All center pivot systems currently available from the manufacturers can apply different rates of water during irrigation by varying speed. However, these systems generally cannot change the application rate along the length of the pivot boom. The whole system can speed up to apply less water or slow down to apply more. If a pivot is simultaneously crossing areas that are wet (drainage area) and dry (sandy), then a traditional system would have to address one problem of over- or under-irrigate one area or another. Conversely, a variable-rate pivot could apply less water to the wet area and more to the dry area at the same time. The system at the current study is a true variable rate center pivot. The system was developed and tested for two years where the water saving and sugar beet production were measured. Due to the dry weather in most of a season, the differences were clearer than the high rainy year during another season. The results indicated water saving in the second season (102 mm) while low change existed in water use in the first season (36 mm). Sugar beet and sugar production were similar under full irrigation (100% of water balance) and VRI (80% of water balance) for loamy soil (medium quality) for both two seasons, which means that we can obtain the same production with water saving. |
