Evapotranspiration, crop coefficient and growth of two young pomegranate (Punica granatum L.) varieties under salt stress

Pomegranate (Punica granatum L.) is a drought-hardy crop, suited to arid and semi-arid regions, where the use of marginal water for agriculture is on the rise. The use of saline water in irrigation affects various biochemical processes. For a number of crops, yields have been shown to decrease linearly with evapotranspiration (ET) when grown in salt-stressed environments. In the case of pomegranate, little research has been conducted regarding the effect of salt stress. Our Study Focused on the responses of ET, crop coefficient (K-c) arid growth in pomegranate irrigated with saline water. Experiments were conducted using lysimeters with two varieties of pomegranate, P. granatum L. vars. Wonderful and SP-2. The plants were grown with irrigation water having an electrical conductivity (ECiw) of 0.8, 1.4, 3.3, 4.8 and 8 dS m(-1). Plants were irrigated with 120% of average lysimeter-measured ET. Seasonal variation in ET, crop coefficient (K-c) and growth were recorded. Variation in daily Er was observed 1 month after initiation of the treatments. While significant seasonal ET variation was observed for the EC-0.8 treatment, it remained more stable for the EC-8 treatment. Salinity treatment had a significant effect on both daily ET (F = 131, p < 0.01) arid total ET (F = 112.68, p = 0.001). Furthermore, the electrical conductivity of the drainage water (ECdw) in the EC-8 treatment was five times higher than that of the EC-0.8 treatment in the peak season. Fitting the relative ET (ETr) to the Maas and Hoffman salinity yield response function showed a 10% decrease in ET per unit increase in electrical conductivity of the saturated paste extract (ECe) with a threshold of 1 dS m(-1). If these parameters hold true in the case of mature pomegranate trees, the pomegranate should be listed as a moderately sensitive crop rather than a moderately tolerant one. Fitting 30-day interval ETr data to the Maas and Hoffman salinity yield response function showed a reduction in the slope as the season progressed, Thus using a constant slope in various models is questionable when studying crop-salinity interactions. In addition, both of the varieties showed similar responses under salt stress. Moreover, the calculated value of K-c is applicable for irrigation scheduling in Young pomegranate orchards using irrigation water with various salinities. (C) 2010 Elsevier B.V. All rights reserved.