PRESENTED TO THE 1ACCA 18th – 21st MARCH, 2014
LUSAKA
ZAMBIA
Willie C.J. Sagona
Forestry Research Institute of Malawi (FRIM),
Lake Chilwa Basin Climate Change Adaptation Programme
(LCBCCAP)
Presentation Outline
 Introduction
 Historic perspective

Materials and Methods

Results and discussion
Conclusion
Introduction
 The question of providing enough food and better nutrition is a very
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big challenge today (Mongi and Huxley, 1979).
Most poor Malawians make out a living based on unimproved
traditional agricultural production.
95% of the rural population depends on agriculture for both food and
income (Saka, 2002).
Lake Chilwa basin (LCB) is one of the areas that have been
adversely affected by land degradation.
Limiting nitrogen availability and increased soil erosion are some of
the problems.
Introduction of CA in the basin is seen as the most promising
sustainable land use system.
Evaluation of soil physical and chemical characteristics is important
before CA intervention is undertaken.
Historic perspective of soil mgt in
Malawi
 Inorganic fertilizers were introduced to rural primary
schools in the 1950s.
 This time inorganic fertilizers must have been
unknown to smallholder farmers in Malawi.
 The question that arises, naturally, is “How was
farming possible without applying inorganic
fertilizers?”
 Surely the smallholders were making use of the
natural
systems, in one way or another.
 This is reflected by the various strategies they used:
Historic perspective….
 • Strategies
 1. Those based on the natural productivity of the soil.
 - careful selection of sites for gardens.
 Preferred sites
were alluvial plains, sites with dark-coloured soils and
 those supporting natural plants which are associated
 with fertile soils.
 Shifting cultivation whereby a site with productive soils was
opened up for a garden, but it was left for a new site after using it
for a few years.
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2. Those based on adding materials to improve the soil productivity
-applying manures and crop residues to the soil
- rotating legumes and cereal crops
- intercropping legumes and cereal crops
Materials and Methods
SITE:
Methodology:
 Soil samples were collected from
176 fields:
 Phalombe (Kasongo, Mpinda
and Naminjiwa EPA);
 Zomba (Ngwerero EPA); and
 Machinga
(Nsanama and
Nanyumbu EPA).
 Three composite samples were
collected from each field at a
depth of 0 - 10cm, 11- 20cm and
21-30cm.
 Soil samples were analyzed for
physical and chemical properties
using
standard
analysis
procedures
(Anderson
and
Ingram, 1989)
Lab tests and Data analysis
 Laboratory test:
 Texture a and bulk density was analysed using
Hydrometer method

