Fertilizer, Lime and intercropping effects on acid soil, sorrel weed Rumex acetosella L. growth and perfomance of potato solanum tubersum L. in Molo, Kenya

Abstract

Soil fertility decline and soil acidity in potato (Solanum zuberosum L.) producing areas of Kenya have resulted in reduced tuber yields and sheep sorrel (Rumex acetosella) weed infestation. A two-season field experiment was set up in an acid mollic Andosol of Molo sub- county, Kenya. The objectives were to investigate (i) the effects of liming, intercropping and NPK fertilizer application on selected properties, (ii) the effects of liming, intercropping and NPK fenilizer application on sheep sorrel weed growth and (m) the effects of liming, intercropping and NPK fertilizer application on potato growth, nutrient uptake and yield. A randomized complete block design with a split-split plot arrangement, replicated three times, was used. The compound Fertilizer NPK at two levels (0 and 0.2 t ha -1), formed the main plots. Lime rates (0 and 2 t ha '1) were assigned to the sub-plots and cropping system (sole potato and potato/dolichos intercrop) the sub-sub plots. Potato Shangi variety and dolichos hyacinth bean variety were used. Lime was applied 3 weeks before planting. The results showed that application of lime increased the soil pH by 5% while fertilizer application reduced soil pH by 2% over the control. Combined application of NPK fertilizer and lime increased available soil P up to 3l.08ppm. Total soil N increased to between 0.26 and 0.28% where fertilizer was applied in potato cropping system across the seasons. The interaction between NPK fertilizer and lime potato/dolichos cropping system, reduced the sheep sorrel weed density, dry biomass and root length by 43%, 32% and 39% during the second season respectively. Higher plant height 74 and 77cm were obtained where fertilizer was applied and in the second season respectively. More shoots, 5, were observed in the second season. Season X fertilizer and fertilizer X lime interactions increased N uptake up to 140.73 and l46.77kg ha'l, respectively, in potato/ dolichos intercropping system. Lime X cropping system and lime X fertilizer interactions increased P uptake up to 22.16 and 27.l9kg had during the second season respectively. More tubers (1 1) per plant were obtained in cropping system X fertilizer, cropping system X season and fertilizer X season interactions. Higher tuber yields, 50,51 and 53t ha'1 were realized in cropping system X season X fertilizer, cropping system X season X lime and lime X fertilizer X season interactions respectively. The study therefore recommends application of 0.2 t ha] NPK fertilizer and 2 t ha'1 lime, and dolichos integration in potato systems for soil acidity amelioration, improving soil nutrient status, reducing sorrel weed infestation, and increasing potato nutrient uptake, growth and yield