid hingga
padang rumput di semiarid, mempunyai pH
bervariasi antara 4.0 hingga 8.0.
Nilai di atas atau di bawah variasi tersebut
disebabkan oleh garam Ca dan Na atau ion
H+ dan Al+3 dalam larutan tanah.
Pengaruh utama pH di dalam tanah adalah
pada ketersediaan dan sifat meracun unsur
seperti Fe, Al, Mn, B, Cu, Cd dll terhadap
tanaman atau mikroorganisme.
pH =
- log [H+]
[H+] dlm larutan tanah ……….
Kemasaman aktif
[H+] dijerap koloid tanah ……….
Kemasaman potensial
Total keduanya …………………..
Kemasaman total
Misel -H
[H+]
Ion H+ terjerap, Hdd
Ion H+ terlarut
Kisaran Nilai pH tanah: 0 14
pH = 7.0 : Tanah Netral
pH < 7.0 : Tanah Masam
pH > 7.0 : Tanah basa/
Alkalin/Alkalis
Biasanya:
Tanah masam : di daerah
iklim basah
Tanah alkalis: di daerah
kering
SUMBER
KEMASAM
AN TANAH
Hdd
H+
Kation aluminium:
MISEL Al
Bahan Organik Tanah:
Al 3+
Al 3+ + H2O
Al(OH)2+ + H+
Al 3+ + OH-
Al(OH)2+
Al(OH)2+ + OH-
Al(OH)2 +
Al(OH)2+ + H2O
Al(OH)2 + + H+
Al(OH)2+ + H2O
Al(OH)3 + H+
pH &
Ketersedia
an Hara
Ca dan Mg:
Ketersediaan maksimum: pH = 6 - 8.5
Ketersediaan minim pada tanah dg : pH
< 4.0
N, K dan S:
Ketersediaan maksimum: pH > 6
Ketersediaan minim pada tanah dg : pH
< 4.0
Fosfat :
Ketersediaan maksimum: pH = 6 - 7.5
Ketersediaan minim pada tanah dg : pH <
4.0
Fe, Mn,Zn, Cu,Co :
Ketersediaan maksimum: pH < 5.5
Ketersediaan minim pada tanah dg : pH >
7.5
Mo: Ketersediaan maksimum pd
pH > 6.5
Bakteri & Aktinomisetes :
Ketersediaan maksimum: pH > 5.5
Ketersediaan minim pada tanah
dg : pH < 4.0
Problem
Kemasam
an Tanah
Kesuburan tanah
Ketersediaan Unsur
Hara
Suasana fisiologis larutan tanah tidak
sesuai bagi proses-proses
pertumbuhan akar tanaman
Keracunan unsur hara mikro
Gangguan akibat tingginya
ketersediaan/kelarutan kation
aluminium
Gangguan kehidupan jasad
renik tanah
Menurunkan kemasaman tanah =
Menaikkan pH tanah = …………..
Pengapuran
Aldd dan % KEJENUHAN Al
1. Sumber kemasaman tanah : H+, Hdd, Aldd,
2. Aldd diendapkan pada pH > 5.5 - 6.0
3. % kejenuhan Al dari KTK efektif menjadi
ukuran kemasaman tanah
4. Kejenuhan basa (KB) = jumlah basa dibagi
KTK
5. Aldd ditentukan dengan jalan ekstraksi
tanah dg 1 N KCl, dan mentitrasi
ekstraksnya dengn larutan basa
6.
HUBUNGAN pH dan KEJENUHAN
Al
pH tanah
5.4
Sumber: Abruna et al. 1975
Ultisols & Oxisols
5.1
4.8
4.5
4.2
3.9
10
20
30
40
50
% kejenuhan Al
60
70
HUBUNGAN KEJENUHAN Al dan
HASIL BEANS
% hasil maks.
100
Sumber: Abruna et
al. 1975
Ultisols & Oxisols
80
60
r =
0.93**
40
20
0
10
20
30
40
50
% kejenuhan Al
60
70
1. Konsentrasi Al dlm larutan tanah > 1
ppm menyebabkan penurunan hasil
tanaman
2. Tembakau dan kentang sangat peka thd
Al+++ dlm tanah, terutama
akarnya.
Gejalanya akar menjadi tebal, kaku dan
becak-becak jaringan mati
3. Pertumbuhan
akar
jagung
mulai
terganggu pada kondisi 60% kejenuhan
Al.
4. Al cenderung terakumulasi dalam akar
dan menghambat penyerapan dan
translokasi Ca dan fosfat menuju tajuk,
sehingga mendorong defisiensi Ca dan P.
1. Gangguan pertumbuhan tanaman pd
tanah masam dapat juga disebabkan oleh
defisiensi Ca dan/atau Mg
2. Gangguan akar tembakau pd Ultisol yg
tidak dikapur disebabkan oleh keracunan
Al dan defisiensi Ca.
3. Kalau Al diendapkan (dg menggunakan
MgCO3) dan tidak ditambahkan Ca,
pertumbuhan akar tembakau akan
berhenti dalam waktu 60 jam.
4. Tanah masam di daerah tropis defisien Ca
tanpa menunjukkan masalah toksisitas Al.
5. Misalnya Tanah masam di Hawaii, pH <
5.0, namun Aldd nya sedikit; pengapuran
berfungsi seperti pemupukan Ca
6. Tanah masam di Brazil sangat miskin Mg
dan respon positif thd pupuk Mg.
TOKSISITAS Al & DEFISIENSI Ca thd
AKAR TEMBAKAU
% maks.
pemanjangan akar
Dikapur CaCO3, pH 5.8, 4.4
meq Ca++
100
80
Dikapur MgCO3,
pH 5.6, 0.4 meq
Ca++
60
40
Tdk Dikapur,
pH 4.2,
0.4 meq Ca++
20
0
1
2
waktu (hari)
Sumber: Abruna et al. 1975
Ultisols & Oxisols
3
EFEK Al thd PERTUMBUHAN
AKAR
Tanah
pH
Aldd % Kejenuhan
Berat kering akar tanaman:
me/100 g Al
Jagung (mg/pot)
Sorghum
Ultisol
4.8
4.5
3.9
4
6
11
40
57
87
931
874
209
400
296
19
Oxisol
4.8
4.5
4.0
3
4
5
52
70
87
687
630
389
345
126
128
Sumber: Brenes & Pearson, 1973.
MENGUKUR KEMASAMAN (pH)
tanah
Ada 2 metode yang paling umum digunakan untuk
pengukuran pH tanah yaitu kertas lakmus dan pH
meter. Kertas lakmus sering di gunakan di lapangan
untuk mempercepat pengukuran pH.
Penggunaan metode ini di perlukan keahlian
pengalaman untuk menghindari kesalahan.
Lebih akurat dan secara luas di gunakan adalah
penggunaan pH meter, yang sangat banyak di
gunakan di laboratorium. Walaupun pH tanah
merupakan indikator tunggal yang sangat baik
untuk kemasaman tanah, tetapi nilai pH tidak bisa
menunjukkan berapa kebutuhan kapur.
Kebutuhan kapur merupakan jumlah kapur
pertanian yang dibutuhkan untuk mempertahankan
variasi pH yang di inginkan untuk sistem pertanian
yang digunakan.
Kebutuhan kapur tanah tidak hanya berhubungan
dengan pH tanah saja, tetapi juga berhubungan
dengan kemampuan menyangga tanah atau
kapasitas tukar kation (KTK).
PENGELOLAAN KEMASAMAN (pH)
tanah
Tanah masam adalah tanah ber-pH rendah
(pH di bawah 6), semakin rendah pH
tanahnya maka semakin ekstrim
kemasamannya.
Kendala Tanah Masam
1. Unsur hara makro (terutama
N,P,K,Ca,Mg) tidak tersedia dalam
jumlah cukup, efektifitas dan efisiensi
pemupukan makro (urea, TSP, KCl)
juga rendah.
2. Beberapa unsur (terutama Al dan Fe)
tersedia berlebih sehingga sering
meracun pada tanaman.
3. Menghambat perkembangan
mikroorganisme tanah.
PENGELOLAAN KEMASAMAN (pH)
tanah
Pengapuran untuk Meningkatkan pH Tanah
Perbaikan pH tanah bisa diakatakan menyelesaikan
50% masalah kesuburan tanah. Salah satu cara
meningkatkan pH tanah dengan pengapuran
menggunakan kapur pertanian (kaptan) atau dolomit.
Beberapa hal yang perlu diperhatikan :
1.
2.
3.
4.
5.
Idealnya paling lambat pengapuran dilakukan 2 minggu
sebelum tanam, karena bahan kapur termasuk bahan
yang lambat bereaksi dengan tanah.
Setelah pengapuran sebaiknya tanah dicangkul
(dibajak) agar kapur bisa merata masuk dekat zona
perakaran.
Pengairan setelah pengapuran sangat diperlukan.
Peningkatan pH tidak bisa terjadi seketika, melainkan
pelan dan bertahap.
Dosis kapur disesuaikan pH tanahnya, tetapi sebagai
pedoman praktis dosis berkisar 500 kg/Ha 2 ton/Ha.
Catatan :
Dolomit juga harus secara rutin digunakan pada tanah pH
normal, karena unsur Ca dan Mg pada dolomit sangat
dibutuhkan tanaman.
PENGELOLAAN KEMASAMAN (pH)
tanah
Kapur pertanian merupakan mineral yang
berasal dari alam yang merupakan sumber
hara kalsium. Kaptan yang mempunyai
reaksi basa dapat menaikkan pH tanah.
Kaptan yang banyak digunakan dalam
pertanian adalah kalsit (CaCO3)
Manfaat : Untuk menetralkan pH tanah pada
tanaman sayuran⁄hortikultura dll . Untuk
menanggulangi beberapa jenis jamur ⁄bakteri
pada tanah. Untuk menetralkan tanah
gambut sehingga menambah tingkat
kesuburan tanah dll
Spesifikasi :
Kadar CaCO3 + MgCO3 93.3 % , Kadar CaO
+ MgO 58.8 %, Kadar Air Saat dikemas 1.00
%, Mesh 40 – 100, Berat bersih kemasan 50
kg
KAPTAN
Kapur Pertanian (Kaptan) memiliki kandungan kalsium
dan magnesium yang tinggi, ukiran butiran (mesh) yang
halus dan sesuai dengan standar yang telah ditetapkan
oleh SNI (Standar Nasional Indonesia)
KAPTAN dapat diproduksi dengan menggunakan mesin
crusher dan milling yang mampu memproduksi kaptan
sekitar 1.500 ton per bulan.
