Suitable Conservation Tillage Machinery for Loam-Silt Soils Based on the Amount of Crop Residue and Principal Component Analysis Method (PCA)

Reduction of tillage operations in conventional systems and its replacement with a reduced tillage and conservation systems is recommended in order to sustainable production in agriculture and preservation of soil and water resources. In this research, the effect of applying three types of conventional tillage machines with different geometry that have less rigidity of soil tillage than conventional tillage machines (Chisel packer, combined tiller and offset disc) on the performance parameters of tillage including Specific draft, specific tillage energy, and weighted average diameter of clods, roughness of soil surface and percent of crop residue on the soil surface. Tillage depth is fixed in 20 cm, forward speed was in three levels (2.5, 4.5 and 6 km/h) and tillage machinery type was in three levels. Double Split plot in Randomized Complete Block Design used in the study in which tillage depth (main factor), forward speed (secondary factor) and the tiller type (sub-secondary factor) were the independent variables. The results showed that the amount of residues remaining on the soil surface after soil tillage was negatively correlated with not only special draft but also with other indices (weighted average diameter of clods and roughness of soil surface), and crop residue after soil tillage was applied as a criterion for comparing soil tillage machinery. The results of the comparison of the ranking of treatments based on two methods (amount of crop residues after soil tillage and the Component Analysis method) showed that the combined tiller and the offset disc at low velocity and Chisel packer at high velocity is recommended for conservation systems of tillage.