Abstract
Agricultural activities that encourage slashing, burning and ploughing greatly affect the soil structure and soil organic matter on which soil water retention depends. In this study, we hypothesized that inclusion of rotational leguminous tree species improves soil water retention in a semi-arid conservation agriculture system. In a study done in Kibwezi, semi-arid eastern Kenya, results showed that the amount of water retained in the different soil strata from plots with different tree species and tillage practices was highly significant (P = 0.032). Plots with planting basins and Gliricidia sepium and Faidherbia albida tree species retained more water in both the upper and lower strata. Plots with G. sepium tree species under planting basins and zero tillage under F. albida had significantly higher soil organic carbon levels than plots that were managed under ridges and ploughing (P = 0.002). On the other hand, bulk density in plots with planting basins and zero tillage and ridges ranged between 1.35 g/cm3 and 1.53 g/cm3. Conventional tillage plots had bulk density values of 1.65 g/cm3 and 1.72 g/cm3 in the upper and lower strata respectively. The time-dependent nature of rotational leguminous tree species on soil organic matter and soil water retention in the semi-arid conservation agriculture system highlights the importance of considering these species for improving organic carbon and water retention for improved crop production.
Highlights
Soil and water losses are becoming a major challenge to smallholder farmers
Smallholder farming areas in semi-arid regions are low in soil organic matter and this makes the soil to have low soil structural stability, soil fertility and hydraulic properties (Lal, 2002) leading to water losses through runoff and reduction in the amount of water that infiltrates into the soil (Rao et al, 1998)
Some of these practices lead to the break down in soil organic carbon and destruction of the soil structure resulting in increased runoff and soil and water losses (Nyamadzawo et al, 2008; Thierfelder & Wall, 2009)
Summary
Soil and water losses are becoming a major challenge to smallholder farmers. Declining crop yields and increasing levels of food insecurity especially among the smallholder farmers in the arid and semi-arid regions have been blamed on increased soil and water losses (Hernanz et al, 2002). Chivenge et al (2007) point out that tillage plays a significant part in influencing nutrient storage and release from soil organic matter. Some of these practices lead to the break down in soil organic carbon and destruction of the soil structure resulting in increased runoff and soil and water losses (Nyamadzawo et al, 2008; Thierfelder & Wall, 2009). Soil organic matter represents a major proportion of the organic carbon within the terrestrial biosphere which plays an important role in soil fertility (Powlson et al, 2001) and affects infiltration, water retention, crop growth and productivity (Cattanio, 2012; Imogie et al, 2008). In view of the foregoing, it is important that higher rain use efficiency be achieved so that the infiltration rate of the soil is increased to diminish losses of water through runoff (Gicheru et al, 2004)
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