The Combined Effect of Soil Gel-Conditioner and Irrigation Water Quality and Level on: I. Soil Water Retention and Availability, Water and Salt Distribution in Sandy Soil PDF

Keywords

irrigation, soil, gel-conditioner

Abstract

This study was conducted to investigate the combined effect of soil gel-conditioner (Aquasorb) addition to calcareous soil (Typic Torripsamments) and irrigation water qualities under different water requirements. The soil gel-conditioner was added to the soil surface (0- 0.06 m) at the rates (C): 0.0, 0.3, 0.6 and 0.9% (on dry weight basis). Natural irrigation waters having different qualities (ECw): 0.45, 3.10 and 6.25 dS/m were used at three irrigation levels (IL): 40, 60, and 80% of evaporation from free water surface (Ev). The effect of ECw on the relative water absorption capacity (RWAC) was determined. The gravimetric soil water content a field capacity (WFC), and at permanent wilting point (WPW) were determined and the available water (WAW) was calculated. Soil expansion and bulk density (Db) were also determined. In addition, the volumetric soil water (θ) and salinity (ECs; for extract of 1 soil: 2.5 water) profiles were evaluated. The RWAC was exponentially decreased with increase of ECw. Although, the gravimetric soil water contents at field capacity, permanent wilting point and available water were significantly increased with increase of C, they were significantly decreased with increase of ECw. These relationships were illustrated exponentially with r> 0.910. Although the soil surface layer expansion was increased due to the increase of C, it was clearly decreased with increased of ECw. This expansion resulted in peculiar bulk densities for surface layer. The Db decreased as C increased, but the rate of decrease was reduced with increase of ECw. A linear relationship between Db, C and ECw was obtained with r=0.968. In general, it was found that the volumetric soil water content of sandy soil profiles increased with increase of C especially at the treated surface layer, and increased with increase of ECw. Increasing of IL resulted in an increase of soil water content at treated surface layer. The ECs values at treated surface layer significantly increased by increase of C and ECw. The ECs of treated surface layer was increased with increase of IL with the exception of 80% were ECs was lower than that at 60% irrigation level. Generally, the irrigation water quality should be considered in the selection and management of soil gel-conditioners beside their rate of addition.