Effects of weed interference duration on yield and yield components of chickpea (Cicer arietinum) in two different production system

Chickpea (Cicer arietinum) is the third most important pulse crop in the world, grown widely across Asia and the Middle East. Weed is one of the main limiting factors in Chickpea (Cicer arietinum) production. Several characteristics of chickpea (Cicer arietinum), such as slow plant emergence, short plant height, and chickpea morphology allow weeds to compete effectively. To investigate the effect of weed interference duration on yield and yield components of chickpea (Cv. Hashem) grown under conventional and organic condition, a field experiment was conducted at Sabzevar in 2013-2014. Experiment was conducted as split plot in a randomized complete block design with three replications. Experimental factors were conventional and organic conditions as the main plots and duration of weed interference (0, 2, 4, 6 and weeks after emergence 8 (weedy)) as sub plots. Agronomy management in conventional farming including plowing with Moldboard, use of chemical fertilizers based on soil test and non-seed inoculation and in organic farming including Chisel plowing, application 3 ton.ha-1 compost, seed inoculation and foliar application with organic liquid fertilizer. Other agricultural operations were similar in both tillage systems. Analysis of variance showed that cultivation system had significant effect on number of branches, number of pods per plant, number of seeds per pod and economic yield whereas plant height and biological yield was not affected by cultivation system. Weed interference during statistically influenced all traits except weed density and plant height. cultivation system* weed duration had significant effect on weed dry matter, plant height, number of branches, number of pods per plant, number of seeds per pod and economic yield. Means comparison showed that organic farming had 13.24% and 59.47 lower weed density and weed dry matter compared with conventional, respectively. In organic system, Chickpea had more plant height, number of branches, number of pods per plant, number of seeds per pod, biological and economic yield than conventional system. Increasing of interference duration was decreased plant height (17.21%), lateral branches (33.34%), the number of pods per plant (61.79%), the number of seeds per plant (73.12%), biological yield (54.25%) and economic yield (77.22). Fitted logistic regression function coefficients showed that the onset of yield loss was earlier (24.5 days after emergence) in conventional condition while in organic condition the onset of yield loss was postpone to 31.64 days after emergence. In conclusion, results showed in both conventional and organic condition, weed interference reduces economic yield. In organic farming weed interference until 4 weeks and in conventional weed interference until 2 weeks after pea emergence had not significant reduction on yield.