Effect of deficit irrigation on yield and water use efficiency of onion (Allium cepa L.) in arid zones

Efeito da irrigação deficitária na produtividade e na eficiência do uso da água da cebola (Allium cepa L.) em zonas áridas

Abstract

Onion is considered a major vegetable crops all over the world. In arid zones water deficit can affect the yield of crops such as onion. Through this research, four levels of irrigation were used (100% of the calculated crop evapotranspiration ET100, 80% of the calculated crop evapotranspiration ET80, 70% of the calculated crop evapotranspiration ET70, and 60% of the calculated crop evapotranspiration ET60) in combination with two levels of fertilization (100% of the recommended fertilization NPK100 and 75% of the recommended fertilization NPK75). The total yield (fresh weight) of each experimental unit were harvested, weighed, and then sorted into marketable and unmarketable and both the overall and the marketable water use efficiency were calculated. The results were statically analyzed using the ANOVA analysis and the means were compared using the Duncan LSD method. Principle Component Analysis (PCA) was used to classify the treatments into clusters. Results used indicated that the water use efficiency of onion increase if a mild drought stress (85% of the calculated crop evapotranspiration) were exerted on the plants at 100% of the recommended fertilization level. The availability of fertilizers helps the plant manage the drought stress while keeping an adequate level of yield. The lack of fertilizers combined with the drought stress resulted in rapid decrease in the yield thus decreasing the water use efficiency. The recommended water deficit level under these circumstances would be 88.9% of the plant water requirements.

Keywords:
deficit irrigation; onion; water use efficiency