Response of rice and weeds to seed priming under different weed management in direct-seeded

Backgrounds and Objectives:

Direct seeding is being developed in many Asian countries as a new technology that farmers are tending to use this technology in current years considering that it has appropriate economic efficiency, faster and easier cultivation, less labor force, more mechanization and shorter growth period than transplanting cultivation and due to discontinuous irrigation, less methane emission. But what makes it mainly obstacle are weeds.The use of seed priming can be one of methods that it can compensate the paucities of direct seeding and get promote seed quality. Seed priming also can active the initial germination mechanisms before planting and many benefits were mentioned for this treatment that the most significant of them is increasing the percentage and rate of germination. Indeed these plants expand their root system in shorter period of time compared untreated seeds. They are also reached to autotroph stage earlier by absorbing more water, nutrients and producing photosynthetic part. 

Materials and Methods:

The field experiment was conducted in Neka in 2018. The experiment was performed as a factorial in randomized complete block design in three replications. Experimental treatments include  seed priming in four levels 1- no priming, 2- hydropriming (priming with water), 3- priming with humic substances (10 g per 1.5 liters of water) 4- priming with auxin hormone (1.5 cc in 1.5 liters of water) and also, weed management at five levels 1- no weeding, 2- council active herbicide (15 g per 20 liters of water), 3- twice weeding (one month after planting + before the earing stage), 4- council active herbicide (15 g per 20 liters of water applied about one month after planting) + weeding (1.5 months after planting) and 5- complete weeding (weeding of all weeds during the growing season). 

Results:

Based on the results, by applying seed priming with humic acid, the maximum plant height, ear length and number of plants m-2 were obtained and complete weeding caused the maximum plant height, fertile tiller, total tiller and ear length. Also, seed priming with humic acid along with complete weeding caused the highest filled grain number (79.67 number) and total grain number (90 number), 1000-grain weight (23.47 g), grain yield (2327 kg ha-1), biological yield (11220 kg ha-1). Based on total weed density and biomass, in all three stages of sampling, the lowest amount of weed biomass and density was obtained with application of humic acid priming along with council active herbicide + weeding, which was not significantly different from application of humic acid priming and twice weeding and application of auxin with council active herbicide + weeding and twice weeding. Overall, the findings of this study indicate the effect of priming of rice seeds especially with humic acid and auxin along with council active herbicide + weeding and twice weeding, on reducing the weeds density and biomass as well as increasing the yield and yield components of rice in direct cultivation. 

Discussion:

According to results which were obtained this research and evaluation of yield and yield components are identified that application of herbicide cannot control the weed solitary. This research was showed that application of council active herbicide + weeding and twice weeding cause to reduce the weeds density and biomass as well as increasing the yield and yield components of rice in direct cultivation and also own to elimination of competing species, they improve the crop growth. Therefore, mechanical weeding, which is a non-chemical method of weed management, should be considered as a necessary part of sustainable agriculture.