ANBAR JOURNAL OF AGRICULTURAL SCIENCES

Abstract

A laboratory experiments were carried out to study and modeling the effect of soil gypsum content on soil shrinkage characteristic curve (SSCC) of gypsiferous shrinkage curve. Soil samples with 100 (G2), 150 (G3), 200 (G4), 250 (G5), 350(G6) g kg-1 gypsum content were prepared by mixing materials from surface soil layer with low gypsum content (G1) 60.6 g kg-1 and sub-surface soil layer with high gypsum content (G7) 433.9 g kg-1. SSCC was measured for each soil sample at the moisture tension of 0,3,6,15,33,100,500,700,1000 and 1500 kPa, the results indicated that SSCC of the studied gypsiferous soils (G1–G7) included only three shrinkage stages. The proportional shrinkage stage formed the bulk part of the SSCC which ranged between 46–84 % for the gypsiferous soils samples G1–G6, the residual shrinkage stage was less than proportional shrinkage stage of the SSCC and ranged between 11–49 % for the gypsiferous soils samples G1–G6, and Zero shrinkage in all samples of gypsum soils. The results showed a significant agreement between the measured and predicated SSCC values calculated. The coefficient of determination ranged between 0.9961 and 0.988 for all studied gypsiferous soils.