Crop Response to Balanced Nutrient Application in Northwestern Ethiopia

Enhancing crop productivity through soil fertility management, primarily by using synthetic fertilizers, has received prior attention in Ethiopia. Recently, a soil fertility map of the Amhara National Regional State developed by the Ethiopian Ministry of Agriculture and Natural Resources (MoANR) and Agricultural Transformation Agency (ATA) indicates that, in addition to the conventional nitrogen and phosphorus-containing fertilizers (urea and DAP), the demand for potassium, sulfur, zinc, boron, and other micronutrients requires synthetic fertilizers. This research was designed to validate the developed soil fertility map with the response of major cereal crops (maize, tef, and wheat) at Burie-womberma, Debre-Elias, Enemey, South Achefer, and Yilmana Densa districts to the application of potassium, zinc, and boron-containing fertilizers depicted on the map. The findings of the research showed that nitrogen and phosphorus are still the most yield-limiting nutrients. The response to potassium was observed under rare cases that did not fit with the developed soil fertility map, but the finding was verified for one year, and those rare cases were not observed. Application of zinc and boron-containing fertilizers didn't show any significant yield advantage, indicating that fertilizers containing NPS nutrients with a major focus on NP are sufficient. Under the Vertisols (Bichena), NPSZnBK (nitrogen, phosphorus, sulfur, zinc, boron, and potassium) containing fertilizer was showing a yield advantage over NP fertilizer, but upon verification of the findings of the two-year experiment with simple treatments, there was no significant effect of the potassium, zinc, and boron fertilizer over NPS alone. Based on the findings of this research, zinc, boron, and potassium are not yield-limiting nutrients for the study areas and crops. Therefore, potassium, zinc, and boron fertilizers recommended by the fertility map of the region shall not be used anywhere without research-based field verification and recommendations. Furthermore, we recommend monitoring the state of plant nutrients in the soil and crop responses to potassium, zinc, and boron fertilizers every 5 to 10 years.