Yield response of corn to irrigation and nitrogen fertilization in a Mediterranean environment

Productivity and resource-use efficiency in corn (Zea mays L.) are crucial issues in sustainable agriculture, especially in high-demand resource crops such as corn. The aims of this research were to compare irrigation scheduling and nitrogen fertilization rates in corn, evaluating yield, water (WUE), irrigation water (IRRWUE) and nitrogen use (NUE) efficiencies. A 2-year field experiment was carried out in a Mediterranean coastal area of Central Italy (175mm of rainfall in the corn-growing period) and corn was subjected to three irrigation levels (rainfed and supply at 50 and 100% of crop evapotranspiration, ETc) in interaction with three nitrogen fertilization levels (not fertilized, 15 and 30g (N)m-²). The results indicated a large yearly variability, mainly due to a rainfall event at the silking stage in the first year; a significant irrigation effect was observed for all the variables under study, except for plant population. Nitrogen rates affected grain yield plant-¹ and ear-¹, grain and biomass yield, HI, WUE, IRRWUE and NUE, with significant differences between non-fertilized and the two fertilized treatments (15 and 30g (N)m-²). Furthermore, deficit irrigation (50% of ETc) was to a large degree equal to 100% of the ETc irrigation regime. A significant interaction “NxI” was observed for grain yield and WUE. The effect of nitrogen availability was amplified at the maximum irrigation water regime. The relationships between grain yield and evapotranspiration showed basal ET, the amount necessary to start producing grain, of about 63mm in the first and 206mm in the second year. Rainfed crop depleted most of the water in the 0-0.6m soil depth range, while irrigated scenarios absorbed soil water within the profile to a depth of 1.0m. Corn in a Mediterranean area can be cultivated with acceptable yields while saving irrigation water and reducing nitrogen supply and also exploiting the positive interaction between these two factors, so maximizing resource-use efficiency.