Diagnosis of Performance of Four Tillage Methods by Analytical Hierarchy Procedure (AHP) and Overall Tilth Index in Clay Vertisols

This study was carried out during seasons 2018/2019, and 2019/2020, in Tayba Block-the Sudan - Gezira central clay plains, to evaluate the field performance of four land preparation methods using three tillage equipment: chisel plow "intensive tillage", disc harrow "medium tillage", ridger "minimum or reduced tillage" and no tillage machine. An overall tilth index to reflect field performance of tillage methods was determined from four measured soil tilth indicators (bulk density, porosity, aggregate uniformity, and penetration resistance). Diagnosis of land preparation methods was made using analytical hierarchy procedure (AHP) for ranking tilth indicators by weight assignment and determination of overall tilth index using a linear relation. The results show that Bulk density of the soil surface layer was reduced by tillage implements compared to no till. High significant difference at 1 % level was observed between reduced or no tillage and intensive tillage by chisel or disc harrow on average percentage Soil porosity. Bulk density and Soil porosity are inter-related with similar trend. Aggregate stability showed highest value with no till treatment followed by chisel plow, while those obtained by harrow or ridger implements do not differ significantly. Penetration resistance was significantly lowered by tillage implement compared with using no tillage machine. The highest reduction is achieved by disc harrow followed by ridger and the least reduction is made by chisel plow. Penetration resistance is interrelated to Bulk density. Using analytical hierarchy procedure ranked the tillage indicators in descending order by weight values of 1.01, 0.62, 0.29 and 0.12 for Penetration resistance, Bulk density, Porosity, and Aggregate particle stability respectively. The diagnosis of tillage alternatives by development of the overall tillage index resulted in ranking tillage methods in descending order of preference as: ridger, disc harrow, chisel plow, and no tillage machine. It is thus recommended to use reduced tillage "ridging only" as the most technically feasible tillage method achieve an optimal seedbed with minimum energy input.