Soil Nutrient Concentrations and Crop Yields under Sweet Potato (Ipomoea batatas) and Groundnut (Arachis hypogaea) Intercropping in Swaziland

A field experiment was conducted in 2007/2008 cropping season to assess the effects of interplanting a fixed population of groundnut (Arachis hypogaea L.) through a varied population of sweet potato [Ipomoea batatas (L.) Lam.] on soil nutrient concentrations and crop yields. Results showed significant (P < 0.05) differences in the concentrations of potassium (161.5-239.0 mg kg(-1)), nitrate nitrogen (3.0-4.8 mg kg(-1)) and total nitrogen (0.14-0.19%). There were non-significant differences in marketable tuber yields (25.2-28.6 tonnes ha(-1)). There were non-significant differences in groundnut pod yield, though the sole crop yielded higher (2,001.0 kg ha(-1)) than the intercrops (1,382.0-1,366.9 kg ha(-1)). Land equivalent ratio showed greater benefit (LER, 1.67) in the lower sweet potato population of 16,667 plants ha(-1) than in the higher sweet potato population of 33,333 plants ha(-1) (LER, 1.62). It is recommended that small-scale farmers intercrop sweet potato at 16,667 plants ha(-1), with groundnut at 200,000 plants ha(-1).