Authors: Kalaluka MUNYINDA, Mebelo MATAA, Kephas MPHANDE
An experiment was conducted to determine the effects of increasing soil phosphorus under water stress conditions on yield and plant development in bean (Phaseolus vulgaris L.) genotypes with contrasting drought susceptibility tolerances. A split-split plot design with genotypes (main plot), two water regimes (split plot) and three phosphorus rates (split-split plot) was used. Water regimes were imposed by irrigating at 50% ET (water stress) and 100% ET (no stress). Phosphorus (P2O5) was applied at planting at the following rates- 0, 40 and 70 kg P ha-1. The two bean lines used were Gadra (high drought susceptibility) and KE- 3 (low drought susceptibility). Water stress significantly reduced plant height, shoot biomass, pod length, seeds per pod, pods per plant, days to maturity and grain yield in both genotypes. Phosphorus significantly increased grain yields mainly through increased number of pods per plant and 100-seed weight. Higher increases were observed in Gadra where moderate P application increased yield from about 250 to 1,000 kg ha-1 and high P increased yield to 1,600 kg ha-1. The results suggested that high P foraging and utilisation efficiency were inversely related. Key words: Biomass, soil nutrients, phytotoxicity, yield, yield components.