Onion crop response to different irrigation and N-fertilizer levels in dry Mediterranean region

Abstract

Due to the water scarcity in dry Mediterranean condition, determination of water and nitrogen (N) fertilizer needs is a major challenge for crop production and environment protection. Pot experiments under open field conditions were conducted for two consecutive years (2016 and 2017) to assess the effects of various levels of N-fertilizer and irrigation on onion crop, following a 4×3 factorial experiment arranged in a randomized block design with four N-fertilizer rates (0, 40, 80, and 120 kg N ha-1), and three irrigation levels (100, 80, and 60% of the seasonal water use), with three replications. Results indicated that the initial soil N-content (about 60 kg N ha-1) was sufficient to meet crop nitrogen requirements. However, results indicated that onion crop was sensitive to water stress, so that the highest total bulb yield (BY, 19.1 t ha-1), dry matter in bulbs (DM, 2.97 t ha-1), and water productivity (WP, 1.9 kg m-3) were found under full irrigation compared to the deficit conditions. BY, DM, and WP were predicted to be increased linearly with increasing levels of irrigation. The developed equations could be used for predicting onion crop yields under similar agro-pedo-climatic context, and as a tool for rational management of limited irrigation water.