Spesifikasi Kaptan
Kadar CaCO3 + MgCO3 : 91.53%
Kadar CaO + MgO : 50.23%
Kadar air saat dikemas : 1.00%
Mesh 40 – 100 : 82.01%
Berat bersih perkemasan 50 Kg
Kapur Pertanian merupakan mineral yang berasal dari
alam yang merupakan sumber hara kalsium. Kaptan
yang mempunyai reaksi basa dapat menaikkan PH
tanah. Kaptan yang umum banyak digunakan dalam
pertanian adalah Kalsit (CaCo3)
KAPTAN
Dosis Kaptan
1. Sebelum melakukan pengapuran, sebaiknya terlebih
dahulu dilakukan pemeriksaan PH tanah dengan
menggunakan kertas lakumus atau PH soil tester, dapat
meminta bantuan penyuluh terdekat dari dinas pertanian/
perkebunan/ perikanan
2. Pengapuran dengan dosis tersebut untuk jangka
panjang atau 3 tahunan keatas, baru dilakukan
pengapuran ulang. Ada anjuran para ahli sebaiknya
dilakukan penambahan KAPTAN sebanyak 10% – 20% dari
dosis diatas pada setiap 6 bulan sekali atau bersamaan
dengan waktu pemupukan dilakukan
3. Untuk tanah marginal, umumnya berwarna terang atau
pada tanah podsolik merah dan kuning atau pada tanah
yang miskin kandungan bahan organik, dianjurkan
pemberian kompos, bokasi atau pupuk organik
4. Mutu KAPTAN yang tepat selain kandungan kalsium
(CaCO) yag tinggi kisaran 42% sampai 51%, tingkat
kehalusan dan kelembutan (mesh) yang terbaik adalah 60
sampai 100 mesh
5. KAPTAN berkualitas tinggi bereaksi lebih cepat dan
sempurna, sedangkan KAPTAN berkualitas renddah
memerlukan waktu sangat lama untuk dapat merubah PH
tanah, bahkan bisa sampai tahunan. Adapun KAPTAN
yang memenuhi standar, dapat langsung bermanfaat
dengan cara pemberian yang tepat
KALSIUM KARBONAT
Kalsium karbonat adalah bahan aktif dalam kapur
pertanian, dan biasanya merupakan penyebab utama
air keras. Hal ini biasanya digunakan secara medis
sebagai kalsium suplemen atau sebagai antisida, namun
konsumsi yang berlebihan dapat membahayakan
Kalsium karbonat memunyai beberapa sifat khas
khususnya :
1. Bereaksi dengan asam yang kuat, dan melepaskan
karbon dioksida CaCO3(s) + 2HC1(aq) ---- CaC12(aq)
+ CO2(g) + H2O(1)
2. Ia melepaskan karbondioksida pada pemanasan
(diatas 840 C dalam kasus CaCO3), untuk membentuk
kalisum oksida, yang biasa disebut kapur, dengan reaksi
178 KJ/ Mol
CaCO3 ---------------- CaO + CO2
KALSIUM KARBONAT
Kalsium karbonat akan bereaksi dengan air yang
penuh dengan karbon dioksida untuk membentuk
larut kalsium bikarbonat
CaCO3 + CO2 + H2O ? Ca(HCO3)2
Reaksi ini penting dalam erosi dari batuan
karbonat, membentuk gua gua, dan menyebabkan
air keras di berbagai daerah
Sebagian besar dari kalsium karbonat yang
digunakan dalam industri diekstraksi dengan
pertambangan atau penggalian. Kalsium karbonat
murni (misalnya untuk keperluan makanan atau
farmasi), dapat dihasilkan dari sumber yang digali
murni (biasanya marmer) atau kalisum karbonat
disusun oleh kalsinasi mentah oksida kalsium. Air
ditambahkan untuk memberikan kalsium
hidroksida, dan karbon dioksida dilewatkan untuk
mengendapkan kalsium karbonat yang diinginkan,
sebagaimana dimaksud dalam industri sebagai
endapan kalsium karbonat
KALSIUM KARBONAT
Karbonat sering ditemukan dalam pengaturan
geologi, kalsium karbonat terjadi sebagai polimor
aragonit dan kalsit.
Polimorf adalah mineral dengan rumus kimia yang
sama tetapi struktur kimia yang berbeda.
Mineral karbonat membentuk jenis batu : kapur,
marmer, travertine, tufa, dan lain lain.
Kalsit umumnya terjadi sebagai sedimen dalam
pengaturan laut. Kalsit biasanya ditemukan di
sekitar lingkungan tropis yang hangat. Endapan
kalsit di lingkungan dangkal hangat lebih dari itu
tidak dalam lingkungan yang lebih dingin karena
lingkungan lebih hangat tidak mendukung
pembubaran CO2.
Hal ini dianalogikan dengan CO2 yang larut dalam
soda. Ketika anda mengambil tutup botol soda,
CO2 bergegas keluar. Sebagai soda menghangat,
& karbon dioksida dilepaskan.
Prinsip yang sama dapat diterapkan pada kalsit di
laut
SUPER DOLOMITE
Super Dolomite adalah pupuk magnesium
berkadar tinggi, digunakan baik untuk tanah
pertanian, tanah perkebunan, kebutuhan industri
dan bahkan untuk perikanan /tambak.
Bahan baku Super Dolomit berasal dari batuan
dolomit yang ditambang dari kawasan
pertambangan di Gresik.
Menurut pusat Penelitian dan Pengembangan
Geologi Direktorat Jenderal Pertambangan Umum
Bandung, batuan dolomit di Gresik adalah jenis
batuan dolomit yang berkualitas tinggi, yakni
dengan kadar MgO 18% - 21%
Keunggulan Pupuk Super Dolomit
1. Ukuran butir seragam, dan minimal 95% lolos
ayakan 100 mesh
Kadar MgO minimal 18%
Daya larut dalam air cepat, sehingga cepat
tersedia bagi tanaman
Sebagai pupuk Mg memiliki efektifitas tinggi
Daya tangkal pengasaman cepat
Untuk mencapai produktifitas yang sama hanya
memerlukan 60% super dolomit bila dibandingkan
dengan dolomit biasa, sehingga mengurangi biaya
aplikasi pemupukan dan biaya pengiriman
2. Pemakaian Kieserite dapat digantikan oleh
super dolomit, jika super dolomit telah dicampur
dengan ZA.
Selain itu dapat memberikan manfaat lebih tinggi
sebagai berikut :
Pemakaian kombinasi super dolomit + ZA mampu
memasok hara Magnesium (Mg) dan Sulfat
Nitrogen pada tanaman dan tidak mengasamkan
tanah
Penghematan biaya produksi karena pemakaian
Super Dolomit + ZA harganya lebih murah
dibandingkan dengan Kieserite
Penghematan devisa, karena import Kieserite
dapat ditiadakan.
Kegunaan Super Dolomite
1. Penyembuhan
Untuk tanaman, kekurangan Magnesium (Mg)
berakibat sangat fatal. Tanaman yang menderita
kekurangan Magnesium ditandai dengan daun yang
menguning, sehingga kehilangan kemampuan
menghasilkan CO2, dengan demikian, pemberian
pupuk Super Dolomite akan mampu menambah
unsur hara Magnesium yang diperlukan tanaman,
sehingga warna daunnya menjadi hijau lagi
2. Amelioran
Pada tanah masam atau PH rendah, selain
pertumbuhan tanaman akan terganggu, juga
keracunan A1 dan Fe sering terjadi. Dengan
pemberian Super Dolomit, selain dapat menetralisir
A1 dan Fe, juga menaikkan PH tanah sehingga
penyerapan unsur unsur hara, N Fosfor (P), K oleh
tanaman menjadi baik
3. Pembenah
Pemberian pupuk berbentuk Amonium (UREA/DAP)
dan kalcium (KCl) yang terlalu banyak, dapat
mengakibatkan kekurangan Magnesium (Mg). Selain
itu pupuk nitrogen mempunyai kecenderungan
menciptakan suasana masam. Pemberian pupuk
Super Dolomit mampu menetralisir reaksi tanah yang
bersifat masam akibat pemberian pupuk yang
berlebihan
CARA PENGGUNAAN SUPER DOLOMITE
1. Disebar/ Dicampur merata
Cara ini dilakukan apabila pupuk super dolomit
digunakan untuk memperbaiki tanah yang buruk.
Pupuk ini disebar/ dicampur merata diatas tanah pada
waktu tanah terakhir yang bisanya dilakukan sebelum
tanaman ditanam atau benih ditabur
2. Dimasukkan pada lubang tanaman
Bila sebagai pupuk dasar pada tanaman perkebunan,
Super Dolomit ditempatkan pada dasar lubang
tanaman, kemudian diaduk merata dengan pupuk dan
tanah pada dasar lubang, setelah itu ditimbun sedikit
dengan tanah, baru diatas timbunan ditempatkan bibit
tanaman
3. Super Dolomit dicampur dengan ZA / Pupuk lainnya
Bila super dolomit diperlukan dalam pencampuran
pupuk maka cara pemberiannya dilakukan dengan
cara sebar merata dalam larikan sejajar baris tanaman,
sekeliling batang tanaman atau ditempatkan pada
lubang yang dibuat dikanan – kiri tanaman
Untuk meniadakan reaksi tanah masam, Pupuk Super
Dolomit dicampurkan pada waktu pengolahan tanah
secara merata dan dilakukan 2 minggu sebelum
tanam.
BENTUK BAHAN KAPUR
Kapor Oksida: Kapur Sirih
Kemurniannya: 85 - 95%
Pembuatannya:
CaCO3 + panas
CaMg(CO3)2 + panas
CaO + CO2
CaO +MgO + CO2
Reaksinya dlm tanah:
MISEL - H + CaO
MISEL - Ca + H2O
CaO + H2O
Ca(OH)2 + 2 H2CO3
Ca(OH)2
Ca(HCO3)2 + 2 H2O
% Oksida CaO
Ekuivalen oksida Ca
Daya netralisasi
Persentase unsur Ca
: 77%
: 102
: 182.1 (kesetaraan CaCO3)
: 55
% Oksida MgO
Persentase unsur Mg
: 18%
: 10.8
BENTUK BAHAN KAPUR
Kapor Hidroksida: Kapur Tembok
Kemurniannya: 95 - 96%
Pembuatannya:
CaO + MgO + H2O
Ca(OH)2 + Mg(OH)2
Reaksinya di udara lembab terbuka:
Ca(OH)2 + CO2
CaCO3 + H2O
Mg(OH)2 + CO2
NgCO3 + H2O
Reaksinya dlm tanah:
MISEL - H + Ca(OH)2
MISEL - Ca + 2H2O
Ca(OH)2 + 2 H2CO3
Ca(HCO3)2 + 2 H2O
% Oksida CaO
Ekuivalen oksida Ca
Daya netralisasi
Persentase unsur Ca
: 60%
: 76.7
: 136.9 (kesetaraan CaCO3)
: 42.8
% Oksida MgO
Persentase unsur Mg
: 12%
: 7.2
BENTUK
BAHAN
KAPUR
Kapor Karbonat : Kapur Kalsit
= CaCO3
Kapur Dolomitik = CaMg(CO3)2
Dolomit
= MgCO3
Kemurniannya : 75 - 99%
Pembuatannya:
Batuan CaCO3 digiling
Kapur giling
Reaksinya dlm tanah:
MISEL - H + CaCO3
MISEL - Ca + H2O
+ CO2
Oksida CaO = 44.8%; MgO = 6.70%
Ekuivalen oksida Ca
: 54.10
Daya netralisasi
: 96.6 (kesetaraan CaCO3)
Persentase unsur Ca = 32; Mg = 4.03
Karbonat:
CaCO3 = 80%; MgCO3 = 14%
Total = 94%
PENGARUH
KAPUR PADA
TANAH
Pengaruh Fisik:
- Membantu granulasi agregasi
- Memperbaiki struktur
tanah
- Tata Udara (Aerasi)
- Tata Air / Pergerakan
air
Pengaruh Kimia:
(Bila tanah dg pH= 5.0 dikapur hingga ph naik
menajdi 6.0)
- Kepekatan kation hidrohen menurun
- Kepekatan anion hidroksil meningkat/ naik
- Daya larut Fe, Mn dan Al akan menurun
- Ketersediaan fosfat dan Mo akan diperbaiki
- Cadd dan Mgdd akan naik
- Persentase kejenuhan basa (KB) akan naik
- Ketersediaan kalium berubah tgt keadaan.
