Total evapotranspiration of apple trees with drip irrigation in high density orchard

Due to the changes in management tecniques in apple production the importance of irrigation has lately increased in Latvia. This study evaluated the effects of drip irrigation on the productivity increase, fruit quality changes, tree development and other cultural paramers in Latvia climate conditions where irrigation is required mainly as an additional soil moistening measure due to the uneven distribution of rainfall. In the trial, held between May and September from 1998 to 2007 years, the total evapotranspiration of apple trees, the root area of apple trees and of perennial grass present between the rows were estimated by using the soil layer balance methodology. Several methods of evapotranspiration calculation have been compared. In the observation period the total mean evapotranspiration varied from 2.7 to 3.0 mm or 4.1-4.9 L plant^-1 day^-1, depending on the model used. In July of 2001 the total maximum evapotranspiration was calculated as 5.3 mm day^-1 while in September of 1998 the minimum total evapotranspiration was estimated as 0.9 mm day^-1.