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.
Highlights
Common bean (Phaseolus vulgaris L.) isestimated to be the second most important source of dietary protein and the third most important source of calories (FAOSTAT, 2012)
In the Lake Victoria Crescent agroecological zone, beans are mainly grown on three soil types locally classified as: „Liddugavu‟‟ (Phaoezem, Hapludoll), „„Limyufumyufu‟‟ (Cambisol, Kandiudalf) and „Luyinjayinja‟‟ (Umbrisol, Hapludoll) (Tenywaet al., 2014)
The amount of Ca(OH)2 needed to increase soil pH increases in a nonlinear manner as shown by the quadratic curves that were fit to the data.This nonlinear response to lime applications probably reflects the presence of additional buffering compounds on the soil surfaces that result in smaller increases in pH as higher pH‟s are obtained
Summary
Common bean (Phaseolus vulgaris L.) isestimated to be the second most important source of dietary protein and the third most important source of calories (FAOSTAT, 2012). Uganda‟s bean production is common in the central, eastern and western regions (Sibikoet al., 2013). In the Lake Victoria Crescent agroecological zone, beans are mainly grown on three soil types locally classified as: „Liddugavu‟‟ (Phaoezem, Hapludoll), „„Limyufumyufu‟‟ (Cambisol, Kandiudalf) and „Luyinjayinja‟‟ (Umbrisol, Hapludoll) (Tenywaet al., 2014). The latter two soils are locally known as having the “lunnyo” condition, which according to local, indigenous knowledge suggests multiple factors limit bean (P. vulgaris, L.) production (Fungo et al, 2010)
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