MK. STELA – smno.jurtnh.fpun.2013
EVALUASI LAHAN UNTUK IRIGASI
Di daerah iklim arid dan semi-arid, di daerah penelitian,
menurut hasil klasifikasi iklim, metode yg paling relevan
untuk memperbaiki produksi pertanian adalah “IRIGASI”.
To decide where and how to irrigate, natural conditions,
available types of crops and technology, previous
experience, costs and benefit analysis, should be
considered.
Untuk meminimumkan dampak negatif akibat praktek
irigasi, seperti erosi tanah dan salinisasi, maka diperlukan
sistem evaluasi untuk tujuan irigasi.
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
LAHAN IRIGASI
Irigasi merupakan upaya yang dilakukan manusia untuk
mengairi lahan pertanian.
Irigasi Permukaan merupakan sistem irigasi yang menyadap
air langsung di sungai melalui bangunan bendung maupun
melalui bangunan pengambilan bebas (free intake)
kemudian air irigasi dialirkan secara gravitasi melalui saluran
sampai ke lahan pertanian.
Dalam hal ini dikenal saluran primer, sekunder, dan tersier.
Pengaturan air ini dilakukan dengan pintu air.
Prosesnya adalah gravitasi, tanah yang tinggi akan
mendapat air lebih dulu.
Sumber: https://id.wikipedia.org/wiki/Irigasi
LAHAN IRIGASI
Di lahan kering, air sangat langka dan pemanfaatannya
harus efisien. Jumlah air irigasi yang diberikan ditetapkan
berdasarkan kebutuhan tanaman, kemampuan tanah
memegang air, serta sarana irigasi yang tersedia.
Ada beberapa sistem irigasi untuk tanah kering, yaitu:
(1) irigasi tetes (drip irrigation),
(2) irigasi curah (sprinkler irrigation),
(3) irigasi saluran terbuka (open ditch irrigation), dan
(4) irigasi bawah permukaan (subsurface irrigation).
Sumber:
LAHAN IRIGASI
Irigasi adalah suatu rekayasa teknik dalam usaha
penyediaan, pengaturan, pemanfaatan, dan
pembuangan air irigasi untuk menunjang
pertanian yang jenisnya meliputi irigasi
permukaan, irigasi rawa, irigasi air bawah tanah,
irigasi pompa dan irigasi tambak.
(PP Irigasi no 20/2006)
Sumber:
LAHAN IRIGASI
Irigasi
adalah usaha penyediaan dan pengaturan air untuk
menunjang pertanian yang jenisnya meliputi
irigasi air permukaan, irigasi air bawah tanah,
irigasi pompa dan irigasi rawa
PP 77/2001
Sumber:
EVALUASI LAHAN UNTUK IRIGASI
Metodologi
Sistem Parametrik digunakan untuk mengevaluasi kesesuaian lahan
bagi penggunaan irigasi (Sys et al., 1991); metode ini didasarkan atas
granulometrical baku dan karakteristik fisika dan kimia tanah.
Evaluasi dilakukan untuk estimasi kesesuaian lahan untuk
irigasi permukaan sekala kecil, sehingga tidak melibatkan
teknik-teknik seperti “drop irrigation”, yang mungkin akan
memberikan hasil evaluais yg berbeda.
Only potential land characteristics were taken into account but
nothing is here reported about effective irrigation possibilities, i.e.
about irrigation water availability.
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
EVALUASI LAHAN UNTUK IRIGASI
Faktor-faktor yg mempengaruhi kesesuaian tanah untuk irigasi
dapat dikelompokkan menjadi empat golongan:
1. Ciri-ciri Fisika tanah, that determine the soil-water
relationship in the soil such as permeability and available water
content (both related to texture, structure, soil depth and
calcium carbonates status);
2. Ciri-ciri Kimia Tanah, that interfere in the
salinity/alkalinity status, such as soluble salts and exchangeable
Na;
3. Ciri-ciri Drainage;
4. Faktor Lingkungan, seperti lereng.
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
During heavy rainfall the
upper soil layers become
saturated and pools may
form.
