Abstract
Farmers in Northern Ethiopia integrate legumes in their cropping systems to improve soil fertility. However, biological nitrogen fixation (BNF) potentials of different legumes and their mineral nitrogen (N) and phosphorus (P) demands for optimum BNF and yields are less studied. This study aimed to generate the necessary knowledge to enable development of informed nutrient management recommendations, guide governmental public policy and assist farmer decision making. The experiment was conducted at farmers’ fields with four N levels, three P levels, and three replications. Nodule number and dry biomass per plant were assessed. Nitrogen difference method was used to estimate the amount of fixed N by assuming legume BNF was responsible for differences in plant N and soil mineral N measured between legume treatments and wheat. The result revealed that the highest grain yields of faba bean (2531 kg ha−1), field pea (2493 kg ha−1) and dekeko (1694 kg ha−1) were recorded with the combined application of 20 kg N ha−1 and 20 kg P ha−1. Faba bean, field pea and dekeko also fixed 97, 38 and 49 kg N ha−1, respectively, with the combined application of 20 kg N ha−1 and 20 kg P ha−1; however, lentil fixed 20 kg ha−1 with the combined application of 10 kg N ha−1 and 10 kg P ha−1. The average BNF of legumes in the average of all N and P interaction rates were 67, 23, 32 and 16 kg N ha−1 for faba bean, field pea, dekeko and lentil, respectively. Moreover, faba bean, field pea, dekeko and lentil accumulated a surplus soil N of 37, 21, 26 and 13 kg ha−1, respectively, over the wheat plot. The application of 20 kg N ha−1 and 20 kg P ha−1 levels alone and combined significantly (p < 0.05) increased the nodulation, BNF and yield of legumes; however, 46 kg N ha-1 significantly decreased BNF. This indicated that the combination of 20 kg N ha−1 and 20 kg P ha−1 levels is what mineral fertilizer demands to optimize the BNF and yield of legumes. The results of this study can lead to the development of policy and farmer guidelines, as intensification of the use of legumes supplied with starter N and P fertilizers in Northern Ethiopian cropping systems has the multiple benefits of enhancing inputs of fixed N, improving the soil N status for following crops, and becoming a sustainable option for sustainable soil fertility management practice.
Highlights
The global concern regarding food demand for the increasing human population has been strengthening the importance of sustainable agricultural production [1]
The sole application of 20 kg N ha−1 has increased the yield of faba bean, field pea, dekeko and lentil by 304, 222, 231 and 100 kg ha−1, respectively, over the plot with nil nutrient supply
The interaction of different N and P rates significantly (p < 0.05) affected the dry biomass and grain yield of faba bean, field pea and dekeko, which were highest in the interaction of 20 kg N ha−1 and 20 kg P ha−1 (Table 1)
Summary
The global concern regarding food demand for the increasing human population has been strengthening the importance of sustainable agricultural production [1]. Smallholder farmers practicing rain-fed agriculture in sub-Saharan Africa (SSA) including Ethiopia, face food insecurity due to poor soil fertility and climate change [2]. Soil fertility management is critical to improve sustainable agricultural production and food security in Ethiopia [3,4,5,6,7]. The government of Ethiopia has made tremendous effort to improve soil fertility and increase agricultural productivity [9]. Due to high cost of the inorganic fertilizers, it is rare for poor farmers to use mineral fertilizers; as a result, crop yield is declining. Soil fertility management practices, which are accessible for resource poor farmers like BNF and sustainably improve agricultural productivity, are essential
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
