Responses of Nodulation and Grain Yield to Fertilization with Phosphorus (P) of Outstanding Low P Tolerant Phaseolus vulgaris L. Genotypes in Highly Acidic and Phosphorus Deficient Soils Such of Rwanda
J. Gatesi *
University of Rwanda, Rwanda.
O. Nsanzimana *
University of Rwanda, Rwanda.
*Author to whom correspondence should be addressed.
Abstract
Promoting the use of low phosphorus (P) and acidity tolerant bean genotypes in highly acidic and low P soils is a long term cost-effective strategy to increase bean production in sub-Saharan countries. Moreover, the performance of beans under the widespread soil related stresses like acidic and P deficient is not well documented. Thus, pot experiments were established in greenhouses in Rubona, Rwanda. Each pot was filled with 5 kg of highly acidic and P deficient soil collected from Nyamagabe district. The objective of the experiment was to identify superior grain yielding and nodulating bean genotypes suitable for such acidic and P deficient soils and their response to P inputs. Four low P tolerant genotypes used (G 2858, RWR 1873, RWV 1668; and RWV 1348) and 59/1-2 (local check) were subjected to three levels of P (0, 5, 10 mg kg-1) and treatments were laid in completely randomized design with 6 replications. The climbing genotype RWV 1348 had the highest grain yield (22.9 g pot-1), followed by two bush genotypes RWR 1873 and RWV 1668 with the same grain yield of 14.7 g pot-1, while the local check (climbing) and GR 2548 (climbing) had low grain yield. Nodulation efficiency was 73, 54, 50% for RWR 1873, RWV 1348 and RWV 1668 respectively. Again, the local check and GR2548 had low effective nodulation (19 and 31% respectively). The input of P at 5 mg kg-1 soil increased grain yield of RWV 1348, RWR 1873 and RWV 1668 at 17, 21, and 33% respectively. On the other hand, doubling this rate has declined the yield of all genotypes. Genotype RWV 1348, a climber, is the best outstanding low P tolerant bean genotype under the highly acidic and low P deficient soils such of Rwanda and have a slight grain yield response when P fertilizer is applied. The two-bush bean genotype RWV 1873 and RWV 1688 are also outstanding low P tolerant bean genotypes compared to a climbing local check (59/1-2) and other low P tolerant climber (G2858). The genotypes RWV 1873 and RWV 1688 grain yield response to P fertilizer application has the same pattern as of RWV 1348. They are all outstanding low P tolerant genotypes and their nodulation efficiency is not responsive at P fertilizer application.
Keywords: Acidic and phosphorus deficient soils, nodulation response, low phosphorus tolerant bean genotypes, yield