Soil Shrinkage, Sealing Index and Hydro-Physical Properties of Vertisols as Influenced by Long-Term Cultivation Systems in Northern Egypt

Abstract

Soil shrinkage and sealing index are important for understanding water and solute transport in soils. Effects of long-term cultivation systems on the soil shrinkage, sealing and hydro-physical properties of Vertisols in Kafr El-Sheikh Governorate, Northern Egypt were studied. The cultivation systems were fruit trees (FT), field crops (FC), vegetables crops (VC), and noncultivated soil (NC). Forty eight samples were collected from sixteen soil profiles (three layers: 0-30, 30-60 and 60-100 cm) from different locations. The studied parameters included coefficient of linear extensibility (COLE), shrinkage ratio (SR), potential linear extensibility (PLE), soil sealing index (SI), bulk density (BD), penetration resistance (PR), saturated hydraulic conductivity (Ks) and soil water content (SWC). Long-term cultivation improved soil shrinkage, sealing and hydro-physical properties. Soil organic matter (SOM) and silt + clay contents increased in VC and FC compared with FT and NC systems in all layers (p < 0.05). The BD and PR decreased in all systems, and in VC and FC systems it was prominent compared with NC system. Ks and SWC increased (p <0.05) under VC and FC than in NC system. Low COLE, SR and PLE occurred in all systems particularly in VC and FC system. The VC and FC reduced shrinkage hazards, while high COLE, SR and PLE occurred in NC, indicating shrinkage hazards. The SI was significantly (p <0.05) affected by cultivation systems and sealing was low in soils of VC, FC and FT than NC. Each of COLE, SR and PLE showed a negative correlation (p < 0.01) with SOM, but a positive one with BD and PR (p < 0.01). Each of COLE and SR (p < 0.05) and PLE (p < 0.01) showed negative correlations with SWC and Ks. SI showed a negative correlation with each of COLE, SR, BD and PR (p < 0.01) and PLE (p < 0.05), and a positive one with SWC and Ks (p < 0.05). VC and FC improved the soil shrinkage, sealing index and hydro-physical properties of Vertisols.