Summary The potential yield of improved maize varieties usually cannot be fully realised mainly due to inappropriate soil nutrient management practices in most parts of Ethiopia. Site-specific fertiliser recommendations are rarely used in the farming systems of Ethiopia. There is also a lack of data to develop or validate decision support tools for targeting specific crop production. A study was conducted for three consecutive rainy seasons (2016–2018) in the maize belt of the north-western parts of the Amhara National Regional State of Ethiopia. The objectives were to obtain the maximum achievable yield potential of maize, determine the most yield-limiting nutrients and create a database of maize responses to applied nutrients so that decision support tools could be developed for the study areas. Treatments were individual nutrients (nitrogen (N), phosphorus (P) and potassium (K)) and combinations of the three. In some treatments, NPK was also combined with sulphur, zinc, lime and compost. Two hybrid maize varieties (BH-540 and BH-660) adaptable to the study areas were used. BH-540 was used for the Mecha district, while BH-660 was used for the south Achefer, Jabitahnan–Burrie–Womberma districts. Maize yield increased by more than 50% due to fertiliser applications compared to without fertiliser. The study showed that the possibility of increasing maize productivity to more than 12 t ha-1 for the study sites. The most yield-limiting nutrient in the study sites was N, followed by P; K was not a yield limiting. Without N the yield of both varieties was non-significant from the control (without added nutrients). Maize grain yield did not respond to application of lime, compost, zinc and sulphur. The result also showed very high variability across sites, indicating that it is important for policymakers, farmers and investors to consider site-specific fertiliser recommendations. Finally, a database containing intensive plant response to NPK for maize was generated and could be used as input in site-specific decision support tools development.

Continuous conversion of land for different agricultural production purposes has resulted in degradation of soil resources. Rehabilitating soil quality through sustainable land management is one of the most pressing agenda in agriculture. Hence, this study was conducted to evaluate the trends of major soil quality after the introduction of A. decurrens tree-based farming in Guder watershed. Soil samples were collected from 5 land use types, 2 soil depths, and 3 slope positions with 3 replications and then analysed for selected soil physicochemical quality indicators. Selected soil physicochemical indicators were subjected to three-way ANOVA. The result revealed that the highest clay particles and soil bulk density were recorded at A. decurrens tree farmland and cropland soils, respectively. The maximum soil pH was recorded from natural forest (5.99), subsurface soil layer (5.56) and lower slope (5.57). The lowest soil organic carbon and total nitrogen contents were observed in cropland. Greater available phosphorus (13.58) mg kg −1 was obtained in the topsoil depth of A. decurrens tree farmland at the lower slope. Among the studied soil quality indicators total nitrogen, cation exchange capacity and soil pH were strongly and Zerfu Bazie ABOUT THE AUTHORS Zerfu Bazie is a researcher at Adet Agricultural Research Center, Ethiopia. His research interest focuses on the generation of climate smart soil management technologies that increase agricultural productivity and reduce the emission of greenhouse gases as well as enhances the resilient of smallholder farmers during climate shocks.

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Nitrogen is a critical yield-limiting plant nutrient for crop production in Ethiopia. The demand for synthetic fertilizer is significantly increasing. Urea is the main source of synthetic nitrogen fertilizer that mainly applied in the surface resulting in significant nitrogen loss. UREA stabil fertilizer is urea with N-(n-butyl) thiophosphoric triamide (nNBPT) that reduce the rate of urea hydrolysis by urease to reduce nitrogen loss and increase crop productivity. The research was conducted in Yilmana Densa district, Ethiopia for two years to evaluate the performance of UREA stabil compared to urea. The research evaluated the effect of UREA stabil fertilizer technology on bread wheat and tef at Nitisol and Vertisol. The finding of this research denies our prior hypothesis that UREA stabil could give better yields of tef and wheat with lower rates of nitrogen at single application rate compared to urea. Reducing the amounts of nitrogen by one third using UREA stabil resulted in an intolerable significant yield penalty for all the study sites and both years on wheat. Both the grain and straw yields were increased by splitting the UREA stabil , indicating that the enzyme that hydrolysis urea was merely inhibited. Considering a nonsignificant yield difference between the conventional urea and UREA stabil for all crops, soils, rates, and forms of applications UREA stabil is not promising. Further research with different rates of nNBPT as well as different nitrification inhibitors