| Agriculture is the largest user of fresh water in the world. Therefore, any improvement in the efficiency of irrigation water use will result in cost reduction and the possibility of larger irrigated areas. This communication presents a precision irrigation system based on a wireless network of sensors and actuators in which a high level of control is achieved by means of valve automation. Water needs are calculated based on the crop characteristics, soil information, and the design of the irrigation system. Regional real-time weather data were obtained from the California Irrigation Management Information System (CIMIS). A new software system was developed to manage and control multiple valve groups according to different crops and strategies, and to make decisions on when and for how long to irrigate. The system was tested in almonds and walnuts where strategies based on evapotranspiration, stem water potential, and grower opinion were carried out. A total of 36 five-tree units were controlled with valves operated by the control software. Water use, yield, and nut quality were measured to analyze differences between the irrigation strategies. A cost/benefit analysis was also done using current water costs in different California agricultural regions. The use of this variable rate system to control irrigation based on evapotranspiration resulted in water savings of 1,776 m3/ha for almonds and 995 m 3/ha for walnuts compared to normal grower control. Despite the reduction of water use, at current water costs these savings will not compensate for the differences in yield. |
