International Water & Irrigation

20 Introduction The relatively small number of publications on irrigation and fertigation is most likely because persimmon cultivation has been traditionally important in areas of Korea and China where the precipitation is often abundant and irrigation is not crucial. Over the last ten to fifteen years, persimmon production has emerged as an important crop in areas of the Mediterranean basin, due, among other things, to the selection of new and productive cultivars like the cultivar ‘Rojo Brillante’, which is well adapted to the Mediterranean soil and air temperature conditions and astringency can be easily removed. Water can be the main limiting factor for tree productivity in the Mediterranean and irrigation is commonly practiced to achieve optimum yield and fruit quality. The efficient management of irrigation and fertilization in persimmon production in Spain is not only important to optimize the use of inputs, but also for mitigating the high sensitivity to salinity of persimmon trees. Irrigation management Irrigation scheduling of crops is often performed based on a soil water balance, in which crop evapotranspiration (ETc) is estimated using the reference evapotranspiration (ET a) and the crop coefficient (Kc). Studies performed recently in northern Israel evaluated the irrigation influences on plant growth, yield and water use of ‘Triumph’ persimmon trees. During these trials, the researchers observed that trees increased in yield and vegetative growth in response to water applications up to an irrigation regime around 70 and 100% of ETo, for both summer and autumn periods. In Valencia, Spain, a study was initiated to determine the water needs of persimmon trees under Mediterranean climate using several tools including sap flow gauges calibrated with whole canopy gas exchange determinations, as well as determinations of the soil water balance using soil capacitance probes. The chronic scarcity in the Mediterranean basin of water reserves for irrigation, might result in irrigation being the main limiting factor for persimmon production in the area. In conditions of water shortage, restricted deficit irrigation (ROI) has been shown as a suitable technique that can be used by growers to reduce the amount of water to apply in some crops with none or minimal reductions in yield ROI has become increasingly common practice since the Nineteen Eighties as a strategy to reduce tree growth of vigorous trees and to save water. Following the ROI procedure means that growers must restrict irrigation levels during phenological periods when fruit growth is less sensitive to soil water deficit. Therefore, the use of ROI techniques requires the knowledge of the crop sensitive periods to deficit irrigation, which are different from each crop depending on their agronomic and physiological characteristics. In a previous study performed on mature ‘Rojo Brillante’, persimmon trees, grown in a drip-irrigated commercial orchard located in Valencia, Spain, it was observed that fruit weight was reduced by ROI applied at any time during the season, with the greatest reduction resulting from ROI applied in mid-summer. Notwithstanding, ROI enabled water savings of up to 20% without any reduction in yield, while the increase Gauging responses of the persimmon tree to water and nutrients to design efficient fertigation protocols Water can be the main limiting factor for tree productivity in the Mediterranean and irrigation is commonly practiced to achieve optimum yield and fruit quality