Pengaruh Biologik:
1. Merangsang kegiatan jasad tanah, termasuk
mikroba tanah
2. Membantu pembentukan humus
3. Aminisasi, amonifikasi, oksidasi belerang dipercepat
4. Fiksasi nitrogen dari udara secara biologis
dirangsang
5. Nitrifikasi dipercepat
JENIS TANAMAN yg SESUAI TANAH
MASAM dg KEBUTUHAN KAPUR
MINIMUM
Kebutuhan
yg toleran
kapur
(t/ha)
Kejenuhan
pH
Varietas tnm
Al
(%)
0.25 - 0.5
68 - 75
ubikayu, mangga, mente
4.5 - 4.7
Gogo,
Jeruk, Nanas,
Desmodium, Centrosema,
Paspalum
0.5 - 1.0
Plantain
1.0 - 2.0
bean
45 - 58
4.7 - 5.0
Cowpea,
31 - 45
5.0-5.3
Jagung, Black
Sumber: Spain et al. 1975
MEKANISME TOLERANSI /
KEPEKAAN TANAMAN thd Al dlm
TANAH
1. Morfologi akar.
Varietas yg toleran Al mampu
menumbuhkan dan tidak mengalami
kerusakan ujung-ujung akar pd kondisi
tanah masam kaya Al
2. Perubahan pH rhizosfer.
Varietas yg toleran Al mampu menaikkan
pH zone rhizosfernya, sdg varietas yg peka
menurunkan pH tsb. Perubahan pH ini
diduga akibat dari penyerapan anion
diferensial-selektif, sekresi asam organik,
CO2 dan HCO3-.
3. Lambatnya translokasi Al ke tajuk.
Varietas yg toleran Al mengakumulasikan
Al dlm akar, dan mentranslokasikan ke
tajuk secara lebih lambat dp jenis yg peka.
MEKANISME TOLERANSI /
KEPEKAAN TANAMAN thd Al dlm
TANAH
4.
Al dalam akar tidak menghambat
penyerapan dan translokasi Ca, Mg dan K
dlm varietas yg toleran Al.
5.
Toleransi varietas kedelai thd Al
berhubungan dengan penyerapan dan
translokasi Ca.
6. Toleransi varietas keNTANG
thd Al
berhubungan dengan translokasi Mg dan
K.
7. Toleransi varietas padi
thd Al
berhubungan dengan tingginya kandungan
Si dlm tanaman.
8. Varietas yg toleran Al tidak mengalami
hambatan penyerapan dan translokasi
fosfat; tdk dmk varietas yg peka.
1.
Tujuan utama pengapuran adalah
menetralisir Aldd, dan biasanya diikuti oleh
kenaikan pH hingga 5.5.
2. Kalau diduga ada keracunan Mn, maka
pH dinaikkan 6.0
3. Faktor-faktor yg harus diperhatikan:
1. Jml bahan kapur yg diperlukan untuk
menetralkan
Aldd hingga tingkat yg sesuai bagi
tanaman
2. Kualitas bahan kapur
3. Cara penempatan / aplikasi bahan
kapur ke tanah.
RESPON
TANAMAN
thd
PENGAPUR
AN
Umumnya pertumbuhan tanaman
menjadi lebih baik.
Tnm kacang-kacangan menyukai
kapur, termasuk kedelai dan
kacang tanah
Alasan terjadinya respon tanaman:
1. Pengaruh langsung unsur hara Ca dan Mg
2. Dinetralkannya senyawa-senyawa toksik
3. Penekanan gangguan penyakit tanaman
4. Ketersediaan beberapa unsur hara meningkat
5. Rangsangan kegiatan jasad mikro akan
meningkatkan ketersediaan hara
6. Beberapa tanaman tertentu tidak senang
pengapuran, misalnya semangka.
7. ……. Dll.
1. Kamprath (1970):
Dosis kapur = 1.5 x ( me Aldd topsoil)
= m.e. Ca yg harus diaplikasikan sbg
kapur
2.
3.
4.
5.
6.
7.
Dosis kapur yg dihitung dg cara ini mampu
menetralkan 85 - 90 % Aldd dlm tanah yg
mengandung 2 - 7% bahan organik
Faktor 1.5 digunakan untuk menetralkan H+ yg
dilepaskan oleh bahan organik atau hidroksida Fe
dan Al kalau pH tanah meningkat
Dalam tanah yg kaya bahan organik, faktor
tersebut menjadi 2.0 atau 3.0, karena adanya Hdd.
Untuk setiap satu m.eq. Aldd dlm tanah diperlukan
aplikasi 1.5 meq Ca atau setara dg 1.65 ton CaCO3
per ha.
Faktor penting lain adalah kandungan Aldd dlm
tanah yang dapat ditolerir oleh tanaman tertentu
Jagung sensitif terhadap kejenuhan Al 40-60%.
Pengapuran hingga kejenuhan Al = 0% dapat
menguntungkan, namun pengapuran untuk
menurunkan kejenuhan Al menjadi 20% dapat
lebih ekonomis.
RESPON HASIL TERHADAP
PENGAPURAN
% Hasil maks.
100
Rumput
gajah
80
60
40
Jagung
Sorghum
20
00
10
20
30
40 50 60
% kejenuhan Al
70
Sumber: Abruna et al. 1975
Oxisols & Ultisols
80 90 100
1. Kapur biasanya dibenamkan sedalam 15 cm
beberapa hari sebelum tanam.
2. Tanah Oksisol sangat masam yg topsoilnya telah
dikapur hingga pH 5.5 , sebagian besar akar
jagung tumbuh dalam topsoil. Tingginya
kandungan Aldd
dalam subsoil mencegah
pertumbuhan akar lebih dalam.
3. Penempatan kapur pada lapisan tanah yg lebih
dalam mengakibatkan perakaran tanaman tumbuh
lebih dalam dan hasil tanaman lebih baik
4. Deep placement kapur dimungkinkan pada tanahtanah berpasir yang strukturnya baik.
5.
PENGAPURAN & HASIL JAGUNG
Hasil biji , t/ha
6
Zone pengapuran 030 cm
5
4
3
2
1
1
Zone
pengapuran 015 cm
2
Sumber: Gonzales,
1973
Tanah Oxisols
3
4
5
6
Dosis kapur ( ton/ha)
7
1. Efek residu pengapuran tergantung pada
seberapa cepat Ca dan Mg digantukan
oleh residu kemasaman dari pupuk
nitrogen.
2. Pada tanah Hydrandept
Selama lima tahun sejak aplikasi 2 ton
kapur/ha ternyata nilai Aldd dalam tanah
dipertahankan sekitar 1 meq, semula
sebesar 3 m.eq, meskipun sebagian besar
Ca++ telah tercuci. Setelah lima tahun
efek residu pengapuran lenyap.
3. Pada Oxisol berpasir.
Jagung dan kedelai respon positif
terhadap kapur
enam tahun setelah
aplikasi, respon hasil meningkat dg
waktu, diduga karena pelarutan partikel
kasar kapur.
KELEBIHA
N
Pemberian
KAPUR
Kelebihan: penambahan kapur yg
mengakibatkan meningkatan pH
tanah melebihi yang diperlukan
untuk
pertumbuhan
optimum
tanaman.
Tanaman akan menderita, terutama
pada tahun pertama aplikasi kapur
Biasanya terjadi pada tanah berpasir /
berdebu yg miskin bahan organik
Pengaruh
buruk
pengapuran
yg
berlebihan:
1. Kekurangan Fe, Mn, Cu dan Zn
2. Ketersediaan fosfat mungkin menurun
karena
pembentukkan senyawa kompleks dan
tidak larut
3. Serapan fosfat dan penggunaannya dlm
metabolisme tanaman dapat terganggu
4. Serapan B dan penggunaannya dapat
etrganggu
5. Perubahan pH yang terlalu melonjak
dapat berpengaruh buruk
6. ………dst.
7. ……. Dll.
Apakah
KAPUR
perlu
diberikan?
Penggunaan kapur harus didasarkan
pada :
Kemasaman Tanah dan
Kebutuhan Tanaman
1. Sebelum mengapur tanah, karakteristik
kimia tanah perlu diteliti
2. pH tanah dan Kejenuhan Basa harus
ditentukan secara akurat : Lapisan atas
dan Lapisan bawah
3. Cara lain adalah menentukan Aldd
4. ……….
1. Kebutuhan kapur untuk tanaman secara
umum atau untuk tanaman tertentu
2. Pengelompokkan respon tanaman thd
kapur :
- Tanaman Senang Pengapuran
Tanaman
tidak
senang
Pengapuran
- Tanaman netral
Bentuk
KAPUR yg
dipakai
Lima faktor unt menentukan bentuk
kapur :
1. Jaminan mutu kimia bahan kapur
2. Harga bahan
3. Kecepatan reaksi dengan tanah
4. Kehalusan bahan kapur
5.
Hal
lain-lain
(penyimpangan,
pembungkusan dsb.
Kecepatan Reaksi:
1. Kapur kaustik (kapur tohor dan tembok)
lebih cepat bereaksi dg tanah dp kapur giling
2. Kapur dolomitik bereaksi lebih lambat dp
kapur kalsitik
3. Bentuk tepung halus lebih cepat bereaksi dg
tanah
4. …. Dll.
