Nitrogen and weed management in direct-seeded rice (Oryza sativa L.)
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Date
2017-09
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Department of Agronomy, BAU, Sabour
Abstract
A field experiment entitled “Nitrogen and weed management in direct-seeded rice (Oryza sativa L.)’’ was conducted during kharif 2015 at Research Farm, Department of Agronomy, Bihar Agricultural University, Sabour, Bhagalpur, Bihar.
Treatments were laid out in split plot design replicated thrice. Three nitrogen splitting, 1/3 at sowing + 1/3 at tillering + 1/3 at panicle initiation (N1), 1/4 at 20 days after sowing + 1/2 at tillering + 1/4 at panicle initiation (N2), 1/3 at 20 days after sowing + 1/3 at tillering + 1/3 at panicle initiation (N3) were kept in main plot and each main plot is sub-divided in five sub-plots having five weed management treatments,viz., weedy (W1), weed free (Three hand weeding at 15, 30 and 45 DAS ) (W2), pendimethalin 1.0 kg a.i. ha-1 PE fb one hand weeding at 30 DAS (W3), pendimethalin 1.0 kg a.i. ha-1 PE fb bispyribac sodium @ 25 g a.i. ha-1 POE (W4), pendimethalin 1.0 kg a.i. ha-1 PE fb ethoxysulfuron @ 18.5 g a.i. ha-1 POE (W5).
Among different nitrogen splitting methods 1/3 at 20 days after sowing + 1/3 at tillering + 1/3 at panicle initiation (N3) resulted the best expression of growth characters and yield attributes at harvest, which was ultimately reflected highest grain yield (36.6 q ha-1), which exhibited statistical parity with N2 treatment and was found significantly superior over N1 treatment which recorded lowest grain yield (35.3 q ha-1). Lowest weed dry weight, highest weed-control efficiency, minimum N uptake by weeds and maximum net returns were recorded with the splits involving 1/3 at 20 days after sowing + 1/3 at tillering + 1/3 at panicle initiation (N3).
Among weed management practices, weed free (Three hand weeding at 15, 30 and 45 DAS) (W2) and pendimethalin 1.0 kg a.i.ha-1 PE fb hand weeding at 30 DAS (W3) were found to be superior in respect of growth characters and yield contributing attributes and final grain yield of rice. The highest N uptake by rice, higher recovery of applied nitrogen, minimum dry weight of weeds, highest weed-control efficiency and minimum depletion of nitrogen by weeds and maximum net returns were recorded with weed free (Three hand weeding at 15, 30 and 45 DAS) (W2) which was at par with pendimethalin 1.0 kg a.i. ha-1 PE fb one hand weeding at 30 DAS (W3).
From the results of the present study, it may be concluded that among nitrogen splitting, application of 1/3 N at 20 days after sowing + 1/3 N at tillering + 1/3 N at panicle initiation in direct seeded rice produced higher growth, yield attributes and net return and among weed management practices, weed free (Three hand weeding at 15, 30 and 45 DAS) and pendimethalin @ 1.0 kg a.i. ha-1 PE fb one hand weeding at 30 DAS were found the best & reflecting higher yield of rice and reduced weed density leads to more weed control efficiency and less weed index, however, pendimethalin @ 1.0 kg a.i. ha-1 PE fb ethoxysulfuron @ 18.5 g a.i. ha-1 POE exhibited maximum B:C ratio. However, the results are of one season. Further experimentation is needed to have the right recommendation of time of nitrogen application and weed management practices for direct seeded rice for a particular agro-climatic situation.
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