Effect of nitrogen fertilizer and herbicides on weed control and wheat grain yield under subtropical conditions

Abstract

In order to study the interaction effect of nitrogen (N) rates and herbicides (H) on weed control and wheat grain yield, this experiment was carried out in South-west of Iran which has subtropical climate, mild winters, and hot, dry summers. The experiment was a factorial using randomized complete block design with three replications. Four rates of N fertilizer (urea) (50, 100, 150, 200 kgNha-1) and three herbicide treatments including Apirus (Sulfosulfuron), Tapik (Clodinafop-Propargyl) + Granestar (Tribenuron-Methyl), Tapik + Duplosan Super (Dichlorprop-P + MCPA + Mecoprop-P) along with unweeded control treatment were examined. The increase of N rates increased the density of narrow-leaf weeds and reduced herbicides control efficiency. Herbicide susceptibility of weed species was influenced by N. The highest weed control efficiency was recorded in Apirus which was significantly different from the other two herbicides. The interaction effect of N×H on grain yield was significant (P<0.01). The highest and the lowest wheat grain yield were respectively recorded in Apirus and combination of Tapik + Granestar. The use of Apirus, Tapik + Granestar and Tapik + Duplosan Super increased the wheat grain yield 43%, 35%, and 25%, respectively in relation to unweeded control. Higher grain yield in Apirus treatment was due to further control of the weeds (93%). Generally, the results indicated that Apirus herbicide was more efficient than others in controlling narrow and broad-leaf weeds. Unlike other herbicides treatments, Apirus had likely similar efficiency in all N rates while in other herbicide treatments the increase of rates of N and the weed biomass decreased the weed control efficiency.