Pertimbangan biaya:
1. Harga bahan kapur
2. Biaya angkut ke lahan usaha
3. Biaya aplikasi bahan kapur ke lahan
usaha
4. ….. dll
Jumlah
KAPUR yg
diaplikasikan
Enam faktor penting unt menentukan
jumlah kapur :
1. Karakteristik tanah:
Lapisan atas: pH, Aldd, Tekstur &
Struktur, BOT
Lapisan bawah: pH, Aldd, Tekstur &
Struktur
2. Tanaman yg akan ditanam
3. Lamanya pergiliran tanaman
4. Macam bahan kapur dan komposisi
kimianya
5. Kehalusan bahan kapur
6. Pengalaman praktis
Karakteristik Tanah :
1. Tekstur dan BOT menentukan besarnya
kapasitas jerapan
2. Semakin tinggi Kapasitas jerapan dan Aldd,
semakin banyak kapur diperlukan
3. Kemasaman dan Aldd tanah lapisan bawah
ikut menentukan jumlah kapur
Contoh: Jml kapur giling unt tanah mineral setebal 20
cm seluas 1 ha:
Untuk menapai pH
5.2
5.5
6.0
Jumlah kapur, ton/ha
1.2 x me Aldd
1.5
2.1
Teknologi
Aplikasi
KAPUR
Cara Aplikasi :
1. Kapur disebar di permukaan tanah yg
baru dibajak, kemudian dicampur
rata dengan tanah olahan
2. Kapur disebar di permukaan tanah,
tanah dibajak (diolah) dan dicampur
rata
Waktu Aplikasi :
1. Biasanya sebelum tanam
2. Kapur diberikan bila diperkirakan tidak
turun hujan pd saat aplikasi
3. ……
1. Pertanaman tunggal
2. Pertanaman majemuk: Pola pergiliran tanaman
Kapur diberikan pd tanaman yg paling
memerlukan pengapuran
TEKNOLOGI PENGAPURAN TERPADU
Prinsip utama pengelolaan tanah masam adalah
menaikkan pH tanah dan mengurangi kejenuhan
Al yang meracun, serta meningkatkan
ketersediaan hara tanaman, terutama unsur hara
P sehingga sesuai dengan pertumbuhan tanaman
yang optimal.
Pengapuran merupakan teknologi yang paling
tepat dalam pemanfaatan tanah masam di
dasarkan atas beberapa pertimbangan:
1. Rekasi kapur sangat cepat dalam menaikkan
pH tanah dan menurunkan kelarutan Al yang
meracun.
2. Respons tanaman sangat tinggi terhadap
pemberian kapur pada tanah masam.
3. Efek sisa kapur atau manfaat kapur dapat
dinikmati selama 3 sampai 4 tahun
berikutnya.
4. Bahan kapur cukup tersedia dan relatif
murah
PENGELOLAAN KEMASAMAN (pH)
tanah
Teknologi pengapuran terpadu meliputi topikTOPIK :
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Kapur pengendali kemasaman tanah
Peranan kapur dalam meningkatkan serapan P
Penetapan kebutuhan kapur
Manfaat kapur bagi pertumbuhan dan hasil
tanaman
Pengaruh sisa pupuk P bersama kapur
Jenis kapur dan cara penggunaannya
Pengapuran harus di sertai dengan pemupukan
Peran bahan organik pada tanah masam
Integrasi kapur, bahan organik, dan pupuk
Efek kapur berlebihan
Pengapuran dan pengaturan pola tanam
Budidaya lorong "Alley cropping"
memantapkan pengapuran
Perhitungan keuntungan penggunaan kapur
PENGELOLAAN KEMASAMAN (pH)
tanah
TEKNOLOGI PENGAPURAN TERPADU:
Teknologi pengapuran yang diintegrasikan dengan
penggunaan bahan organik dan pupuk buatan yang
disertai dengan budidaya lorong dengan pola
tanam yang menguntungkan .
WHEN TO APPLY LIME AND FERTILIZER
Kenneth Wells
Department of Agronomy
When lime and fertilizers are applied to soils, many
chemical reactions take place — some immediately, and
some over long periods of time. These reactions have a
great influence on when lime and fertilizer can be applied
and how efficiently fertilizer is taken up by growing crops,
and this influences the economic returns from lime and
fertilizer use.
When applied to soil, the liming material reacts with
soil moisture to release particles of calcium or, in the case
of dolomitic lime, magnesium. The rate at which the lime
material dissolves to release these particles is largely
controlled by how finely it is ground and the chemical form
of the material (carbonate, oxide or hydroxide).
The finer the material, the more rapidly it dissolves. Oxides
(burned lime) and hydroxides (hydrated lime) are more
soluble in water and react much more quickly than
carbonate forms of lime (calcitic aglime or dolomitic
aglime).
http://www.ca.uky.edu/agc/pubs/agr/agr5/agr5.pdf….. Diunduh 27/2/2012
APLIKASI KAPUR
Timing Lime Application for Best
Results
In general, follow these guidelines to achieve the best results
with our Superfine formulation:
1.
2.
3.
4.
in a rotation, apply before the crop with the greatest acid
sensitivity
if you plan on reducing tillage, apply one year before
the most acid sensitive crop, and in a greater quantity
make sure that the root disease Take-All has been
controlled before applying lime fertiliser ahead of a
wheat or critical crop
lime fertiliser application is generally not recommended
for permanent pastures, due to issues of incorporation
GUIDE TO LIME APPLICATIONS
IGC Document 143/08/E
http://www.aglimefertilisers.com.au/applications.html….. Diunduh 27/2/2012
MENGUKUR KEMASAMAN
The term pH stands for the potential (p) of the
hydrogen ion (H+) in water. It is actually a way of
reporting the concentration of H+ in solution using an
electrical "potential" to measure H+. The pH of any
solution is one of the easiest laboratory
measurements to make using a pH meter and an
electrode specifically designed to measure hydrogen
(pH electrode). Color indicators and litmus paper are
a quick alternative for less precise measurements. By
mixing a quantity of soil with demineralized or
distilled water (usually a 1:1 mixture), we can
measure the pH of the water solution in equilibrium
with the soil.
The pH measurement is based on a scale from 1 to 14
(pH is reported as the negative logarithm of the
hydrogen ion activity). At a pH of 7.0, there is an
equal balance of hydrogen (H+) ions and hydoxyl (OH) ions, and the soil (actually the soil-water
suspension) is said to be neutral. Because the pH
measurement is logarithmic, each unit change in pH
represents a ten-fold increase in the amount of
acidity or basicity. That is, a soil solution with a pH of
6.0 has 10 times as much active H+ as one with a pH
of 7.0.
http://hubcap.clemson.edu/~blpprt/acidity2_review.html ….. Diunduh 27/2/2012
KETIDAK-SUBURAN TANAH MASAM
When the pH falls below 6.0, the availability of
nutrients such as phosphorus, potassium, calcium, and
magnesium decreases. The availability of the metallic
micronutrients, however, like zinc, manganese, copper,
and iron increases as the pH decreases.
Plants don't need aluminum to grow. It's not an
essential plant nutrient. Aluminum, however, is one of
the prominent mineral components of silt and clay.
Therefore, the earth's crust is naturally high in
aluminum. Like zinc, manganese , copper and iron, the
more acid the soil, the more aluminum will be
dissolved into the soil solution. If the pH is allowed to
drop much below 5.5, the availability of manganese
and aluminum is increased to the point that they could
become toxic to plants.
Aluminum toxicity to plants is the main concern
we have with acid soils in our region.
Charles C. Mitchell. Extension Agronomist-Soils & Professor
Auburn University
http://hubcap.clemson.edu/~blpprt/acidity2_review.html ….. Diunduh 27/2/2012
PROBLEM TANAH MASAM DAN
TANAH ALKALIS
Problems in very acid soils
Problems in alkaline soils
*Aluminum toxicity to plant
*Iron deficiency
roots
*Manganese toxicity to
*Manganese deficiency
plants
*Calcium & magnesium
*Zinc deficiencies
deficiency
*Molybdenum deficiency in
*excess salts (in some soils)
legumes
*P tied up by Fe and Al
*P tied up by Ca and Mg
*poor bacterial growth
*bacterial diseases in
potatoes
*reduced nitrogen
transformations
Charles C. Mitchell. Extension Agronomist-Soils & Professor
Auburn University
http://hubcap.clemson.edu/~blpprt/acidity2_review.html ….. Diunduh 27/2/2012
FAKTOR pH TANAH
Parent material.
Soils of the Piedmont and Sandstone Plateau regions of Alabama are very acid
because of the acid nature of the rocks (granites and sandstones, respectively)
which formed these soils. Limestone valley soils were formed from basic rocks
(limestones) but may be acid on the surface because of time and weathering.
Some Black Belt Prairie soils may be alkaline because the Selma chalk (soft
limestone) which formed the soils is alkaline.
Rainfall/leaching.
Rainfall also affects soil pH. Water passing through the soil leaches basic cations
such as calcium (Ca2+), magnesium (Mg2+), and potassium (K+) into drainage
water. These basic cations are replaced by acidic cations such as aluminum (Al3+)
and hydrogen (H+). For this reason, soils formed under high rainfall conditions
are more acid than those formed under arid conditions.
Fertilizers.
Both chemical and organic fertilizers may eventually make the soil more acid.
Hydrogen is added in the form of ammonia-based fertilizers (NH4+) , urea-based
fertilizers [CO(NH2)2], and as proteins (amino acids) in organic fertilizers.
Transformations of these sources of N into nitrate (NO3-) releases H+ to create
soil acidity. Therefore, fertilization with fertilizers containing ammonium or even
adding large quantities of organic matter to a soil will ultimately increase the soil
acidity and lower the pH.
NH4+ + 2O2 ---------------- NO3-+ 2H+ + H2O
Bacteria
Plant uptake.
Plants take up basic cations such as K+, Ca++, and Mg++. When these are removed
from the soil, they are replaced with H+ in order to maintain electrical neutrality.
Charles C. Mitchell. Extension Agronomist-Soils & Professor
Auburn University
http://hubcap.clemson.edu/~blpprt/acidity2_review.html ….. Diunduh 27/2/2012
PENGAPURAN TANAH MASAM
Soils are limed to reduce the harmful effects of low pH (aluminum or
manganese toxicity) and to add calcium and magnesium to the soil. The
amount of lime needed to achieve a certain pH depends on (1) the pH of
the soil and (2) the buffering capacity of the soil.
The buffering capacity is related to the cation exchange capacity (CEC).
The higher the CEC, the more exchangeable acidity (hydrogen and
aluminum) is held by the soil colloids. As with CEC, buffering capacity
increases with the amounts of clay and organic matter in the soil. Soils
with a high buffering capacity require larger amounts of lime to increase
the pH than soils with a lower buffering capacity.
Most soil testing laboratories use a special buffered solution to measure
the exchangeable acidity. This is the form of soil acidity that must be
neutralized for a change in soil pH. By calibrating pH changes in the
buffered solution with known amounts of acid, the amount of lime
required to bring the soil to a particular pH can be determined.
Lime reduces soil acidity (increases pH) by changing some of the
hydrogen ions into water and carbon dioxide (CO2). A Ca++ ion from the
lime replaces two H+ ions on the cation exchange complex. The carbonate
(CO3-) reacts with water to form bicarbonate (HCO3-). These react with H+
to form H2O and CO2. The pH increases because the H+ concentration has
been reduced.
H+ Soil Colloid + CaCO3 -----Soil Colloid-Ca++ + H2O + CO2
Remember, the reverse of the above process can also occur. An acid soil
can become more acid as basic cations such as Ca2+, Mg2+, and K+ are
removed, usually by crop uptake or leaching, and replaced by H+.
