Trickle irrigation rates and soil salinity distribution in an almond ( Prunus amygdalus) orchard

Abstract

Managing the soluble salts in the root zone of a trickle irrigated almond ( Prunus amygdalus) orchard is desirable for tree growth and nut production. This study was conducted to determine the relationships among the volume (50, 100, and 150% of the crop evapotranspiration ( et c) of trickleapplied water and the amount and distribution of soil salinity, Cl −, B, and soluble Na + in a clay loam soil. Irrigation water with an electrical conductivity of 1.5 dS m −1 was applied for four years. The greatest accumulation of soil salinity (electrical conductivity of the saturation soil extract, ec e) of 5.7 dS m −1 was beneath the trickle line for the 50% of et c treatment (14.0 m 3 of applied water tree −1 yr −1). Soil salinity decreased with distance from the trickle line. Increasing the water volume to 100 and 150% of et c (26.9 and 40.3 m 3 tree −1 yr −1, respectively) moves the zone of salt accumulation farther from the trickle line. The apparent leaching fraction based upon the Cl − ratio for the 50% of et c treatment was about 0.05 indicating loss of water by deep percolation within about 1 m of the trickle line. For trees irrigated at 100% of et c, the leaching fraction was 0.22 up to a distance of 1 m from the line, then decreased to 0.06 at a distance of 1.6 m. The leaching fraction for the 150% of et c treatment was from 0.36 within 1 m of the trickle line and then decreased to about 0.34 at 1.6 m from the line. Reasons for the leaching fraction being higher than expected are discussed. Further research is required to optimize the management of trickle irrigation to meet the et c and leaching requirements in young almond orchards irrigated with slightly saline water.