Evaluation of the effect of wild barley weed spike cut off in crop rotation on early and late sowing chickpea yield in Lorestan climatic conditions

Chickpea provides N benefit to cereals grown in crop rotation. In addition to the N benefit, chickpea provides a disease break for wheat grown in the crop rotation. Imazethapyr, applied preemergence at the rate of 0.053 kg ai/ha, reduced plant height, delayed plant maturity, and caused leaf chlorosis. Imazethapyr, applied at 0.053 kg/ha, significantly reduced plant height compared with the nontreated or hand-weeded checks. Visual injury symptoms observed with Imazethapyr treatment included chlorosis and delayed maturity of chickpea. There was an apparent rate effect with imazethapyr, when this herbicide was applied at 0.026 kg/ha with sulfentrazone, visual injury symptoms were significantly reduced. The risk of crop injury from the higher use rate of Imazethapyr is probably not commercially acceptable, whereas the injury from the lower use rate probably is acceptable. Pre-emergence application of low-rate of imazethapyr caused minor levels of injury to the plants, it had only minor effects on plant development and yield compared with sulfentrazone. Post-emergence applications of imazethapyr, imazamox and metribuzin, delayed flowering and maturity and reduced yield. Herbicide effects varied with chickpea cultivar. Most of the commonly used herbicides that are recommended for wheat fields weed control are not able to fully control the wild barley (Hordeum spontaneum C. Koch) weed. Hence, utilizing appropriate agronomic strategies for managing this weed is critical. The evaluation of the effect of Wild barley spike cut-off on the previous wheat field, and the effects of chickpea sowing date and weed control measurements in chickpea cultivation in the next year in crop rotation on chickpea yield are among the aims of this study. 

The effect of wild barley weed spike cut off in wheat crop and sowing date and management strategies in chickpea cultivation on chickpea yield in the following year was evaluated in Khorramabad, Lorestan, during 2008-2009 and 2009-2010. The experiment was factorial split plot based on completely randomized block design with three replications. The factorial of the wild barley weed spike cut off in wheat (in two levels: 1- No spike cut off, and 2- Spike cut off) and chickpea sowing date in the following season (in two levels: 1- early sowing and 2- late sowing) was assigned to main plots, and the weed management factor levels in chickpea cultivation at five levels: 1- Pre emergence application of Metribuzin (0.7 kg/ha from Sencor 75%), 2- Pre emergence application of Imazethapyr (0.7 L/ha from Pursuit 10%), 3- Post emergence application of Clethodim (1 L/ha from Select 12%), 4- Hand weeding, and 5- Weedy check was assigned to sub plots. 

Wild barley weed spike cut off in wheat in previous year increased the average grain yield of chickpea by 26.5%. Chickpea grain yield for early sowing was 49.9% higher than late sowing. Pre emergence application of Imazethapyr (0.7 L/ha) and Metribuzin (0.7 kg/ha) had a persistence phytotoxic effect on chickpea. Reducing plant height, leaf brushing, increase the number of branches and delay in reproductive phase, were the negative effects of Imazethapyr herbicide on chickpea. Weed interference in early and late chickpea sowing date significantly reduced 17.8% and 49.8% of chickpea grain yield, respectively. The highest grain yield of chickpea (2309 kg.ha-1) was observed in hand weeding treatment in early chickpea sowing under Wild barley Weed spike cut off in wheat crop conditions, and the lowest chickpea grain yield (449.3 kg.ha-1) was associated to Imazethapyr herbicide application in the late sowing chickpea with under Weed No spike cut off Wild barley in wheat crop in previous season.

The results of this study showed that with the spike cut off wild barley weed in the previous wheat cultivation and preventing current year weed seed rain, we can greatly reduce the population of this grass weed in chickpea cultivation in the following year and consequently reduce its interference effects on chickpea. Chickpea early sowing was also effective in increasing the chickpea yield due to the high efficiency of sowing equipment in controlling wild barley plants and decreasing the population of this weed and, also due to synchrony of crop growth stages with better environmental conditions. In the case of herbicides tested, the Clethodim is an appropriate graminicide for controlling the wild barley in chickpea cultivation, which, of course, achieving a good control requires application in the early stages of grass weeds, and the delay in spraying reduces the control efficiency of this herbicide.