Charles C. Mitchell. Extension Agronomist-Soils & Professor
Auburn University
http://hubcap.clemson.edu/~blpprt/acidity2_review.html ….. Diunduh 27/2/2012
BAHAN PENGAPURAN
The most common liming materials are calcitic or dolomitic agricultural
limestone. These are natural products made by finely grinding natural
limestone. Since natural limestone is relatively insoluble in water,
agricultural limestone must be very finely ground so it can be
thoroughly mixed with the soil and allowed to react with the soil's
acidity. Calcitic limestone is mostly calcium carbonate (CaCO3).
Dolomitic limestone, according to most state laws, must have at least 6
percent magnesium, and is made from rocks containing a mixture of
calcium and magnesium carbonates. Either will neutralize soil acidity.
Dolomitic limestone also provides magnesium.
Material
Some common soil liming materials.
Relative
Neutralizing value
Comment
----------- % -----------100
not generally available
Calcitic agricultural lime,
(calcium carbonate,
CaCO3 +impurities)
90 - 100
easily available
Dolomitic agricultural lime,
CaCO3 + MgCO3
95 - 108
easily available; provides Mg
pure CaCO3
Ground oyster shells
Selma chalk/marl,
CaCO3 + clay
Burned lime, CaO
Hydrated lime or
builders' lime, Ca(OH)2
85 - 95
50 - 85
contains clay; keep dry
150 - 175
very caustic; don't use
120 - 135
caustic; use with caution; no Mg
50 - 70
contains some P & micronutrients;
byproduct
40 - 70
provides some plant nutrients
30 - 60
provides some plant nutrients
By-products
Variable
use as specified by manufacturer
Gypsum and/or
ground drywall, CaSO4
0
NOT A LIMING MATERIAL
Basic slag
Wood stove or fireplace
ashes
Boiler wood ash
Charles C. Mitchell. Extension Agronomist-Soils & Professor
Auburn University
http://hubcap.clemson.edu/~blpprt/acidity2_review.html ….. Diunduh 27/2/2012
Liming to Increase Soil pH
A.M. JOHNSTON¹ and R. DOWBENKO²
¹ Potash & Phosphate Institute of Canada, Saskatoon, Saskatchewan
² Agrium Inc., Calgary, Alberta
The desirable pH range for optimum corn production is 6.0 to 6.5. Soils with a
pH 0.2 to 0.3 units below the recommended level should be considered for
liming. Liming to maintain an optimum soil pH has several benefits. It reduces
the risk of toxicity from aluminum (Al) and other metals, improves the physical
condition of the soil, stimulates microbial activity, increases the cation exchange
capacity (CEC) in some variable charge soils, increases the availability of several
nutrients such as N, P, and molybdenum (Mo), supplies Ca and Mg for plants,
and improves symbiotic N fixation by legume rotation crops such as alfalfa and
soybeans. Calcitic and dolomitic aglime are the most common lime sources.
Yield response of corn to soil pH.
(From Lathwell and Reid. 1984. In F. Adams, ed. Soil Acidity and LimingAgronomy
Monograph 12, 2nd Edition. American Society of Agronomy).
http://www.farmwest.com/index.cfm?method=library.showPage&librarypageid=135…..
Diunduh 27/2/2012
BENTUK-BENTUK KEMASAMAN TANAH
(i) Kemasaman aktif
Refers only to H+ and not Al3+ in the soil solution
(ii) Kemasaman-tukar = Exchangeable acidity
Includes exchangeable Al3+
Includes exchangeable H. Usually there is a small amount in acid mineral soils
but it is more abundant in organic soils
It is extracted with a neutral unbuffered salt solution, such as KCl, CaCl 2 or NaCl
(iii) Kemasaman residual atau Non-exchangeable
This is comprised of weak acids not replaced by neutral unbuffered salt solution
and H+ which bonds with OH-. This is the type of acidity caused by organic
matter and bound Al. Bound Al occurs in soils primarily as Al polymers (long
chain compounds) and is denoted as Al (OH)xx+
Al (OH)xx+ + OH- ------- Al (OH)xx+
COOH + OH- --------- COO- + H2O
http://hubcap.clemson.edu/~blpprt/acid1.html….. Diunduh 27/2/2012
TAPAK PERTUKARAN KATION
Al-tukar dan Kation-tukar
Soil chemists have defined exchangeable cations in acid soils as those
cations extracted with a neutral unbuffered salt solution. The sum of
these cations is termed the effective cation exchange capacity. A neutral
unbuffered salt solution will extract only cations that are held at active
exchange sites at a particular pH of the soil. The exchangeable acidity
extracted from soils with a neutral unbuffered salt is Al.
Acid mineral soils at pH 5.0 have their active exchange sites occupied
by Al and at pH 6.0 these sites are countered by exchangeable bases.
The relative cation saturations have an important effect on the cation
composition of the soil solution and in turn on plant growth.
Cation composition of the exchange sites as related to the soil pH
value.
pH
Al
Ca + Mg + K
CEC
meq/100g
4.5
0.91
0.20
1.11
5.4
0.34
0.91
1.25
5.9
0.10
1.60
1.70
http://hubcap.clemson.edu/~blpprt/acid1.html….. Diunduh 27/2/2012
KOMPOSISI LARUTAN TANAH
Aluminum
The concentration of Al in the soil solution is related to pH of the soil, the Al saturation of
effective cation exchange capacity, and the salt concentration of the system. At a pH of 5.5
the concentration of Al in the soil solution is quite low. However, as the pH drops from 5.0 to
4.5, the Al concentration increases markedly.
The Al concentration of the soil solution is related to the Al saturation of the effective CEC of
the soil. The concentration of Al in the soil solution is low until the exchangeable Al
saturation exceeds 60% and then increases rapidly. When the Al saturation is greater than
60%, the soil solution concentration of Al is greater than 1 ppm and may be as high as 5 or 6
ppm.
Manganese
Water-soluble Mn content of acid soils is closely related to the soil pH, being
high below pH 5.0 but decreasing rapidly as the pH value increases to 6.0.
Calcium
The predominant cation in the soil solution of most acid soils is Ca.
Concentrations of soil solution Ca are increased considerably when acid
soils are limed.
http://hubcap.clemson.edu/~blpprt/acid1.html ….. Diunduh 27/2/2012
PEMBENTUKAN Aldd
Clays with hydrogen ion on the exchange complex are not stable.
The aluminosilicate structure decomposes to form Al saturated
clays. Aluminum and basic cation content of different soils.
Notice the difference in aluminum saturation even though the pH
values are approximately the same.
Al
Ca + Mg
+K
%Alsatura
tion
------------ meq/100g -----------
Soi1
pH
Norfolk
4.5
0.91
0.20
82
Lynchburg
4.6
1.96
0.46
81
Portsmouth
4.7
4.18
3.63
54
http://hubcap.clemson.edu/~blpprt/acid1.html….. Diunduh 27/2/2012
ASAL-USUL KEMASAMAN TANAH
Serapan Ca dan Mg oleh Tanaman
Rainfall in excess of evapotranspiration (leaching) removes Ca
and Mg from the soil. Soils of humid regions usually contain
little weatherable Ca and Mg minerals.
http://hubcap.clemson.edu/~blpprt/acid1.html….. Diunduh 27/2/2012
ORIGIN OF SOIL ACIDITY
SERAPAN TANAMAN
Calcium and magnesium composition of some crops.
Ca
Crop
Mg
lbs/ton of crop
Dicots
Alfalfa
Lespedeza
Red clover
Soybean
Monocots
K. bluegrass
Timothy
Corn stover
Wheat straw
35.0
17.0
29.4
25.0
9.8
5.7
9.2
17.4
6.2
5.6
9.8
3.2
4.0
3.6
8.4
2.2
http://hubcap.clemson.edu/~blpprt/acid1.html….. Diunduh 27/2/2012
ASAL-USUL KEMASAMAN TANAH
Penambahan Hidrogen
i.) From the decomposition of organic matter
ii.) Roots take up basic cations and exchange them with H
iii.) Acid forming fertilizers
2NH4+ (ammonium) + 4O2 2NO3- (nitrate) + 4H+ (acidic hydrogen)
+ 2H2O Estimates of 1.8 to 3.6 lb of CaCO3 is required to
neutralize the acidity generated from 1 lb of NH4+ nitrogen:
Acidity generated from common N sources
lb CaCO3/lb N
needed to
Nitrogen Source
neutralize the
acidity
Anhydrous ammonia
1.8
Urea
1.8
Ammonium nitrate
1.8
Ammonium sulfate
5.4
5.4
Monoammonium phosphate
Diammonium phosphate
3.6
http://hubcap.clemson.edu/~blpprt/acid1.html….. Diunduh 27/2/2012
MANFAAT PENGAPURAN
Liming will provide the following benefits:
1.
2.
3.
4.
5.
6.
reduces the possibility of Mn2+ and Al3+ toxicity;
improves microbial activity;
improves physical condition (better structure);
improves symbiotic nitrogen fixation by legumes;
improves palatability of forages;
provides an inexpensive source for Ca2+ and Mg2+
when these nutrients are deficient at lower pH;
7. improves nutrient availability (availability of P and
Mo increases as pH increases at 6.0 – 7.0, however,
other micronutrients availability increases as pH
decreases).
http://soils.usda.gov/sqi/management/files/sq_atn_8.pdf….. Diunduh 27/2/2012
Crops require different pH levels (adapted from Tisdale
et al., 1993).
http://soils.usda.gov/sqi/management/files/sq_atn_8.pdf….. Diunduh 27/2/2012
BAHAN KAPUR PERTANIAN
Liming materials are usually Ca and or Mg carbonates, oxides, and
hydroxides.
Liming materials are effective when they:
• remove H+ and Al+ off of exchange sites (potential acidity);
• neutralize H+ in solution (active acidity);
• are economical.
In order for liming material to be economical, it generally has to be a
salt. A strong base and strong acid such as NaCl (sodium chloride) or
CaSO4 (gypsum) are not effective in raising pH levels because a
hydroxyl (OH-) is not released to neutralize H+ by forming water
(H2O).
A salt of a strong base and a weak acid is required to raise pH as
shown by the equation below.
CaCO3 + H2O ↔ Ca2+ + HCO3- + OHThe Ca2+ displaces H+ and Al3+ on exchange sites where OHneutralizes the H+ in solution.
The effectiveness of liming material is based on two factors:
• Calcium Carbonate Equivalent (CCE) and
• fineness of material
These two factors when combined are called the Effective Calcium
Carbonate (ECC).
http://soils.usda.gov/sqi/management/files/sq_atn_8.pdf….. Diunduh 27/2/2012
MENENTUKAN NILAI CCE
The CCE is a way to relate all liming materials to CaCO3 as a standard.
The molecular weight of CaCO3 is 100 (Ca = 40, C =12, and O =16 x 3).
The CCE of CaCO3 has been theoretically established at 100. When using
other materials other than CaCO3, the molecular weight of CaCO3 is
divided by the other material’s molecular weight.
For example, the calculation for the use of wood ash as a liming material is
as follows:
Wood ashes (K2CO3) molecular weight = 138
CaCO3 = 100
100/138 = 0.72 (CCE) or 72% effective compared to CaCO3
So if a recommendation from a soil called for 1,000 lbs. of agricultural lime
(CaCO3), then you would divide the CCE of 0.72 (K2CO3) into the rate
needed to determine the amount of K2CO3 needed.
