Soil properties after conversion to conservation agriculture from ridge tillage in Southern Malawi

Abstract

A study was carried out to assess some of the likely early impacts on soil properties in small-scale farmers' fields following conversion to conservation agriculture (CA) from annual ridge tillage (RT). Five fields under CA applied for 2 years (CA2 yr) and 5 years (CA5 yr), respectively, were paired with adjacent RT fields with similar soil type and maize genotypes. Soils samples from the 20 fields were taken at depths of 0–10 and 10–20 cm and evaluated for physical and chemical characteristics. The results of analysis of variance and mean comparison showed that soil bulk density and total porosity (PORt) largely remained the same between CA and RT fields. Soil structural stability (SI) was marginally greater under CA practices while RT appeared to sustain better soil aggregation and root-zone aeration characteristics (air capacity, AC). CA5yr fields showed greater values for soil organic carbon (OC), total nitrogen, available phosphorous, and cation exchange capacity (CEC). Volumetric water content at field capacity (θfc) and relative water capacity (RWC) were consistently greater under CA applied for the different number of years. The most influential soil attributes with loadings within ten per cent of those with the highest loadings based on multivariate principal component analysis were θfc,θpwp, θs, upper critical bulk density (ρbU), OC, OC-stock, SI, RWC, AC, θfc/PORt, CEC, and K. Thus, soil attributes found as the most important to discriminate either management system were related to volumetric water content, soil organic carbon fraction, air–water storage, and chemical qualities. These were considered suitable for future assessment of soil quality for monitoring land use change effects in similar agroecosystems. The study posits study of socio-ecology of mulch cover practices to attribute management effects on soil properties.