Water percolates to
deeper layers and
infiltrates from the
pools.
Sumber : http://www.fao.org/docrep/R4082E/r4082e07.htm
SOIL WATER RELATIONS
ABSORPTION OF WATER:
Water in the soil is mostly and abundantly, under normal conditions, is available in
the form of Capillary water. In the soil the space in between soil particle forms a
network of spaces, which normally is filled with water. The water that is present in
such spaces is called capillary water.
Sumber: http://preuniversity.grkraj.org/html/4_PLANT_AND_WATER_RELATIONSHIP.htm
SOIL WATER RELATIONS
Most of the water is
absorbed by the plants
is through root hair
zone.
The figure shows the
pathway of soil water
into root system.
Sumber: http://preuniversity.grkraj.org/html/4_PLANT_AND_WATER_RELATIONSHIP.htm
SOIL WATER RELATIONS
Availability of Water in the Soil
Soil is the major source of water
for plants. The plants absorb water
through root hairs from the soil.
The total water content present in
the soil is called holard. Out of
this, the water which can be
absorbed by plants is chresard and
remaining is called echard.
Diagram Showing Different forms
of Soil Water and their Possible
Relationship with Soil and Plant
Water Status.
Sumber: http://www.tutorvista.com/content/biology/biology-iv/plant-water-relations/availability-water-
SOIL WATER RELATIONS
Jadwal irigasi
Some irrigation water is stored in the soil to be removed by crops and
some is lost by evaporation, runoff, or seepage. The amount of water
lost through these processes is affected by irrigation system design
and irrigation management. Prudent scheduling minimizes runoff and
percolation losses, which in turn usually maximizes irrigation efficiency
by reducing energy and water use. (Of course, in situations where not
enough water was being applied, proper irrigation scheduling will
increase energy and water use.)
When water supplies and irrigation equipment are adequate, irrigators
tend to overirrigate, believing that applying more water will increase
crop yields. Instead, overirrigation can reduce yields because the
excess soil moisture often results in plant disease, nutrient leaching,
and reduced pesticide effectiveness. In addition, water and energy are
wasted.
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-4.html
SOIL WATER RELATIONS
Jadwal irigasi
The quantity of water pumped can often be reduced without
reducing yield. Studies have shown that irrigation scheduling
using water balance methods (to be discussed later) can save 15
to 35 percent of the water normally pumped without reducing
yield. Maximum yield usually does not equate to maximum
profit.
The optimum economic yield is less than the maximum potential yield.
Irrigation scheduling tips presented in popular farm magazines too
often aim at achieving maximum yield with too little emphasis on
water and energy use effficiencies.
An optimum irrigation schedule maximizes profit and optimizes water
and energy use.
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-4.html
SOIL WATER RELATIONS
MENGHUBUNGKAN AIR-TANAH DENGAN CEKAMAN TANAMAN
Jumlah air yg harus diberikan pada setiap aktivitas irigasi tergantung pada
sifat tanah dan jumlah air-tersedia yang dapat disimpan dalam tanah.
Jumlah air-tanah yg diserap tanaman sejak irigasi atau hujan terakhir
disebut sebagai “depletion volume”.
Irrigation should begin when the crop comes under water stress severe
enough to reduce crop yield or quality. The level of stress that will cause a
reduction in crop yield or quality depends on the kind of crop and its stage of
development; the level varies during the growing season as the crop
matures. For example, corn will tolerate more stress without causing a yield
reduction when the stress occurs during the vegetative stage as opposed to
the pollination stage. Thus, determining when to irrigate is a scheduling
decision that should take into account the crop's sensitivity to stress.
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-4.html
SOIL WATER RELATIONS
The relationship between water distribution in the soil and the concept of irrigation
scheduling when 50 percent of the PAW has been depleted.