1,000 lbs. CaCO3 / 0.72 = 1,389 lbs. of K2CO3
In this case 1,389 lbs. of K2CO3 are needed to achieve the same effect as
1,000 lbs. of calcium carbonate.
Neutralizing Value (CCE) of Liming Materials (Tisdale et al., 1993)
http://soils.usda.gov/sqi/management/files/sq_atn_8.pdf….. Diunduh 27/2/2012
BAGAIMANA KAPUR MENAIKKAN pH TANAH
Limestone is calcium carbonate and magnesium carbonate:
CaCO3 and MgCO3
The limestone dissolves in water to form carbonic acid (H2CO3)
and calcium hydroxide (Ca(OH)2):
CaCO3 + H2O ↔ H2CO3 + Ca(OH)2
Carbonic acid is unstable and converts to carbon dioxide (CO2) and
water; the CO2 gas escapes:
H2CO3 ↔ CO2 + H2O
The remaining calcium hydroxide dissociates:
Ca(OH)2 ↔ Ca2+ + 2OHThe Ca2+ replaces 2H+ from the soil, increasing the soil base
saturation
The hydroxide anion (OH-) reacts with the soil acid cation (H+),
forming water:
OH- + H+ ↔ H2O
http://nrcca.cals.cornell.edu/nutrient/CA5/CA0540.php ….. Diunduh 27/2/2012
REAKSI KAPUR DALAM TANAH
http://nrcca.cals.cornell.edu/nutrient/CA5/CA0539.php ….. Diunduh 27/2/2012
PENGAPURAN MENINGGKATKAN KETERSEDIAAN
HARA
Soil pH affects nutrient availability by changing the form of the nutrient in
the soil. Adjusting soil pH to a recommended value can increase the
availability of important nutrients. Plants usually grow well at pH values
above 5.5. Soil pH of 6.5 is usually considered optimum for nutrient
availability.
Lower pH increases the solubility of Al, Mn, and Fe, which are toxic to
plants in excess. A critical effect of excess soluble Al is the slowing or
stopping of root growth.
Extreme pH values decrease the availability of most nutrients. Low pH
reduces the availability of the macro- and secondary nutrients, while high
pH reduces the availability of most micronutrients. Microbial activity may
also be reduced or changed.
http://nrcca.cals.cornell.edu/nutrient/CA5/CA0539.php ….. Diunduh 27/2/2012
REAKSI KAPUR DALAM TANAH
Lime supplies a surplus of the basic cations Ca2+ and/or Mg2+ in a
carbonated, hydroxide, or oxide form (CaCO3, MgCO3, CaOH, MgOH,
CaO). As the compounds dissolve in soil solution, the carbonate (CO 32-),
hydroxyl (OH-), or oxide (O2-) react with active acidity (H+) to form
carbonic acid (H2CO3) or water (H2O). Also, because H+ is being removed
from soil solution, free Al3+ reacts with OH- to form an insoluble
compound.
Hydrogen held by soil-clay (potential acidity) is released into soil solution
to maintain chemical equilibrium as active acidity is neutralized, and Al3+ is
released from the soil to form insoluble compounds. The H+ released into
the soil solution is then neutralized until the CO32-, OH-, and O2- are
exhausted. Ultimately, most of the carbonic acid will dissociate to form
water and carbon dioxide. Thus, excess H+ is converted into water, and free
Ca2+ and/or Mg2+ replace the released H+ and Al3+ on the soil exchange sites
http://ohioline.osu.edu/agf-fact/0505.html ….. Diunduh 27/2/2012
TNP = Total Neutralizing Power
Total Neutralizing Power (TNP) is a measure of the ability
of a liming material to raise the pH. The percentage of
calcium, percentage of magnesium, and impurities, such as
silt and clay, determine TNP.
Pure calcium carbonate has a neutralizing power of 100:
other liming materials are compared on a percentage basis
with it.
The two major liming materials are dolomitic and calcitic
limestone. Both are sources of calcium and magnesium, but
the percentage of each varies and thus the TNP varies.
Dolimitic limestone contains approximately 20 to 22%
calcium and 11 to 13% magnesium.
Because of molecular weight differences, magnesium
carbonate on a pound for pound basis is 16% more effective
in raising the pH than calcium carbonate.
Therefore the TNP will normally range from 100 to 110 for
dolomitic limestone. Calcitic or hical lime contains
approximately 32 to 35% calcium, 2 to 5% magnesium, and
has a TNP of 90 to 99.
http://ohioline.osu.edu/agf-fact/0505.html ….. Diunduh 27/2/2012
Total neutralizing power (TNP), fineness, water content, and
ENP of common liming materials.
Grade
TNP (%)
8
Fineness
% passing mesh size
20
60
Water (%)
ENP
(lbs/ton)
FI
Aglime
superfine
100
100
100
100
100
0
2000
Dolomitic
hydrated
aglime
140
100
99
76
90
0
2520
Calcitic
aglime
99
99
60
37
59
0
1168
Dolomitic
aglime
105
97
95
90
93
0
1953
Waste water
lime
102
100
100
100
100
74
530
Pelletized
lime
93
100
100
100
100
0
1860
These are liming materials available in the state of Ohio. Depending upon source, lime characteristics
will vary.
ENP = effective neutralizing power
In Ohio, liming materials are labeled based on their effective neutralizing power
(ENP), which is reported in lbs/ton. The ENP considers the total neutralizing
power (TNP), fineness of grind, and percent moisture of a liming material (Ohio
Aglime Council, 2003), and may be calculated by Equation 1.
Equation 1:
ENP (lbs/ton) = TNP/100 * FI/100 * %DW/100 * 2000 lbs/ton
http://ohioline.osu.edu/agf-fact/0505.html ….. Diunduh 27/2/2012
REKOMENDASI KAPUR
Once it has been determined that liming is necessary by soil pH and the buffer pH
measurement, a lime recommendation can be made. Reported lime rates assume an effective
neutralizing power (ENP) of 2000 lb/ton and an incorporation depth of 8 inches. To compute
the application rate of a lime source with an ENP different from 2000 lb/ton use Equation :
Tons of material / A = LR * (2000 / ENP)
If depth of incorporation is different than 8 inches, divide the lime recommendation by 8
and multiply by the new depth. For example, assume the lime rate needed is 1.6 t/A from
Table 4. The lime will be incorporated into the top 6 inches, so the new rate of lime is 1.2
t/A, (i.e., 1.6/8 x 6 = 1.2).
Tons of liming material (ENP of 2000 lbs/ton) needed to raise the soil pH to the desired
pH level based on the SMP (Shoemaker-McLean-Pratt) buffer and an incorporation
depth of 8 inches (adapted from Tri-State Fertilizer Recommendations, 1996)
Desired pH levels
Mineral soils
6.82
6.53
Organic soils
6.04
Soil pH
5.3
Buffer pH1
tons agricultural limestone/acre
tons/acre
6.8
0.9
0.8
0.7
5.2
0.0
6.7
1.6
1.4
1.1
5.1
0.5
6.6
2.2
2.0
1.6
5.0
0.8
6.5
2.9
2.5
2.0
4.9
1.3
6.4
3.6
3.1
2.5
4.8
1.7
6.3
4.2
3.6
3.0
4.7
2.1
6.2
4.9
4.2
3.4
4.6
2.5
6.1
5.6
4.7
3.9
4.5
2.9
6.0
6.2
5.3
4.4
4.4
3.3
1.To compute LTI multiply buffer pH by 10.
2.For desired pH of 6.8: lime recommendation = -6.8*buffer pH + 46.8
3.For desired pH of 6.5: lime recommendation = -5.6*buffer pH + 39.1
4.For desired pH of 6.0: lime recommendation = -4.6*buffer pH + 31.8
http://ohioline.osu.edu/agf-fact/0505.html ….. Diunduh 27/2/2012
Lime Recommendations for Field Crops
Lime recommendations depend on:
1. Current and desired pH.
2. Exchangeable acidity.
3. Base saturation of the soil at the
current and at the desired pH.
4. Tillage depth.
Base saturation is the amount of basic cations divided by the total cation
exchange capacity (total number of cation exchange sites). So, if the base
saturation is 0.75, 75% of the cation exchange capacity is occupied by
Ca2+, Mg2+, K+ and/or Na+ while 25% is exchangeable acidity. For soils
with a pH of 6.0 or lower, the lime recommendation is determined by the
exchangeable acidity, base saturation at the original pH and at the desired
pH, and the tillage depth (TD, inches):
(BSdesired-BSoriginal)
Lime Req. = EA*0.5*---------------------------------------- * (TD/6)
(1-BSorginal)
Where the pH of the soil is 6.1 or higher, the exchangeable acidity is
negligible but there is still residual acidity. For these soils, the exchangeable
acidity measurement needs to be replaced by estimated cation exchange
capacity (CEC).
http://www.nnyagdev.org/PDF/LimeRecommendations.pdf….. Diunduh 27/2/2012
Lime and Nutrient Recommendations
Soil pH and Lime Recommendations
Soil-water pH provides a measure of active acidity in soil,
and soil-buffer pH provides a measure of reserve acidity in soil.
Soil-water pH can be lower than expected in the fall after a dry
growing season due to salts from fertilizer not being leached
out. To avoid the lower than expected soil-water pH, active
acidity is measured in a solution with a high salt concentration
(1 M KCl), which removes variable soil-salt levels occurring at
much lower concentrations in the soil. The soil pH measured
in 1 M KCl is about 1 pH unit lower than soil-water pH. Since
soil-water pH is a much more familiar value in relationship to
optimum plant growth, the measurement of 1 M KCl soil pH is
converted to soil-water pH for presentation on soil test reports.
Lime recommendations, however, are based on 1 M KCl soil pH.
To determine how much lime is required to raise soil-water
pH, see tables 6, 7, or 8 with the target pH of 6.4, 6.6, or 6.8 in the
heading. The soil-water pH is shown as the first column, and the
buffer pH is shown as the top row of pH values. To determine
the appropriate lime rate, read down the first column to the
samples soil-water pH then read across to the samples buffer
pH. The lime rates were determined from a lime response curve
using 1 M KCl soil pH and buffer pH with a correction
factor for field application. The resultant lime rates are
rounded to the nearest 0.25 tons/acre.
http://www.ca.uky.edu/agc/pubs/agr/agr1/agr1.pdf….. Diunduh 27/2/2012
Lime and Nutrient Recommendations
Soil pH and Lime Recommendations
Rate of 100% effective limestone (tons/acre) needed to raise soil pH to 6.4.
