Abstract

In East Africa, research has indicated that N, P and soil acidity are the major production constraints to common bean production. The optimum pH for bean production in tropical soils ranges from 5.8 to 6.5. But in Uganda, 23% of beans are grown in soils with pH below 5.0. Research conducted on common bean production is mainly about the major nutrients and information about lime requirements to address soil acidity in different soils is patchy. A study was carried out to determine the lime requirements for Phaseolus vulgaris L. production in Cambisols and Umbrisols and this was based on their low soil pH and Ca levels. The lime requirement was determined using titration method and titration curves for each soil type established by titrating 30 g soil in 60 mL 0.01 M CaCl2 (1:2) with 3 mL 0.022 MCa(OH)2 per addition. Results indicate that to raise pH from 5.02 to 6.5, the Cambisol (“Limyufumyufu”) requires 6.1 tonnes of Ca(OH)2 per hectare, while the Umbrisol(“Luyinjayinja”) requires 5.4 tonnes of Ca(OH)2 per hectare to raise pH from 5.26 to 6.5. There is need to address soil acidity in Cambisol and Umbrisol through liming using the lime requirement equations determined in this study. In order to provide growers and farmers with more options for such acid soils,however, plant breeding programs should select or develop germplasm tolerant to Al toxicity and/ or low soil available phosphorus as well.

Key words: Phaseolus vulgaris L., titration, Al toxicity, Cambisol, Umbrisol.