Optimized regulated deficit irrigation for limited volumes of irrigation water and simultaneous crops. The ORDILS methodology

In regions with scarce water resources, as is the case of most of Spain and other Mediterranean countries, a commonly used methodology to regulate the use of irrigation water by farmers is for the regulatory authority to establish a maximum volume, which is controlled through meters installed on farms. Producers of extensive annual crops in these areas have to tackle two significant problems, among others. The first is to decide which crops to grow and the total area to devote to each one for the next crop year, depending on the availability of irrigation water and cropping area. This is complicated by the uncertainty of future weather conditions, especially in the current climate change scenario. The second challenge is to distribute, as efficiently as possible, across the season, the available amount of water in order to achieve maximum crop yields/returns, while avoiding at least the most profitable crops suffering water deficit if adverse climate conditions increase the need to irrigate beyond expected levels and the water resources available. To solve such problems, our research team proposes the development of an optimization algorithm called ORDILS (Optimized Regulated Deficit Irrigation for Limited volumes of irrigation water and Simultaneous crops), which is the result of experience accumulated in national Spanish projects, and other previous European projects. This algorithm, using an initial reference situation, and depending on the water available, as well as the expected crop yields and profitability according to the amount of irrigation water applied, will be able to adapt irrigation scheduling, and even determine the optimum area to be cultivated, with the intention of maximising the farm’s profitability. To demonstrate the applicability of ORDILS a 2-year field experiment with three crops (purple garlic, barley and maize) is being carried out in Albacete (Spain). Thus, three experimental strategies are considered: a) non-deficit irrigation conditions (control); b) the strategy followed by a typical farmer (who attempts to apply non-deficit irrigation and, if water is short, uses the water destined to the least profitable crops to satisfy the water demands of the most profitable; garlic, in this case); and c) the methodology proposed by ORDILS. The aim of the experiments is also to analyse the effect of ORDILS on crop yield, harvest quality and physiological response, the agricultural and economic productivity of the irrigation water and the water footprint, and the profitability of a typical farm managed by this regulation system. The results of the first year were promising but the increase on the final profitability was lower than expected (2%). This resulted from a beneficial distribution of precipitation throughout the growing season that permitted the avoidance of water deficit by garlic and barley during the Spring, the most sensitive period for these crops. Consequently, during this first year the effect of ORDILS was highly conditioned by good climatic conditions for the objectives of the farmer. Nevertheless, under drought conditions it is expected ORDILS can significantly increase the profitability of the farms compared with the profitability obtained by the typical farmer.