Increasing land pressure and soil degradation, together with the limited availability of fertilizers, labour, equipment and technology, keeps production efficiency low for smallholder farmers. Maize (Zea mays L.) is the most farmed crop in Ethiopia, because it is seen as ideal food and cash crop, and is therefore cultivated throughout the country, in various agro-ecologies and socio-economic circumstances. Potentially, maize yield can be increased through the integration of legumes in the cropping system. However, the actual contribution of legumes to maize yield is highly situation specific. Indicating the importance of research done by the research-in-development group N2Africa, of which this study was part. N2Africa “aims to put nitrogen fixation to work for smallholder farmers in Africa”, through improved integration of legumes into the smallholder farming systems. In Ethiopia N2Africa was focussed on a range of legumes, including soybean (Glycine max (L.) Merr). Possible management practices were tested on research stations throughout the country. For this study the field experiment of two of these research stations, Pawe and Bako, were selected, to test a number of management aspects. For maize, the effect of fertilization and previous soybean growth was tested. For soybean cultivation, fertilizer addition, rhizobium addition, and a rotational cropping sequence with maize cultivation was tested. All in all, this set up resulted in nine management treatments, for which yield data was collected by the research stations for three years (three cropping seasons, 2016 – 17 & 18). In addition to this, soil samples and sampling for the 15N abundance method was performed in 2018. This data was able to give an impression of the soil fertility and of the amount and percentage N fixed by soybean.
The aim of this study is to understand the effects of tested management aspects; rotational crop sequence and fertilization, on maize and soybean. For soybean the effect of re-inoculation is also tested. These three management aspects are assessed on four variables; grain yield, soil nutrient levels, nitrogen fixation and the possible farmer’s profit. In order to develop an advice on sustainable intensification of maize and soybean cultivation for smallholder farmers in Ethiopia, these four variables are important. The results indicate variations per location and per year, making generalized advice more difficult. However, when combining results from the two locations and all four variables continuous maize with fertilizer inputs was deemed best. Two rotational treatments were seen as second and third best. A current common farmer practice was second best for both locations. For Pawe a fully fertilized rotation was third best, while for Bako this was a fully unfertilized rotation. Although, the management choice for both locations depends on the variable of interest.
MSc and Bcs thesis, internship reports