Performance of Cassava under Lime, Fertilizer, and Legume Intercropping on Exhausted Land in Northern Zambia

Abstract

Cassava yields of 6 t ha−1 are lower than the potential yield of 20–25 t ha−1 obtained in Northern Zambia. It is grown in legume intercropping with little or no fertilizer, causing nutrient depletion with consequent land abandonment. Therefore, the study objective was to investigate the performance of cassava under lime, fertilizer, and grain legume intercropping on exhausted land in Northern Zambia. A split-split plot design experiment was conducted over two seasons, comprising two lime rates (0 and 300 kg ha−1), two fertilizer rates (0 and 100N : 23P:80 K kg ha−1), and three grain legumes (common beans, cowpea, and soybean) intercropped in cassava and sole cassava arranged in RCBD with three replications. Periodic measurements of leaf area index (LAI), light interception, weather data, and yield components were recorded. A linear mixed model with year as a random factor was performed to assess the treatment effect of lime, fertilizer, and legume species intercropping on cassava growth characteristics, radiation-use efficiency (RUE), and selected yield components. Lime, fertilizer rates, and legume species intercropping were assigned as main, sub-, and sub-sub-treatments, respectively. Fertilization and fertilization + lime treatments in sole cassava and cassava-common bean intercropping significantly increased the RUE and light extinction coefficient (k) compared to nonfertilized and only lime treatments. Lime x fertilizer x cropping system interaction was significant on chlorophyll index and plant height, RUE, tuber yield, HI, and total dry matter (TDM) yield. Cropping system x year interactions were significant on season LAI. On average, every kg of cassava yield loss in intercropping was compensated by 0.46 kg soybean, 0.20 kg common beans, and 0.26 kg of cowpea. NPK fertilizer + lime, NPK fertilizer, and grain legume intercropping may be adopted to increase cassava tuber yields and legume grain yield response on nutrient-depleted soils in high rainfall areas of Zambia.