Evaluation of mulch combination with Trifluralin and Imazethapyr for chickpea (Cicer arietinum L.) weed control

Chickpea is the second important legume crops and because of high protein level (18-30 percent), has a key role in human diet. Chickpea is a weak competitor with weeds because of its slow growth at the seedling stage, lower height and slow canopy closer. Growing chickpea in weedy condition can suffer yield reduction up to 40 to 90 percent and weed management is one of the most important management methods in chickpea farming. Like another legumes, chickpea is more tolerate to pre-emergence herbicides compare to post-emergence herbicides. Experiments indicated using of one weed control method, can not have a proper and sustainable control on weeds and for this purpose we should integrate weed control methods for sustainable weed management. Mulches is one of the effective weed control method and reduced weed damages. In many cases, pre-emergence herbicides are used in combination with different mulches provide longer duration of weed control and suppress a broad spectrum weed species. Pre-emergence herbicides uses for combining with mulches mostly members of dinitroanilines such a trifluralin and pendimethalin or another pre-emergence herbicides like isoxaben and dichlobenil. In this regard, the goal of this study is evaluating the application of mulch-herbicide combination as a method in chickpea weed control.

The experiment was conducted in completely randomized blocks design with three replications at research farm of Ferdowsi University of Mashhad, Mashhad, Iran, during 2015. Treatments were included the pre-emergence application of trifluralin, imazethapyr and wood shaving mulch and two ways of mulch-herbicide mixtures application (application of herbicide under the mulch and application of pre-mixed herbicide with mulch) with full season hand weeding and full season weed interference as control treatments. For making pre-mixed mulch and herbicide, mulch is sprayed with herbicide in another place on plastic foil and mixed together with rake completely then transported to the field experiment and was spread in field experiment. Studied mulch is a carpentry wood shaved mulch and was spread on the field experiment in 3 centimeter height with rake. For application of herbicides under the mulch, herbicides applied on the soil surface first, then mulch would be spread on the soil surface. The data statistical analysis were performed by Mini Tab Ver 17 and draw the figures with Excel 2013. Means were also compared by LSD (Last Significant Difference) test at 5% probability level.

Results indicated that, application of imazethapyr injured chickpea hardly and stopped chickpea growth. Application of trifluralin and wood shaving mulch alone, decreased weed density and weed biomass and increased chickpea yield significantly. Combination of wood shaving mulch and trifluralin indicated that two different results, trifluralin-mulch mixed had the higher chickpea seed yield (1450 Kg.ha-1) and biomass (3700 Kg.ha-1). Although application of mulch after trifluralin application as pre-emergence, controlled weeds significantly and provide the longer weed duration control in growing season, but also injured chickpea, and decreased it’s suitable density and indicated that the lowest chickpea seed yield and biomass. There was not significantly difference between the trifluralin application alone and trifluralin-mulch combination in three periods of sampling in weed density and biomass it seems the mulch prevent the trifluralin to achieve to the soil surface and decrease weed control efficacy but when trifluralin applied under mulch, weed control efficacy increased and controlled weeds during the growing season significantly. Trifluralin is decomposable when is applied in day light but when it is under mulch it be more stable and increase efficacy compare with application alone.

Through the experiment, mulch is suppress weeds and reduced weed density and biomass significantly and increased chickpea biomass and seed yield. Chickpea is very sensitive to pre-emergence application of imazethapyr and it caused chickpea injury, although this herbicide is labeled for chickpea in Turkey and controlled weeds significantly but in this experiment it caused chickpea injury. Chickpea is less sensitive to trifluralin and trifluralin application, increased chickpea yield significantly and decreased weed density and biomass. It seems that to be trifluralin-mulch combination, when trifluralin applied under the mulch, is suitable and increase the efficacy weed control and decrease the costs with this regard but it caused injury crop and decreased chickpea yield. Pre-mixed combination trifluralin with mulch decreased trifluralin efficacy compare to application Trifluralin under the mulch.