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-4.html
SOIL WATER RELATIONS
Determining When to Irrigate
There are three ways to decide when to
irrigate:
1. measure soil-water
2. estimate soil-water using an accounting
approach (the check-book method)
3. measure crop stress.
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-4.html
SOIL WATER RELATIONS
Irrigation scheduling is simply knowing when to irrigate and
how much irrigatzon water to apply. An effective irrigation
schedule helps to maximize profit while minimizing water
and energy use.
The following factors contribute to developing a workable
and efficient irrigation schedule:
1. soil properties
2. soil-water relationships
3. type of crop and its sensitivity to drought stress
4. stage of crop development
5. availability of a water supply
6. climatic factors such as rainfall and temperature.
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-1.html
SOIL WATER RELATIONS
Relationship between plant-available water and water distribution in the soil.
Plant-available water, PAW, is the volume of water stored in the soil reservoir that can
be used by plants. It is the difference between the volume of water stored when the
soil is at field capacity and the volume still remaining when the soil reaches the
permanent wilting point (the lower limit)
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-1.html
SOIL WATER RELATIONS
Most crops will recover overnight from temporary wilting if less than
50 percent of the PAW has been depleted. Therefore, the allowable
depletion volume generally recommended in North Carolina is 50
percent (Figure 9). However, the recommended volume may range
from 40 percent or less in sandy soils to greater than 60 percent in
clayey soils.
The allowable depletion is also dependent on the type of crop, its
stage of development, and its sensitivity to drought stress. For
example, the allowable depletion recommended for some droughtsensitive crops (vegetable crops in particular) is only 20 percent during
critical stages of development.
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-1.html
SOIL WATER RELATIONS
The relationship between water distribution in the soil and the
concept of irrigation scheduling when 50 percent of the PAW has been
depleted.
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-1.html
SOIL WATER RELATIONS
. Effective Root Depth
Rooting depth is the depth of the soil reservoir that the plant can reach to get PAW.
Crop roots do not extract water uniformly from the entire root zone. Thus,the
effective root depth is that portion of the root zone where the crop extracts the
majority of its water. Effective root depth is determined by both crop and soil
properties.Plant Influence on Effective Root Depth. Different species of plants have
different potential rooting depths. The potential rooting depth is the maximum
rooting depth of a crop when grown in a moist soil with no barriers or restrictions
that inhibit root elongation. Potential rooting depths of most agricultural crops
important in North Carolina range from about 2 to 5 feet. For example, the potential
rooting depth of corn is about 4 feet.
Water uptake by a specific crop is closely related to its root distribution in the soil.
About 70 percent of a plant's roots are found in the upper half of the crop's
maximum rooting depth. Deeper roots can extract moisture to keep the plant alive,
but they do not extract suffficient water to maintain optimum growth. When
adequate moisture is present, water uptake by the crop is about the same as its root
distribution. Thus, about 70 percent of the water used by the crop comes from the
upper half of the root zone (Figure 10). This zone is the effective root depth.
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-1.html
SOIL WATER RELATIONS
The amount of water extracted by plants is influenced by the
distribution of the root in the soil.
Sumber: http://www.bae.ncsu.edu/programs/extension/evans/ag452-1.html
SOIL WATER RELATIONS
. Root zone soil water extraction and plant root development patterns.
Sumber: http://www.ianrpubs.unl.edu/pages/publicationD.jsp?publicationId=1004
SOIL PERMEABILITY
Permeabilitas tanah merupakan sifat tanah untuk dapat
merembeskan air dan udara , dan sifat ini sangat penting
dalam kaitannya dengan IRRIGATION.
Banyak faktor mempengaruhi permeabilitas tanah. Sometimes
they are extremely localized, such as cracks and holes, and it is
difficult to calculate representative values of permeability from
actual measurements.
Observations on soil texture, structure, consistency,
colour/mottling, layering, visible pores and depth to
impermeable layers such as bedrock and claypan* form the basis
for deciding if permeability measurements are likely to be
representative.
