Water Use by Drip-Irrigated Early-Season Peach Trees

The water balance of drip-irrigated peach trees (Prunus persica (L.) Batsch 'Flordastar' on GF-677 peach rootstock) planted in drainage lysimeters (5x5x1.5 m) with a clay loam textured soil located in southern Spain was determined during a 24-month period. Trees were drip irrigated during the night using one lateral pipe per tree row and eight emitters per tree, each delivering 2 L h(-1). Tree irrigation requirements were determined according to daily reference crop evapotranspiration (ETo) by the Penman-Monteith equation, a crop factor based on the time of the year and the percent of ground area shaded by tree canopy. The water balance parameters are shown and discussed. The measured crop water use followed the same trend as the ETo, increasing with time, but reaching a peak in August, a shift of 1.5 months compared with the peak in ETo. The crop coefficient (K-c) was calculated using the measured crop water use and the ETo values. Over the two years, K-c increased gradually, beginning with irrigation in February and extending to early May. There was a brief fall at the end May in K-c, followed by a recovery in early June until a maximum K-c was reached in August. This was followed by a rapid decline in K-c in mid November, when irrigation ended. The crop coefficients calculated on the basis of a water balance would have saved up to 33 and 17% for 2007 and 2008, respectively, in irrigation water compared to the FAO-56 recommendations.