PRESENTED TO THE 1ACCA 18th – 21 st 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 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. 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

SITE:

Materials and Methods

Methodology:

 Soil samples were collected from 176 fields:  Phalombe (Kasongo, Mpinda and Naminjiwa EPA);     Zomba (Ngwerero EPA); and Machinga (Nsanama Nanyumbu EPA).

and 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 procedures standard (Anderson analysis 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).

Bulk Density

       The overall average bulk density was 1.50gcm

-3 , and it 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/cm 3 and 2.0 g/cm 3

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 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).

4 3,5 3 2,5 2 1,5 1 0,5 0 10 20

Soil Depth (Cm)

30 Kasongo Mpinda Naminjiwa Nanyumbu Nsanama Ngwerero

Soil Carbon

 Results show that Naminjiwa EPA had the highest mean 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 vegetation has been lost owing to land use (Houghton, 1995).

world’s soils and  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

  CA improves soil surface aggregates, reduced compaction through promotion of biological tillage, increased SOM and soil carbon content (FAO, 2008).  It is expected that a review of soil status after some years will reveal improvements in the observed physical and chemical properties. 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

  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.

 7 specific textural classes were observed, namely clay, clay loam, loam, loamy sand, sand, sandy clay loam and sandy loam 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!!