Sodium carbonate and Sodium hexametaphosphate were
used to disperse the soil
 Soil pH was tested using pH meter in Cacl (0.01 mol);
 OM, OC was tested using Walkley – Black method
 in Potassium dichromate and Sulphuric acid reaction;
 Data analysis:
 Microsoft excel package was used for analyzing the
data.
-means and ranges were used to summarize the data.
 Genstat was used to test variation of the results.
Results and Discussion
 Soil physical properties
 7 specific textural classes were observed:
clay, clay loam, loam, loamy sand, sand, sandy clay
loam and sandy loam soils.
 It was observed that LCB is generally dominated by
loam sand soils (39.7%) and sandy soils (27.0%).
 Clay (0.8%) and loam (0.3%) are the least prevalent.
Texture influences the ease with which soil can be
worked, the amount of water and air it holds, and the
rate at which water can enter and move through soil,
organic matter content and pH buffering capacity
(Brady, 1984).
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Bulk Density
 The overall average bulk density was 1.50gcm-3, and it
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ranged from 1.10gcm-3 to 1.60gcm-3.
Bulk density did not vary with depth in all sites observed
under this study.
However, Nanyumbu had the highest overall mean bulk
density (1.60gcm-3) while Ngwelero had least (1.45gcm-3).
Bulk density for loamy sand soils in all sites exceeded the
ideal bulk density (was above 1.40gcm-3).
High bulk density can be attributed to continuous tilling and
turning of the soil under conventional farming methods.
According to Muya et al, (2011), fine textured soils such as silt
and clay have good soil structure and higher pore spaces.
The soils across the sites could generally be said to be of
good bulk density since most soils fall between 1.0 g/cm3 and
2.0 g/cm3
Soil chemical properties
 Soil pH
 The soils in the surveyed sites ranged from slightly acidic
to alkaline with pH ranging from 4.5 – 7.2.
 Mean pH ranged from 5.5 to 6.0.
 Nsanama EPA recorded highest mean pH (6.0) whilst
Ngwelero had the lowest mean pH (5.5).
 Soils fell within the acceptable soil pH range but did not
show any significant difference (P≤0.05) as we dig from 0
to 30cm.
 The effect of soil pH is great on the solubility of minerals
or nutrients.
 Most minerals and nutrients are more soluble or available
in acid soils than in neutral or slightly alkaline soils (Wild,
2003; Sposito, 1989).
Soil organic matter
 SOM content in all sites fell within the
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4
3.5
3
2.5
Kasongo
OM (%)
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normal range for Mw agro-ecozones
(between 2 to 6%), except Ngwelero
=1.2%.
Naminjiwa had the highest mean OM
content (3.32%) while the lowest
mean OM content was recorded in
Ngwelero EPA (1.2%).
Normally, SOM concentration
decreases down the soil profile
(Mongi and Huxley, 1979).
SOM influences the ability of the soil
to hold cations which is measured by
the CEC.
Negatively charged sites of SOM
typically have twice the charge of clay
minerals so even low levels of SOM
can make a significant contribution to
the CEC (Muya et al., 2011).
Mpinda
2
Naminjiwa
Nanyumbu
Nsanama
1.5
Ngwerero
1
0.5
0
10
20
Soil Depth (Cm)
30
Soil Carbon
 Results show that Naminjiwa EPA had the highest mean
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carbon percentage as compared to other sites (1.92%).
This augurs well with the recorded high mean OM (3.32)
of which Carbon is an ingredient.
From the laboratory results, it was also noted that carbon
percentage variation with depth was negligible and did
not show clear pattern.
Normally, carbon is supposed to be more concentrated in
the 0 – 10cm range (Mongi and Huxley, 1979; Brady,
2002).
60 per cent of the carbon in the world’s soils and
vegetation has been lost owing to land use (Houghton,
1995).
Subsequently, in the past years, 1/4 of the global land
area has suffered a decline in productivity and in the
ability to provide ecosystem services because of soil
carbon losses (Bai, et al., 2008).
Linking CA to Fertility Mgt and CC
 It is expected that a review of soil status after some years
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will reveal improvements in the observed physical and
chemical properties.
CA improves soil surface aggregates, reduced compaction
through promotion of biological tillage, increased SOM and
soil carbon content (FAO, 2008).
CA offers locally adapted external inputs that are beneficial
to the most vulnerable farming communities.
CA would also allow farmers to make more use of nutrients
from vegetation and agro-forestry for soil amelioration.
CA is thus considered as a mechanism to manage soil
fertility and adapt to climate change as it increases farmers’
resilience to drought and increases soil water- use efficiency
(FAO, 2008).
Conclusion
 7 specific textural classes were observed, namely clay,
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clay loam, loam, loamy sand, sand, sandy clay loam and
sandy loam soils.
It was established that the basin is generally dominated
by loam sand soils and sand soils with BD for all textural
classes within ideal ranges except for loamy sand soils.
Soils were slightly acidic and SOM content in most sites
was within normal range BUT still low for maximization of
agricultural production.
SOM, carbon and other elements did not show any
pattern of distribution along the profile.
CA has the potential of altering the present soil conditions
in the basin and enhancing famers’ resilience to climate
change.
THE END
THANK YOU!!