Rate of 100% effective limestone (tons/acre) needed to raise soil pH to 6.6.
http://www.ca.uky.edu/agc/pubs/agr/agr1/agr1.pdf….. Diunduh 27/2/2012
PENGARUH PENGAPURAN TERHADAP BIOLOGI
TANAH
Mean millipede and snail abundance (number per 25 m2) with SE bars on limetreated and control sites with model lines. Lime treatment was applied between
2003 and 2004 in central Pennsylvania. *Confidence intervals of the time-bytreatment interaction excluded zero, indicating a significant effect of liming on
that variable.
http://www.hindawi.com/journals/ijfr/2012/976809/fig2/ ….. Diunduh 27/2/2012
PENGARUH PENGAPURAN TERHADAP HASIL
TANAMAN
Effects of Liming on Canola Yields at 27 Alberta Sites on Soils with Different
pH Ranges .
The canola yields on acid soils can be substantially increased by lime
application.
The increase in soil pH resulting from lime application provides a more
favourable environment for soil microbiological activity that increases the rate
of release of plant nutrients, particularly nitrogen. Reduced soil acidity
following liming also increases the availability of several other plant nutrients,
notably phosphorus.
One of the benefits of liming acid soils is the increased utilization of residual
fertilizer phosphorus by crops. On slightly acid (pH 6.1 to 6.5) and moderately
acid (pH 5.6 to 6.0) soils, liming will have a minor effect on canola yields
http://www.canolacouncil.org/chapter6.aspx ….. Diunduh 27/2/2012
PENENTUAN KEBUTUHAN KAPUR
Soil acidity consists of active and reserve acidity. Most of
the acid-causing elements (hydrogen and aluminum) are held
by the cation exchange sites of the soil particles and organic
matter. This is referred to as reserve acidity. Soils with large
amounts of clay and organic matter have high potential for
reserve acidity.
Soil pH is a measure of active acidity, the hydrogen ion
concentration in the soil solution. The higher the
concentration of hydrogen ions in soil solution, the lower the
pH (i.e., greater acidity). The active acidity is present in the
immediate environment of roots and microbes. The total
acidity is the sum of the reserve and active acidity.
Lime neutralizes both the active acidity and some of the
reserve acidity. As active acidity is neutralized by the lime,
reserve acidity is released into the soil solution, maintaining
the active acidity or the pH.
The ability of a soil to resist changes in pH is called
buffering capacity and is largely due to the reserve acidity.
More lime is required to neutralize acidity on a highly
buffered soil compared to a less buffered soil
http://www.ianrpubs.unl.edu/pages/publicationD.jsp?publicationId=112 ….. Diunduh
27/2/2012
Examples of approximate lime required to raise the pH
of soils of different textural classes. (Source: Nutrient
Management for Agronomic Crops in Nebraska, EC155,
UNL Extension.)
Soil
texture
Loamy
sand
Silt loam
Silty clay
loam
CEC
(meq/100
g)
Soil
pH
Buffer
pH
Lime rate
(tons/acre)
6
14
24
5.6
5.5
5.6
6.8
6.6
6.2
1
2
4
http://www.ianrpubs.unl.edu/pages/publicationD.jsp?publicationId=112 ….. Diunduh
27/2/2012
KUALITAS BAHAN KAPUR
Two factors determine the effectiveness (ECCE) of liming materials:
1.
neutralizing value or purity, also referred to as calcium carbonate
equivalent (CCE)
2.
particle size or fineness of the liming material.
The neutralizing value, or CCE, is the amount of acid on a weight basis that
a given quantity of lime will neutralize when dissolved. It is expressed as a
percentage of the neutralizing value of pure calcium carbonate or calcite
(100 percent CCE). A lime that neutralizes 80 percent as much acid as pure
calcium carbonate is said to have a CCE of 80. Table III shows the CCE of
different liming materials.
Calcium carbonate equivalent (CCE) of liming materials.
Material %
CCE*
Pure calcite
100
Calcitic lime
75-100
Dolomitic lime
75-109
Hydrated lime
120-136
Burned lime
179
Pel-lime (finely ground ag-lime)
90-95
Fly ash**
43-44
Wood ash
30-70
*These values only consider the purity of the material, however, the fineness
also must be considered to determine the effectiveness of the lime (i.e.,
ECCE = CCE times fineness).
**Based on UNL research on ash from power plants in Nebraska. Fly ash
CCE values and other chemical analyses should be done due to variation
caused by source of coal, collection procedures and other factors.
http://www.ianrpubs.unl.edu/pages/publicationD.jsp?publicationId=112 ….. Diunduh
27/2/2012
BENEFICIAL EFFECTS FROM LIMING
Soil acidity has a direct effect upon availability of most essential
plant nutrients.
The general effect of pH on plant nutrient availability. The best pH
range for most nutrients is between 6.0 and 7.0. Deficiencies can be
observed at both low and high pH's. Manganese and iron exhibit
toxicity at low pH's and deficiency at high pH levels. Although
aluminum is not an essential nutrient, it is important because it
rapidly increases in solubility as the soil pH drops below 5.0. Too
much aluminum in solution will restrict root and plant
development.
Effects of change in soil pH on the availability of plant nutrients.
http://www.agry.purdue.edu/ext/forages/publications/ay267.htm ….. Diunduh 27/2/2012
KEBUTUHAN pH TANAMAN
Normal crop growth occurs over a range in pH values and
the range varies by crop. In a soil testing laboratory, the
necessity for limestone is based on crops to be grown, soil
pH, and soil organic matter (mineral soil vs. organic soil).
The goal of a liming program is to apply enough aglime to
raise the soil pH to the middle of the range for normal
growth and then reapply when it drops below the range.
Mineral soil pH ranges for crops.
http://www.agry.purdue.edu/ext/forages/publications/ay267.htm ….. Diunduh 27/2/2012
BENEFITS PROVIDED BY LIMING SOILS INCLUDE:
1.
2.
3.
4.
5.
6.
7.
Improved availability of soil nutrients such as phosphorus,
potassium, nitrogen, calcium, magnesium, sulfur, boron, and
molybdenum.
Increased efficiency of fertilizers applied to the soil.
Reduced availability of aluminum and manganese, which may
cause toxicity problems in acid conditions.
More favorable microbial activity in the soil.
Better soil structure and tilth.
Increased longevity of legume stands such as alfalfa and clovers.
Improved activity of certain herbicides, providing better weed
control.
Effect of soil acidity on soybean yields. Missouri Agricultural
Experiment Station Bulletin 947. T.R. Fisher.
http://extension.missouri.edu/p/G9102….. Diunduh 27/2/2012
Pasture responses to lime over five years are limited and highly
variable
A.E. Crawford and C.J.P. Gourley
Agriculture Victoria Ellinbank, Department of Natural Resources and Environment, Victoria.
Effect of lime on soil pH(H2O), exchangeable Al (KCl), available P
(Olsen) and extractable cations at Wyelangta in October 1999, five
years after application. Depths shown are 0-5 cm (), 5-10 cm (), 10-15
cm () and 15-20 cm ().
http://www.regional.org.au/au/asa/2001/3/b/crawford.htm….. Diunduh 27/2/2012
Grain yield responses to liming obtained at Rutherglen,
North-east Victoria, 1984 season.
http://regional.org.au/au/asa/1985/invited/p-12.htm….. Diunduh 27/2/2012
EFEK PENGAPURAN TERHADAP HASIL
Effect of calcium carbonate on dry matter output from a
surface seeded grass-clover sward (source O’Toole 1968)
Liming to neutral state is expensive and unnecessary. It may affect
the availability of trace elements and over-liming may influence
denitrification, producing toxic levels of nitrate-nitrogen.
O’Toole (1968) showed that where an adequate supply of nitrogen
fertilizer is applied to pasture the pH can be maintained at lower
levels than where no applications are given. The influence of
liming on the dry matter output of a mixed grass-clover sward.
http://www.fao.org/docrep/x5872e/x5872e0a.htm….. Diunduh 27/2/2012
PENGAPURAN TANAMAN JAGUNG
Cumulative yields of maize over three years at a site in
Brazil, as affected by lime rates and depth of lime
incorporation (CPAC 1976).
A yield increase in corn after lime incorporation to 30 cm
compared to 15 cm
http://www.regional.org.au/au/roc/1986/roc198607.htm….. Diunduh 27/2/2012
Responses of Corn and soybeans to liming on
mineral soils
A major reason for crop response to lime is due to the
precipitation of exchangeable Al
The beneficial effects of liming on crop growth are often
related to neutralization of Al and not directly to the
change in pH.
Yield
pH
% Al
Saturation
Corn
Soybeans
bu/a
5.0
77
127
18
5.5
25
143
40
6.0
15
143
40
http://hubcap.clemson.edu/~blpprt/acid3.html….. Diunduh 27/2/2012
METODE KEBUTUHAN KAPUR
The Adams and Evans buffer (used by Alabama, Florida, Georgia, Tennessee,
South Carolina, and Virginia) was developed for soils with low cation
exchange capacity and containing primarily kaolinitic clays.
These soils usually have relatively low lime requirements and the possibility
of overliming exists.
The Adams and Evans buffer is very reliable for soils with relatively small
amounts of exchangeable acidity and provides a fairly high degree of accuracy
of estimating lime requirements to reach pH 6.5 or less. Sensitivity of the lime
requirement by this method is within 500 lb/A of limestone.
The Adams and Evans lime requirement method is based on separate
measurements of soil pH in water and a buffer solution (pH 8.0) The soil pH
determination is used as a measure of acid saturation of the soil (H-sat1)
according to the following equation:
Measured soil pH = 7.79 5.55 (H-sat1) + 2.27 (H-sat1)2
Where H-saturation is expressed as a fraction of the CEC. Buffer pH is used as
a measure of soil acids (Soil H) according the following equation:
Soil H = 8(8.00 buffer pH)
The desired soil pH is expressed in terms of acid saturation of the soil (H-sat2)
according to the following equation:
Desired soil pH = 7.79 5.55 (H-sat2) + 2.27 (H-sat1)2
The Adams-Evans buffer method assumes that agricultural-grade limestone is
about 2/3 effective in neutralizing soil acidity up to a soil pH of about 6.5, and
allows for this by using a correction factor of 1.5. Thus, the lime requirement
is the product of the following equation:
Soil H/H-sat1 x (H-sat1 (H-sat2) x 1.5
or for 10 cm3 soil in 10 ml water + 10 ml buffer solution, the lime
recommendation is:
Limestone (lbs/A) = 8000[(8.00 - buffer pH)/H-sat1] x (H-sat1 - H-sat2) x 1.5
http://hubcap.clemson.edu/~blpprt/diagnosis.html….. Diunduh 27/2/2012
METODE KEBUTUHAN KAPUR
As noted above lime requirement calculations using the
Adams-Evans method is based on two pH determinations,
soil pH and buffer pH. With this information and the
formulas above the lime requirement of a soil can be
calculated. The following table is an abbreviated example of
the lime requirement for a soil depth weighing 2,000,000
pounds per acre to increase soil pH to 6.5.