Sumber: ftp://ftp.fao.org/fi/CDrom/FAO_Training/FAO_Training/General/x6706e/x6706e09.htm
SOIL PERMEABILITY
Soil permeability relates to soil texture and structure
The size of the soil pores is of great importance with
regard to the rate of infiltration (movement of water
into the soil) and to the rate of percolation
(movement of water through the soil).
Pore size and the number of pores closely relate to
soil texture and structure, and also influence soil
permeability.
Sumber: ftp://ftp.fao.org/fi/CDrom/FAO_Training/FAO_Training/General/x6706e/x6706e09.htm
SOIL PERMEABILITY
Rataan permeabilitas berbagai tekstur tanah
(cm/hour )
PASIR = Sand
5.0
Sandy loam
2.5
Loam
1.3
Clay loam
0.8
Silty clay
0.25
LIAT = Clay
0.05
Sumber: ftp://ftp.fao.org/fi/CDrom/FAO_Training/FAO_Training/General/x6706e/x6706e09.htm
SOIL PERMEABILITY
Struktur tanah sangat ememodifikasi laju permeabilitas:
Tipe Struktur Tanah
Permeability1
- Greatly
overlapping
Platy
- Slightly
overlapping
Dari sangat lambat
menjadi sangat cepat
Blocky
Prismatic
Granular
Sumber: ftp://ftp.fao.org/fi/CDrom/FAO_Training/FAO_Training/General/x6706e/x6706e09.htm
SOIL PERMEABILITY
Soil permeability classes
Permeability is commonly
measured in terms of the
rate of water flow through
the soil in a given period of
time. It is usually expressed
either as a permeability rate
in centimetres per hour
(cm/h), millimetres per hour
(mm/h), or centimetres per
day (cm/d), or as a
coefficient of permeability k
in metres per second (m/s)
or in centimetres per second
(cm/s).
Sumber: ftp://ftp.fao.org/fi/CDrom/FAO_Training/FAO_Training/General/x6706e/x6706e09.htm
SOIL PERMEABILITY
Kelas Permeabilitas Tanah untuk Pertanian dan Konservasi
Kelas Permeabilitas Tanah
Laju Permeabilitas1
cm/hour
cm/day
Less than 0.13
Less than 3
Slow
0.13 - 0.3
3 - 12
Moderately slow
0.5 - 2.0
12 - 48
Moderate
2.0 - 6.3
48 - 151
Moderately rapid
6.3 - 12.7
151 - 305
Rapid
12.7 - 25
305 - 600
More than 25
More than 600
Sangat Lambat - Very slow
SANGAT CEPAT - Very rapid
Sumber: ftp://ftp.fao.org/fi/CDrom/FAO_Training/FAO_Training/General/x6706e/x6706e09.htm
SOIL PERMEABILITY
Permeability also varies with soil texture and structure. Permeability is
generally rated from very rapid to very slow. This is the mechanism by
which water reaches the subsoil and rooting zone of plants. It also
refers to the movement of water below the root zone. Water that
percolates deep in the soil may reach a perched water table or
groundwater aquifer.
Sumber:
SOIL PERMEABILITY
Infiltration and permeability describe the manner by which
water moves into and through soil. Water held in a soil is
described by the term water content. Water content can be
quantified on both a gravimetric (g water/g soil) and
volumetric (ml water/ml soil) basis.
The volumetric expression of water content is used most
often. Since 1 gram of water is equal to 1 milliliter of water,
we can easily determine the weight of water and
immediately know its volume.
The following discussion will consider water content on a
volumetric basis.
Sumber: http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447039&topicorder=10&maxto=10
SOIL PERMEABILITY
Water holding capacity designates the ability of a soil to hold water. It
is useful information for irrigation scheduling, crop selection,
groundwater contamination considerations, estimating runoff and
determining when plants will become stressed. Water holding capacity
varies by soil texture .
