Relationship Among In-Situ and Laboratory Determinations of Soil Field Capacity Under Arid Conditions

Abstract

To investigate the relationship among field capacity (FC) in–situ and laboratory determinations of soil moisture content under different applied pressures of different soil textural classes, one hundred and sixty-eight of surface samples were collected. The collected samples were classified to seven groups based on the USDA texture triangle. Simulated field determinations of in-situ FC were done and the obtained results revealed that the elapsed time to reach FC and the values of soil moisture tension are different according to soil textural class. Generally, increasing water-holding pores and/or fine capillary pores, both moisture tension at FC (hfc) and elapsed time to reach it after heavy irrigation (tfc) are increased. Sand and loamy sand soils, have the highest significant correlation coefficient between in- situ FC and soil water content balanced with 60 mbar of applied pressure. While sandy loam soil achieves the highest significant value of correlation coefficient, at 100 mbar of applied pressure. The significant correlation coefficients among FC - in situ - and soil moisture content balanced with 330 mbar of applied pressure of the other soil textural classes under study are found.

Keywords

• field capacity
• soil water content
• soil water depletion rate
• soil water characteristics data
• pore size distribution