تعيين مدل رياضي شاخص مخروط در خاك هاي لومي رسي منطقه زرقان فارس

Determination of Mathematical Model for Clay-Loam Soil Cone Index in Zarghan Area of Fars Province

In agricultural research, the Cone Index is used for soil penetration resistance of implement, and compaction of soil. Tractor pass, soil moisture content, soil texture, and environment affect this Index. The effect of different passes of tractor on the Cone Index of clay-loam soil (Zarghan area of Fars province) with different moisture content levels were investigated. The parameterʹs effect on Cone Index (three levels of pass and moisture content) with three replications were studied. Also the mathematical model for Cone Index was developed through multiple regression analysis. The results were in agreement of previous studies, which showed the Cone Index was affected directly by tractor passes. It means the soil Cone Index increased with additional tractor passes. Studies on the moisture content levels showed a reverse result (increase in moisture content caused a decrease in Cone Index). Two mathmatical models were obtained in this study by multiple regression analysis. The R2 of 0.86 and 0.88 were obtained for linear and non-linear models respectively. The linear model is suggested for further study for the area since there is not a big difference between the R2 of the two models and also the other model is non-linear with the degree of four.