Effects of conservation agriculture on soil fertility of smallholder farmers' agricultural filelds in Chafukuma, Solwezi district,Zambia

Abstract

Kansanshi Foundation, a corporate social unit of Kansanshi Mining PLC in Solwezi has been supporting conservation agriculture (CA) among smallholder farmers in Chafukuma area since 2010 without any empirical evidence of CA benefits. This study assessed the effects of CA on soil fertility of agricultural fields in Chafukuma. Paired soil samples were collected from the fields at a depth of 0 - 20 cm. A pair consisted of one sample from a CA managed field that had been cultivated for at least five years and another from a conventional (CV) managed field that had been cultivated for over 20 years that were adjacent. The soil samples were analyzed for any statistically significant differences in available phosphorus (P), exchangeable potassium (K), total nitrogen (N), organic carbon (SOC) and pH levels. Paired sample t-test was used to analyze the soil data with the aid of SPSS Version 20. Field observations were used for recording CA practices employed on the sampled agricultural fields. Perceptions on soil fertility benefits associated with CA were investigated through semi structured interviews. Secondary data on CA were collected through the desk analysis of CA publications. The study showed evidence of CA associated improvements in soil fertility with P 4.80 mg/kg (26.09 mg/kg to 21.29 mg/kg), K 3.23 cmol/kg (11.97 cmol/kg to 8.74 cmol/kg), N 0.73 % (0.96 % to 0.23 %), SOC 1.79 % (3.31 % to 1.52 %) and pH 0.30 (5.49 to 5.19) levels in CA compared to CV managed fields. Statistical analysis showed that the levels of nutrients in CA and CV managed fields were statistically significantly different, with CA managed fields having higher values (Tcalc. ≥ 4.520, p value = 0.0001) than CV fields. This study found that smallholder farmers practiced minimum tillage, crop residue retention and crop rotations in their CA managed fields. These practices were either minimal or absent in CV agricultural managed fields. Farmers’ perceptions were that the practice of CA improved soil fertility in their fields. The results suggest that CA statistically significantly increased the levels of SOC, N, P, K and pH among smallholder farmers’ agricultural fields in Chafukuma. It was concluded that CA improved soil fertility in agricultural fields of smallholder farmers in a high rainfall area, and could be scaled up in smallholder CA systems in other high rainfall areas of Zambia provided all the important agronomic practices are utilized consistently.