Comparison of the Effects of No Tillage, Minimum Tillage and Conventional Tillage on Dry Land Wheat Yield in Pebbly Field in Tropical Region

The current study was conducted to compare different tillage methods on wheat yield in pebbly dry land areas done within three years (2006-2008) in north Khouzestan (Baghmalek city) in randomized block design with five treatments and four replications. The experimental treatments were:(1)chisel plow +seed-drill, (2)Semi plow(mold board plow with remove mold board)+seed-drill, (3)no-till-drill, (4)sweep plow +seed-drill and (5)conventional method(mold board plow+ broadcasting seed and fertilizer+ sweep plow). These treatments included minimum tillage (treatments 1, 2 and 4), no tillage (treatment 3) and conventional tillage (treatment 5). Complex variance analyses of three years data showed that there was no significant difference between tillage methods and interaction of tillage methods with year in soil moisture content in different plant growth stages (stem, flowering, and filling seeds stages) but years were different in this factor. Variance analyses of data showed that there was no significant difference between different tillage methods in percent of organic materials in different soil depths in the end of the project. However, no difference in tillage methods in the amount of organic material has been analyzed based on the pebbly conditions. The complex variance analyses of data also showed that tillage methods had significant effect on grain yield and other agronomical factors, except plant height and harvest index. According to the results any devices cause to back more gravel and cobblestone into sub soil layer provide more grain yield. Therefore, mold board plow resulted in maximum yield in three experimental years which were different in amount and distribution of rainfall, and also in third year the amount of rainfall was considerably low. The grain yield averages of three years were 1333, 1558, 1190, 1080 and 1787 Kg.ha-1 for chisel plow, semi plow, no-till-drill, sweep plow and mold board plow respectively.