Sumber: http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447039&topicorder=10&maxto=10
SOIL WHC
Medium textured soils (fine sandy loam, silt loam and silty
clay loam) have the highest water holding capacity,
while coarse soils (sand, loamy sand and sandy loam) have
the lowest water holding capacity. Medium textured soils
with a blend of silt, clay and sand particles and good
aggregation provide a large number of pores that hold water
against gravity.
Coarse soils are dominated by sand and have very little silt
and clay. Because of this, there is little aggregation and few
small pores that will hold water against gravity. Fine
textured clayey soils have a lot of small pores that hold
much water against gravity. Water is held very tightly in the
small pores making it difficult for plants to adsorb it.
Sumber: http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447039&topicorder=10&maxto=10
SOIL PERMEABILITY
Since soil texture varies by depth, so does water holding capacity. A soil may have a
clayey surface with a silty B horizon and a sandy C horizon. To determine water
holding capacity for the soil profile, the depth of each horizon is multiplied by the
available water for that soil texture, and then the values for the different horizons
are added together.
Calculation of water holding capacity for a soil profile:
Sumber: http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447039&topicorder=10&maxto=10
SOIL DRAINAGE
Well-drained soils also are preferred for many nonagricultural uses.
Home sites and housing developments should be located in welldrained soils, especially if basements are to remain dry and septic
systems are to function efficiently.
One of the best indicators of drainage class is soil color. The more
redoximorphic features (mottling due to wetness) and gray in the
subsoil, the poorer the soil drainage, the longer and higher the water
tables stand in a soil profile, the more intense is the mottling and the
higher it occurs within the profile. Soil scientists recognize six drainage
classes in the field. Figure 23 shows the relationship
between topography or position on the landscape and the
resulting soil drainage. The water table, as indicated on the figure, is
shown as it might appear during wet seasons.
Sumber: http://faculty.msmary.edu/envirothon/current/guide/soil_structure.htm
Kelas drainage dan lokasinya pada landskap
Maryland.
Sumber: http://faculty.msmary.edu/envirothon/current/guide/soil_structure.htm
SOIL DRAINAGE
DRAINAGE BERLEBIHAN
Water is removed from the soil very rapidly because of
either coarse textures (such as sand and loamy sand) or
shallow, porous profiles on steep slopes. Excessively drained
soils are suited poorly to agriculture unless irrigation is
practiced. No drainage mottles occur in these soils.
DRAINAGE BAIK.
Aerasi tanahnya bagus. Subsoil colors are bright and the
profile lacks redoximorphic features above 1 m (40
in.). Brown, yellowish brown and reddish brown colors
are common.
Sumber: http://faculty.msmary.edu/envirothon/current/guide/soil_structure.htm
SOIL DRAINAGE
DRAINAGE CUKUP BAIK
In these soils, redoximorphic features are present above 1 m
(40 in.) indicating that saturated conditions or water tables
occur above this depth at various times during the year.
Mottles are restricted to the 0.5 to 1 m (20 to 40 in.) zone
for classification in this category. These soils may retard crop
growth in wet years, but crops may do very well during
drought periods.
Artificial drainage may be beneficial during wet periods.
Septic systems may experience periodic failure during
saturated conditions.
Sumber: http://faculty.msmary.edu/envirothon/current/guide/soil_structure.htm
SOIL DRAINAGE
DRAINAGE AGAK BURUK
Redoximorphic features occur within the 10 to 20 in. zone,
indicating prolonged periods of saturation or high water
tables.
Gangguan atau kegagalan tanaman yg serus dapat terjadi
selama tahun-tahun basah. Kalau ridak ada drainage
buatan, produksi tanaman terhambat dan sistem septik
biasanya gagal.
Sumber: http://faculty.msmary.edu/envirothon/current/guide/soil_structure.htm
SOIL DRAINAGE
Poorly drained.
