Multi‐nutrient omission trials for yield optimization: Diagnosing yield‐limiting nutrients for onion ( <i>Allium cepa</i> L.) and tomato ( <i>Solanum lycopersicum</i> L.) under irrigation conditions in Raya Kobo District, Eastern Ethiopia

Abstract Knowing the most yield‐limiting soil nutrient is crucial for closing the yield gap in all crop production systems. The proper supply of balanced nutrients is essential for maximizing the production of onions and tomatoes. The study was conducted to determine the response of onion and tomato to the omission of different nutrients in their growth and yield under open‐field conditions at Raya Kobo District during the 2020/21 growing season, under irrigation. The experiment was laid out in the Randomized Complete Block Design (RCBD) with three replications. A soil sample was taken using an auger before planting for the analysis of the physicochemical properties of the soil. Analysis of variance was computed using R software. The analysis result showed that statistically, the lowest marketable yield of onion was recorded from the omission of nitrogen and the control treatment. In contrast, the highest total unmarketable yield of onion was recorded from the control treatments. Similarly, the combined analysis result for tomato showed that the highest marketable yield was recorded from boron‐omitted plots, which significantly differs from N omitted and control treatments but not significantly from others. In contrast, the lowest total marketable yield was recorded from the control and N‐omitted treatments. There was also a substantial and positive correlation between marketable yield and the number of clusters per plant and the number of fruit per cluster ( p &lt; 0.01). The analysis of variance indicates that N was the most yield‐limiting nutrient for both onion and tomato production, more than any other nutrient. This study was conducted to determine which nutrient was yield‐limiting and did not address what amount was needed. Therefore, optimum fertilizer rate determination on the yield‐limiting nutrient should be conducted.