the effect of different methods of tillage, accompanied by plant residue management and different levels of nitrogen application, on yield and yield components of rainfed wheat (cv. agosta) in fars province climatic conditions

to investigate the changes in yield and yield components of dry land wheat (triticum aestivum l. cv agosta), under the influence of residue and nitrogen levels and different tillage practices, a field experiment was conducted during the 2006-2007 growing season, in the agricultural research station of the college of agriculture, shiraz university, iran. the experiment was designed as a split-split one based on completely randomized blocks with 4 replicates. the treatments were comprised of three tillage practices (t1: moldboard plow + two perpendicular passes of disk harrow, t2: chisel plow + two perpendicular passis of disk harrow, t3: two perpendicular passes of disk harrow) as main plot, three levels of residue left on the soil surface (0, 50 & 100 % by weight of past year wheat residue, r1, r2 & r3, respectively) as sub-plot and three nitrogen levels (0, 100 & 200 kg n/ha n1, n2 & n3, respectively) from urea source as sub-sub plot. the results indicated that nitrogen application significantly increased wheat yield and yield components. main effect of residue on seed yield and 1000 seed weight was significant, leaving the residue on soil surface was associated with increased 1000 seed weight as well as grain yield. tillage practices also affected seed yield significantly. the highest level of seed yield was achieved at t3 (99.01 g/m2). among the grain yield components, 1000 grain weight and grain number per spike were affected by interaction of r×n with the highest 1000 seed weight and grains per spike obtained from n3×r3 treatment. overall, this research revealed that under similar agro-climatic conditions, leaving plant residue on soil surface along with n application could result in higher yield in dry land wheat through improved traits of 1000 grain weight and number of grains per spike.