These soils have dark surface horizons and gray
subsoils with redoximorphic features occurring
above 25 cm (10 in.).
They have high water tables or are ponded for long
periods or both. These soils usually occupy
level areas or footslope positions and are productive
only if they are artificially drained. Development of
these soils for home sites should be avoided.
Sumber: http://faculty.msmary.edu/envirothon/current/guide/soil_structure.htm
SOIL DRAINAGE
DRAINAGE SANGAT BURUK
Water is removed so slowly that the water table remains at
or on the surface much of the year. These soils usually
occupy low-lying and concave or depressed positions on the
landscape.
They normally have very dark or black, thick surface
horizons with relatively high organic matter contents. The
subsoils usually are gray. These soils can be used for
agriculture, but only if intensive drainage is practiced.
Sumber: http://faculty.msmary.edu/envirothon/current/guide/soil_structure.htm
SOIL DRAINAGE
The soil drainage class and some characteristic features
associated with each class are depicted in the following
figure (from Soil Survey).
One characteristic feature in the figure is the depth of
rooting that typically occurs in each drainage class, providing
there are no other restrictions (i.e., compacted layer) to root
penetration.
Deeper rooting depths are associated with well drained
soils, because the depth of the water table below the
surface is not restricting root growth and oxygen exchange.
Sumber: http://nrcca.cals.cornell.edu/soil/CA3/
SOIL DRAINAGE
Although not all plant species respond the same, for most common agricultural
crops, a deeper and healthy root environment translates into higher biomass
productivity. Studies in New York have shown 2 to 3 fold yield increases in corn and
forage production on well drained soils as compared to those grown on somewhat
poorly to poorly drained soils.
Sumber: http://nrcca.cals.cornell.edu/soil/CA3/
LAHAN IRIGASI
Sumber:
EVALUASI LAHAN UNTUK IRIGASI
The different land characteristics that influence the soil suitability for
irrigation are rated and a capability index for irrigation (Ci) is
calculated according to the formula:
Ci = A/100 * B/100 * C/100 * D/100 * E/100 * F/100
dimana:
Ci: Indeks kapabilitas untuk irigasi; A: nilai tekstur tanah; B:
nilai kedalaman tanah; C: nilai status CaCO3 ;
D: nilai salinitas/alkalinitas; E: nilai drainage dan F: nilai
slope.
Kelas kapabilitas didefinisikan menurut nilai indeks
kapabilitasnya (atau kesesuaian) (Ci) (Table 28).
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
EVALUASI LAHAN UNTUK IRIGASI
Table 28 - Capability indexes for the different capability classes
Indeks
Kapabilitas
Class
Definition
Symbol
>80
I
Excellent
S1
60-80
II
Suitable
S2
45-60
III
Slightly suitable
S3
30-45
IV
Almost unsuitable
N1
<30
V
Unsuitable
N2
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
EVALUASI LAHAN UNTUK IRIGASI
For slope class, texture, soil depth, calcium
carbonate status, salinity and alkalinity,
drainage, a weighted average was calculated
for the upper 100cm of the soil profile then
the considered factors were rated according
to Table 29-Table 34.
