Economic impact of irrigation uniformity on crops with high water demand in semi-arid areas

This work aims to quantify the effect of irrigation water distribution uniformity in permanent sprinkler irrigation system in maize, analysing the impact of the irrigation system management on the gross margin of the crop (MB), and to validate the model MOPECO-CU, which takes into account the effect of irrigation uniformity on crop yield. The test was carried out on a 3 ha plot, with two irrigation sectors (S1 and S2) of equal size. In the sector S1, irrigation scheduling was performed trying to cover the water requirement of the crop in the area that received the average of the water applied with the irrigation system. The sector 52was managed by the farmer, according to his experience of more than 15 years cropping maize, applying 19% more of total water than in S1. Three zones were sampled to analyse the crop response. One, representative of 25% of the area that received less water, another representative of 50% and another representative of the 25% that received more water. With a CU = 84%, there are significant differences in crop yield, MB and other indicators of production efficiency between areas receiving different amounts of water, recommending to improve the uniformity of water distribution with the irrigation system, using, for instance, two nozzles in the sprinkler instead of one, and apply around 800 mm ha(-1) to approach the economic optimum of the crop.