Investigation of yield-limiting nutrients for rain-fed lowland rice production in the Fogera floodplain of the Amhara Region in Northwest Ethiopia

The productivity of rice (Oryza sativa L.) in Ethiopia is below the potential due to spatial and temporal soil fertility variability and sub-optimal fertilization. This on-farm study was conducted in 2019 and 2020 to determine yield-limiting nutrients, quantify yield gaps, and determine indigenous soil nutrient supply (ISNS) for lowland rice in Fogera floodplain of Northwest Ethiopia. The study comprised the following treatments; NPKSZnB, -N (PKSZnB), -P (NKSZnB), -K (NPSZnB), -S (NPKZnB), -Zn (NPKSB), -B (NPKSZn), and Zero fertilizer (F0). The treatments were arranged in a randomized complete block design considering farmers' fields as replications. The results revealed that the growth and yield of rice were significantly affected by the -N and F0 treatments. However, the other nutrient omissions did not significantly influence the mentioned parameters. The highest (2299.5 kg ha−1) yield response was recorded from the -N treatment. However, very low and insignificant yield responses were recorded from the other nutrient omissions. The average agronomic N use efficiency was 16.7 kg kg−1, which indicated a high probability of yield response to the application of N fertilizer. The lowest (42.4%) ISNS was found for N, while the highest ISNS (>90%) were recorded for P, K, S, Zn, and B. The yield gaps due to the omission of N was 57.6%, while the yield gaps due to the omission of P, K, S, Zn, and B were very low. Therefore, N was found to be the most yield-limiting and most deficient nutrient for the lowland rice production in the study area.