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
EVALUASI LAHAN UNTUK IRIGASI
Table 29 - Rating of slopes (after Sys et al., 1991)
Slope class (%)
0-1
1-3
3-5
5-8
8-16
16-30
>30
Rating
Non terraced Terraced
100
100
95
95
90
95
80
95
60
85
50
70
30
50
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
EVALUASI LAHAN UNTUK IRIGASI
Table 30 - Rating of textural classes for irrigation (after Sys et al., 1991)
KELAS TEKSTUR TANAH
Clay – LIAT
Loam – LEMPUNG
Sand – PASIR
Silt – DEBU
Sandy clay loam
Silty clay loam
Loamy sand – PASIR BERLEMPUNG
Sandy clay – LIAT BERPASIR
Silty clay – LIAT BERDEBU
Clay loam – LEMPUNG LIAT
Sandy clay – LIAT BERPASIR
Silt loam – LEMPUNG DEBU
<15%
Gravel
65
90
30
90
95
100
55
75
85
100
80
90
Rating
15-40%
Gravel
65
80
25
80
85
90
50
65
95
90
90
80
40-75%
Gravel
55
70
25
70
75
80
45
60
80
80
75
70
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
EVALUASI LAHAN UNTUK IRIGASI
Table 31 - Rating of soil depth (after Sys et al., 1991)
Table 32 - Rating of CaCO3 (Sys et al., 1991)
Soil depth (cm)
Rating
CaCO3 (%)
Rating
<20
30
>50
30
20-50
60
25-50
60
50-80
80
10-25
85
80-100
>100
90
100
0.3-10
100
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
Table 33 - Rating of salinity and alkalinity (after Sys et al., 1991)
Electric conductivity (mS)
Na+ (%)
0-4
4-8
8-16
16-30
>30
0-8
100
100*
95
90*
90
80*
85
70*
80
60*
8-15
95
90*
90
80*
85
70*
80
60*
75
50*
15-30
90
80*
85
70*
80
60*
75
50*
70
40*
>30
85
70*
80
60*
75
50*
70
40*
65
30*
(*) Clay, Silty clay, and Sandy clay
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
Table 34 - Rating of drainage classes (after Sys et al., 1991, modified)Results and
discussion
Rating
Kelas Drainage
Clay, silty clay, sandy clay, silty other
clay loam
textures
Excessively drained
100
100
Somewhat excessively drained
80
100
Well drained
85
95
Moderately drained
65
80
Somewhat poorly drained
55
70
Poorly drained
45
Very poorly drained
30
55
50
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
EVALUASI LAHAN UNTUK IRIGASI
Figure 24 - Land suitability for irrigation
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
EVALUASI LAHAN UNTUK IRIGASI
Table 35 - Absolute and relative extent of different classes of
suitability for irrigation
Class
Land unit
S2
Area
10, 12, 22, 23, 6, 31
km2
42,65
%
6,59
S3
1, 8, 9, 11, 13, 14, 18, 34
229,73
35,51
N1
7, 4, 17, 19, 20, 21, 25, 26, 27, 28, 29, 32,
35, 37, 33
157,55
24,35
N2
2, 3, 5, 15, 16, 24, 30, 36
168,40
26,03
Not Relevant
U, R, Q
12,04
1,86
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
EVALUASI LAHAN UNTUK IRIGASI
Di lokasi penelitian tidak ada area yg sangat sesuai untuk irigasi.
Moderately suitable land units are located in the alluvial valley
(western part of the study area), and in the forest of Ben Slimane,
where, of course, irrigation transformation is purely theoretical.
The largest part of the agricultural areas were classified as marginally
suitable, the most limiting factors being physical parameters such as
slope, soil texture, and soil depth.
This does not exclude the presence of small favoured areas where
conditions can be much better.
Faktor kimiawi seperti salinitas dan kandungan CaCO3 umumnya
bukan faktor pembatas di lokasi penelitian.
Sumber: http://www.iao.florence.it/training/geomatics/BenSlimane/Marocco21_4_2_3.htm
EVALUASI LAHAN UNTUK IRIGASI
Pada lokasi dataran, banyak area yang tidak sesuai karena faktor
pembatas sifat fisika tanah :
Faktor pembatas tidak dapat diatasi dengan tingkat
pengelolaan yanag ada sekarang, tetapi masih
dimungkinkan untuk irigasi dengan menerapkan teknikteknik mirigasi lainnya.
In fact, some scattered spots of trees and vegetable orchards with
drop irrigation are occasionally present, demonstrating the feasibility
of these techniques.
In the eastern escarpments, steep slopes and shallow soils lead to
permanent unsuitable conditions for surface irrigation.
STELA – smno-fpub-mei2013