Phosphorus efficiency of different varieties of Phaseolus vulgaris L. and sorghum bicolor(L.) moench on an Alfisol in the eastern Ethiopian highlands.
1999
Yohannes Uloro and Richter,C.
P efficiency of two Ethiopian bean varities (Phaseolus vulgaris L., var. Ayenew and Roba 1) and two Sorghum bicolor (L.) Moench varieties (Long Muera and Texax 76) was investigated on an Alfisol in the Hararghe highlands in eastern Ethiopia, where phosphorus (P) deficiency of crops is a serious problem. In pot experiments with a soil low in available P (2 mg CAL-P/100 g), the influence of application of 0.2 g P/3 kg of soil on the plants was tested. A high P efficiency (high yield in spite of P deficiency in the soil) was found for Ayenew compared to Roba 1 and for the Phaseolus compared to the Sorghum varieties. Yield increase (shown by differences in plant height, root length, root and shoot yield) because of P application was less for Ayenew than for Roba 1 and less for beans than for sorghum. But this was not so in P uptake and transport. Reasons for the higher P efficiency of Ayenew compared to Roba 1 were higher values for nodules/plant, nodule diameter, nodule dry weight/plant, p concentration in the nodules per plant and in the nodule dry matter. Furthermore, the P concentration in the dry matter of the seeds diminished in the order Ayenes__Roba 1 __ Long Muera __ Texas 76. As the seed weight decreased in this same order, the corresponding plants had less P reserves, which can be important for the P supply via phloem in the seedling. The root hairs of Ayenew (0.83 mm) were longer than those of Roba 1 (0.45 mm), and those of Roba 1 longer than those of the sorghum varieties, Long Muera (0.23) and Texas 76 (0.28 mm). As a consequence of long root hairs the plants were able to penetrate more soil volume and find more plant available P.
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