Soil pH in Buffered Solution
Soil pH
in water
7.9
7.80
7.70
7.60
7.50
7.40
7.30
6.3
183
366
549
732
915
1098
1281
6.1
324
648
972
1295
1619
1943
2267
5.9
436
872
1308
1744
2180
2616
3052
5.7
528
1056
1584
2112
2641
3169
3697
5.5
605
1211
1816
2422
3027
3633
4238
5.3
672
1344
2016
2689
3361
4033
4705
5.1
731
1462
2193
2924
3655
4386
5117
4.9
785
1569
2354
3138
3923
4707
5492
4.7
836
1672
2507
3343
4179
5015
5850
*Note: The depths of soil it takes to weigh 2,000,000 pounds will vary with the bulk
density of the soil. For example, a sandy loam soil with a bulk density of 1.472 would
weigh 2,001,232 pounds per 6 inch-depth, whereas, a loam soil with a bulk density of
1.299 would weigh 2,001,504 pounds per 6.8 inch-depth.
http://hubcap.clemson.edu/~blpprt/diagnosis.html….. Diunduh 27/2/2012
METODE MEHLICH
The Mehlich buffer method (used by North Carolina) was
developed to determine the amount of lime required to
neutralize the acidity extracted with an unbuffered salt
solution. This approach was based on neutralizing the acidity
that is limiting crop growth and not trying to achieve a given
pH. A buffer solution of pH 6.6 is used to measure
extractable acidity (Ac). The buffered solution extracts both
exchangeable Al and the pH dependent acidity (H) which
becomes ionized up to pH 6.6. The lime rate to apply is
calculated with the following equation:
CaCO3 tons/acre = Ac (desired pH - soil pH)
(6.6 - soil pH)
The desired pH for a soil is the pH at which the activity of
Al is neutralized. The effect of soil organic matter in
decreasing the activity of Al has been taken into account by
establishing desired pH's for three classes of soils based on
their organic matter content: mineral, mineral-organic and
organic. The desired pH at which exchangeable Al is
essentially neutralized is 6.0 for mineral soils, 5.5 for
mineral-organic soils and 5.0 for organic soils.
http://hubcap.clemson.edu/~blpprt/diagnosis.html….. Diunduh 27/2/2012
REAKSI KAPUR DALAM TANAH
When lime (i.e., CaCO3) is added to a moist soil, the
following reactions will occur:
(1) Lime is dissolved slowly by moisture in the soil to
produce Ca2+ and OHCaCO3 + H2O (in soil) ==> Ca2+ + 2OH- + CO2 (gas)
(1) Newly produced Ca2+ will exchange with Al3+ and H+
on the surface of acid soils
2Ca2+ + soil-Al ===> soil-Ca + Al3+ + soil-H soil-Ca + H+
(1) Lime-produced OH- will react with Al3+ to form
Al(OH)3 solid and with H+ to form water.
Al3+ + 3OH- ===> Al(OH)3 (solid) H+ + OH- ===> H2O
http://www2.hawaii.edu/~nvhue/acid.html….. Diunduh 27/2/2012
Relationships between permanent and pH
dependent charge
http://courses.soil.ncsu.edu/ssc051/chapters/print2_2.html….. Diunduh 27/2/2012
EFEK pH dan Al terhadap tanaman
At low soil pH Aluminum ions make up a large fraction of the cations. As
soil pH approaches 4.5, exchangeable Aluminum ions per se, disappear, and
above pH 6 there are few Aluminum ions potentially available.
The table below reports data from a Bordeaux study on the affects of
Aluminum ions on growth of Cabernet Sauvignon (V. vinifera) grapevines.
Note that only 10 ppm (mg/l) in solution reduced vine growth almost in
half. The aluminum ions are not absorbed by the roots, and they do not
enter the vine. Aluminum ions directly inhibit root growth. Thus aluminum
toxicity cannot be detected from petiole mineral element analysis. Vine
roots must be inspected.
http://www.fruit.cornell.edu/grape/pool/nutrition.html….. Diunduh 27/2/2012
EFEK PENGAPURAN thd Al
the addition of lime to an acid soil raises the pH
and decreases aluminum availability.
Effects of Lime Addition on Extractable Aluminum of a
Bordeaux, France Soil
Soil pH
Extractable
Aluminum
(mg/kg)
Control
4.1
328
2.8 tons/acre CaO
5.1
54
3.7 tons/acre CaO
5.5
28
5.5 tons/acre CaO
6.1
Trace
Soil Treatment
Source: Delmas, Pont-de-la-Maye, 1984
http://www.fruit.cornell.edu/grape/pool/nutrition.html….. Diunduh 27/2/2012
SOURCE OF ELECTROSTATIC
CHARGE
Isomorphic substitution
Al3+ for Si4+ in the tetrahedral sheet and Mg2+ for
Al3+ in the dioctahedral sheet.
These substitutions occur during formation of the
clay mineral and are permanent to the
structure. Both lead to net negative charge within
the crystal lattice that is balanced by adsorbed
cations.
pH-dependent charge
Loss of ionizable H+ from certain sites on mineral
colloids or from certain functional groups in
humus leads to negatively charged sites.
Protonation of other sites leads to positively
charged sites. pH-dependent negative charge
increases with increasing pH but pH-dependent
positive charge increases with decreasing pH.
http://www.agronomy.lsu.edu/courses/agro2051/chap08.htm….. Diunduh 27/2/2012
Muatan negatif yang trgantung pH
http://www.agronomy.lsu.edu/courses/agro2051/chap08.htm….. Diunduh 27/2/2012
MUATAN NEGATIF TANAH
Influence of pH on CEC of smectite and SOM. Below pH
6 the charge for clay minerals is relatively constant
(permanent CEC charge); above pH 6, contribution of
the variable charge from clay minerals is evident
(ionisation of H + from hydroxy groups). By comparison,
almost all of the charges on the organic colloid are
considered to be pH dependent, i.e. variable charge
(modified from Brady 1990).
http://grdc.com.au/director/events/grdcpublications.cfm?item_id=2E7B554DF79646147F64C
3704857B3EF&article_id=377C1F0CB5E518C97B90EAB21FEA1D74 ….. Diunduh 27/2/2012
pH dependent charge on clay minerals
The permanent negative charge on a clay mineral as a result of
isomorphous substitution does not change with pH. Why? Because the
charge was created when the mineral was formed sand is locked inside
the crystal structure. Increased negative charge, or pH dependent charge,
is caused by ionization of H+ ions (deprotonation) attached to -OH ions
on the surface and edges of the crystal lattice.
Therefore at higher soil pH's the clay minerals have increased capacity
to hold basic cations.
http://agcal.usask.ca/slsc240/modules/module3/clay_charge.html ….. Diunduh 27/2/2012
pH Dependent Charge
The negative charge on clay minerals generally increases
with a rise in the pH of soil solution. This is a result of
deprotonation. Deprotonation is the removal of H+ from
anions such as OH bound at the edges of 2:1 clay minerals or
the surface of 1:1 minerals such as kaolinite. The reaction
can be represented as follows:
In soils there are many other sources of pH dependent
negative charge: from dissociation of H+ from functional
groups on organic matter and also from OH groups attached
to amorphous hydrous metal oxides which often coat the
surfaces of clays and link to organic matter.
http://agcal.usask.ca/slsc240/modules/module3/clay_charge.html ….. Diunduh 27/2/2012
ISOMORPHOUS SUBSTITUTION
During clay formation, the central cation of a silica tetrahedra Si4+
can be replaced (substituted) by similar sized ions such as, Al3+
aluminum or Fe3+ iron (How? See previous section). Similarly,
replacement of the central cation, Al3+, in aluminum octahedra can
also occur. In this case Mg2+ magnesium or Fe2+ iron are the most
common substitutes. This phenomenon is called isomorphous
substitution (literally: "same shape").
2:1 Crystal lattice showing isomorphous substitution and net
negative charge
http://agcal.usask.ca/slsc240/modules/module3/clay_charge.html ….. Diunduh 27/2/2012
Electric Double Layer
Electric Double Layer is the phenomenon playing a fundamental role in the
mechanism of the electrostatic stabilization of colloids.
Colloidal particles gain negative electric charge when negatively charged ions of the
dispersion medium are adsorbed on the particles surface.
A negatively charged particle attracts the positive counterions surrounding the particle.
Electric Double Layer is the layer surrounding a particle of the dispersed phase and
including the ions adsorbed on the particle surface and a film of the countercharged
dispersion medium.
The Electric Double Layer is electrically neutral.
An Electric Double Layer consists
of three parts:
Surface charge - charged ions
(commonly negative) adsorbed on
the particle surface.
Stern layer - counterions (charged
opposite to the surface charge)
attracted to the particle surface and
closely attached to it by the
electrostatic force.
Diffuse layer - a film of the
dispersion medium (solvent)
adjacent to the particle. Diffuse
layer contains free ions with a
higher concentration of the
counterions. The ions of the diffuse
layer are affected by the
electrostatic force of the charged
particle.
http://www.substech.com/dokuwiki/doku.php?id=stabilization_of_colloids&DokuWiki=011a
dd7efefd6f1bd6b9974b3a66990f….. Diunduh 27/2/2012
REAKSI PERTUKARAN KATION
The interchange between a cation in solution and another cation on the
surface of any negatively charged material such as clay or organic matter.
What determines if a cation is on the exchange complex or in the soil
solution?
Cation exchange is influenced by:
1) strength of adsorption--->Strong adsorption » Al+3 > Ca2+ > Mg2+ >
K+=NH4+ > Na+ >H+ »Weak adsorption
2) the relative concentration of the cations in the soil solution.
At any one time the quantity of ions on the exchange compared to what is in
the soil solution is determined by the kind of ions present and the quantity
of ions present in the soil.
http://www.swac.umn.edu/classes/soil2125/doc/s12ch2.htm….. Diunduh 27/2/2012
KTK = KAPASITAS TUKAR KATION
Cation Exchange Capacity (CEC) is the ability of the soil to hold
onto nutrients and prevent them from leaching beyond the roots.
The more cation exchange capacity a soil has, the more likely the
soil will have a higher fertility level. When combined with other
measures of soil fertility, CEC is a good indicator of soil quality
and productivity.
The cation exchange capacity of a soil is simply a measure of the
quantity of sites on soil surfaces that can retain positively charged
ions by electrostatic forces. Cations retained electrostatically are
easily exchangeable with other cations in the soil solution and are
thus readily available for plant uptake. Thus, CEC is important for
maintaining adequate quantities of plant available calcium (Ca++),
magnesium (Mg++) and potassium (K+) in soils. Other cations
include Al+++( when pH < 5.5) , Na+, and H+.
Cation Exchange Capacity can be expressed two ways:
1. the number of cation adsorption sites per unit weight of soil or,
2. the sum total of exchangeable cations that a soil can adsorb.
Soil CEC is normally expressed in units of charge per weight of
soil. Two different, but numerically equivalent sets of units are
used: meq/100 g (milliequivalents of element per 100 g of dry
soil) or cmolc/kg (centimoles of charge per kilogram of dry
soil).
http://www.swac.umn.edu/classes/soil2125/doc/s12ch2.htm….. Diunduh 27/2/2012
REAKSI PERTUKARAN KATION
BULU AKAR – KOLOID TANAH
http://www.waldeneffect.org/blog/Cation_exchange_capacity/….. Diunduh 27/2/2012