Modeling soil erodibility by water (rainfall/irrigation) on tillage and no tillage plots of a Helianthus crop using soil analysis, field measurements, GIS and kriging geostatistical models

The study presents a spatial modeling approach of soil erodibility (K factor) by water (rainfall and irrigation) on conventional tillage (CoT) and no tillage (NOT) treatments of a Helianthus annuus crop using field measurements, soil analyses, GIS and Kriging geostatistical models. A split-plot design with 4 treatments×3 replications of experimental field plots (with a south-east facing 7.5 % slope) was used. At each plot, topsoil samples (0–5 cm) were collected in a Grid pattern to determine texture (clay, silt, sand, very fine sand and gravel contents), organic matter content (OM), soil’s structure and soil’s water permeability classes. A Global Positioning System (GPS) receiver was used to identify the sampling locations and the 40 top soil samples were air-dried, and passed through a 2 mm mesh to determine soil texture by the Bouyoucos method. Organic matter was analyzed by chemical oxidation with 1 mol L^-1 K₂Cr₂O₇ and titration of the remaining reagent with 0.5 mol L^-1 FeSO₄. The soil structure and the soil’s water permeability classes were determined according to USDA classification system. Soil erodibility by water modeling of K factor (t ha h ha−1 MJ−1 mm−1) was based and estimated using the nomograph equation of Wischmeier model by incorporating it in a developed GIS spatial model using Kriging geostatistical models. Results of Anova statistical analysis (P=0.05) between K data groups revealed that the 2 tillage systems and the 4 management treatments were significantly different. Moreover, it was found that no tillage system and treatment-No Tillage with Vegetation Cover were the best tillage and agricultural practices for hillslope farmfields, and can be regarded as potential ecological good agricultural practices, in order to reduse soil erodibility by water, erosion and runoff risk and preserve the soil environment and its valuable nutrients.