Chemical management efficacy in conventional and conservation agricultural systems at cold region of Khorasan-Razavi

Conservation agricultural systems may considred as a solution to loosing arable soil in conventional system. We studied the effects of conservative agricultural systems compared to conventional systems on chemical weed control efficacy at the farm of Jolgeh-Rokh research station, Khorasan Razavi province, during 2014-2017. Crop rotaton was sugarbeet-barley-corn-wheat. The experimental designe was randomized complete block design aggranged in split-split plot with three replacations. Treatments were three types of tillage (conventional, reduced and no-tillage) as main plot; crop residue percentage (left on the ground from previous crop in rotation; 0, 30 and 60 percent) as sub plot and methods of weed control (hand weeding, recommended herbicide and check plots) as sub-sub plot. The results showed that application of herbicides significantly decreased weed dry matter (57%) and weed density (31%) and increased sugar beet root yield (64%) compare to the weedy check; however, weed reduction was not enough to prevent root yield loss in conservational tillage systems. Residue levels showed no significant effects on root yield of sugarbeet. The effects of tillage systems, levels of residues and even chemical control did not affect the grain yield of barley, despite the effects on weeds. Tillage in corn significantly decreased the weeds (83% to no-tillage); as a result, corn grain yield increased significantly in conventional and reduced tillage systems (3.53-ton ha-1 and 4.33-ton ha-1, respectively) compared to the no-tillage system (3.14-ton ha-1). Different levels of plant residues had no effect on corn yield, but chemically weed control caused a significant increase of yield (23%) as much as manual weeding treatment. Reduced tillage system with 30 percent of the residues and the chemical control of weeds was the best treatment for grain yield of wheat.