Exploring options to enhance biological nitrogen fixation and yield of soyabean and common bean in smallholder farming systems in Rwanda

One of my PhD research activities included trials that assessed the effect of mineral fertilizers (N, P, K and their combination) and manure (0, 2 and 5 t ha-1) application on climbing bean yields. This study was carried out in two sites of the Northern Province of Rwanda, which is the major climbing bean growing area in the country. As part of this work, I evaluated the response of mineral fertilizer to manure application, the role of fertilizer and manure on shoot N and P uptake.

Manure application led to a substantial increase in the grain yield with response of fertilizer to manure application ranging from 1.0-1.7 t ha-1 (Table 1). Greater responses were observed in Muko than in Kinoni. On average, greater response of fertilizer to manure addition was achieved when manure was used together with N or NPK fertilizers though there was no significant difference in Kinoni site.

Shoot N and P uptake as affected by inputs application

Shoot N and P uptake were improved by input application and were on average greater in Muko than in Kinoni. In both sites, greater uptake was achieved in plots that received both fertilizer and manure, and were least in plots that had not received any amendment. On average 30 kg P ha-1 and 5 t manure ha-1 applied together increased N uptake from 48.5 to 106.3 kg N ha-1 in Kinoni and from 45.9 to 128.3 kg N ha-1 in Muko. Application of 30 kg P ha-1 and 5 t manure ha-1 also increased P uptake from 6.1 to 12.4 kg P ha-1 in Kinoni and from 5.3 to 17.9 kg P ha-1 in Muko (Table 2). This indicated that there was increased performance of the plant at both sites, hence increased nutrient uptake. Increased N and P uptake in treated plots compared to control plots may be a result of the nutrient supply including N and P, and greater root system development leading to exploitation of a big volume of soil.

Edouard Rurangwa, Wageningen University & Research, The Netherlands, (Click here for his 2016 update)

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