Abstract
AbstractClimbing beans play a central role in food security of rural households in the densely populated highlands of East and Central Africa. Soil fertility degradation and the lack of nutrient inputs are major limitations to yield of beans and other crops. We conducted field trials in Northern Rwanda in Kinoni and Muko villages to evaluate the effect of mineral N, P, and K fertilizers (both alone and in combination) and farmyard manure on nitrogen fixation and grain yields of climbing bean in smallholder farmers’ fields. The trials were laid down in a randomized complete block design with seven replicate blocks in each village. Manure and fertilizer application led to greater yields in all fields, and the largest yields were achieved when manure was combined with NPK. Large variability in yield between fields was observed. Application of fertilizer together with manure increased the grain yield from 1.5 to 3.9 t ha−1in Kinoni and from 2.6 to 5.4 t ha−1in Muko. Fertilizer and/or manure increased stover yield from 0.8 to 2.3 t ha−1in Kinoni and from 1.5 to 3.4 t ha−1in Muko. Application of 30 kg P ha−1and 5 t manure ha−1led to increased N and P uptake (from 49 to 106 kg N ha−1and from 6.1 to 12.4 kg P ha−1in Kinoni and from 46 to 128 kg N ha−1and from 5.3 to 17.9 kg P ha−1in Muko). There was no clear relationship between soil fertility characteristics and the response of climbing bean to applied inputs at Muko site. However, at Kinoni site, limited response to manure and NPK application was observed in plots where soil available P and soil exchangeable K were relatively low. Our results show the benefits of using manure along with mineral fertilizers for increased climbing bean yields and nutrient uptake in smallholder farming systems.
Highlights
In densely populated areas of sub-Saharan Africa, nutrient availability is a major limitation to crop growth, since soil fertility regeneration through fallowing land is no longer possible
The strong effects of manure in increasing crop yields are attributed to its multiple functions such as supply of many nutrients including micronutrients, increasing soil organic matter contents as well as improving soil conditions needed for crop performance (De Ridder and Van Keulen, 1990; Zingore et al, 2008a, 2008b)
The use of manure alongside with mineral fertilizers proved to be beneficial in increasing climbing bean yields
Summary
In densely populated areas of sub-Saharan Africa, nutrient availability is a major limitation to crop growth, since soil fertility regeneration through fallowing land is no longer possible. There is an urgent need to improve agricultural productivity as landholdings have reduced in area due to population growth. To feed the rapidly growing population, sustainable intensification of agricultural production is needed (Vanlauwe et al, 2014), and integrating legumes is key to achieve this goal. Legumes are important crops both for supply of food and fodder and for soil improvement. Legumes fix atmospheric N2 through symbiosis with rhizobia and contribute N to the soil for use by other crops (Franke et al, 2018). The use of legumes in rotation may lead to a reduction in fertilizer-N use, reduced pest and weed occurrence, and improved soil quality (Giller, 2001)
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