Abstract

Arid and semi-arid lands (ASALs) are prone to relatively high vegetation and general environmental degradation including soils. Conservation agriculture with trees presents an opportunity to reduce such degradation and enhance soil characteristics-therefore redressing dryland challenges of low productivity- despite its low adoption. The study assessed the soil physical and chemical properties differences for conservation agriculture with trees (CAWT) and conventional tillage from a Kenyan dry land context. We used split plot design arranged in randomized complete block with two farming/tillage systems (conventional and conservation agriculture) as the main blocks, 10 treatments and three replicates. Three multipurpose leguminous shrub species (Calliandra calothyrsus, Cajanas cajan and Gliricidia sepium) were planted in three different spacing at project inception in 2012 (1.5x1 m, 3x1 m, 4.5x1 m) for maize-legume intercrops. Soil samples were taken from 0-30 cm depth and analyzed for selected physical and chemical characteristics. The data was statistically analyzed using ANOVA and means separated using LSD at p <0.05. We find significant moisture increment under conservation agriculture with trees with sole conservation agriculture retaining more moisture than sole conventional agriculture without trees (31.56 and 26.54% vol., respectively, p <0.001). Nitrogen, organic carbon, sodium and potassium are also found to be higher under conservation agriculture. Cation exchange capacity was significantly (p = 0.003) higher (14.372 cmolc/kg) in conventional agriculture than in conservation agriculture (12.718cmolc/kg), and strongly correlated with clay content (r=+0.869). High salinity is also depicted for conventional farming as a result of high Electrical conductivity (CA= 0.541 dS m-1 and COA= 0.063 dS m-1). The results show that conservation farming with integration of trees enhances soil properties in ASAL areas.

Key words: Conservation agriculture, multipurpose shrubs, soil fertility, conventional tillage, agroforestry, climate smart agriculture.