Performance of Dry Direct Seeded Rice and Weeds on Sesbania Brown Manuring as Compared to Farmers ’ Practice and Chemical Control Method

The research was conducted to study the comparison of farmers’ weed management practice in rice with chemical control and Sesbania co-culture. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications and five different weed management practices. The five treatments were Farmers’ practice (two hand weeding first at 28 DAS and another at 40 DAS), Chemical practice (Bispyribac sodium as post emergence @ 25 g a.i. ha at 25 DAS), Sesbania co-culture (100 kg Sesbania ha and knocking down at 28 DAS), Weed free (Hand removal of weeds at 10 days’ interval) and Weedy check (No weed management). The individual plot size was 5 x 4 m. The Sesbania co-culture and farmers’ practice were found more or less similar performance for all observed parameters but as better as compared to weedy check and chemical treatment. Sesbania co-culture was found less costly than farmers’ practice for weed management. The experiment clearly demonstrated the importance of brown manuring on effective control of weeds in rice field under dry direct seeded rice.


Introduction
Rice is one of the most important cereal crops of the world, and more than half of the world's population depends on rice for their daily sustenance (Chauhan and Johnson, 2011).Various types of changes are being occurred for the rice production system and the shifting from transplanted to direct seeding is one out of those.It is suggested that alternate method of planting i.e.Dry-DSR is gaining popularity regarding its high water use, labor use and energy use efficiencies (Kumar and Ladha, 2011).Thus being cost effective the dry direct seeding method also allows early sowing of wheat.The effective weed management is a major challenge for farmers when adopting dry DSR because of weed flora shifts toward more difficult-tocontrol and competitive grasses and sedges.Higher weed infestation is a major problem in dry-DSR causing major loss to rice production worldwide.The diverse weed populations compete with rice and causing severe yield losses ranging from 12 to 90% (Rao et al., 2007;Singh et al., 2009).S.K. Chaudhary et al. (2018) Int. J. Appl. Sci. Biotechnol. Vol 6(3): 265-269 This paper can be downloaded online at http://ijasbt.org&http://nepjol.info/index.php/IJASBTSesbania co-culture is different from other types of weed management practices.It overcomes the cost associated with manual and herbicidal weeding along with removal of negative impact of chemical herbicide to the soil condition and plant or human life.Sesbania followed by 2,4-D was more effective in suppressing broad leaves and sedges and less effective on grasses (Kumar and Ladha, 2011).Sesbania rostrata is a small semi-aquatic leguminous plant which forms a symbiotic relationship with Gram-negative rhizobia and leads to the formation of nitrogen fixing nodules on both stem and roots.This technology can reduce the weed population by nearly half without any adverse effect on rice yield (Kamboj et al., 2012).Growing of Sesbania as an intercrop with direct seeded rice upto 30 DAS reduced the weed infestation by 30% (Singh, Johnson, Mortimer, &Orrr, 2003).The atmospheric nitrogen fixation and facilitation of crop emergence in areas of soil crust formation are other benefits of this technique in addition to weed suppression (Gopal et al., 2010;Singh et al., 2009).It helps in adding about 15 kg N ha -1 along with smothering of weeds and conserving moisture (Gaire, Dahal, & Amgain, 2013).Thus, the major part is to evaluate its effect on weeds and on the performance of dry direct seeded rice through this experiment.

Materials and Methods
The experiment was carried out at Agronomy Farm of Agriculture and Forestry University (AFU), Rampur, Chitwan.The site is located 9.8 km South-West from Bharatpur, headquarter of Chitwan district.This location is situated at 27 ° 37' N latitude and 84 ° 25'E longitude with the elevation of 256 m above mean sea level (Thapa and Dangol, 1988).Rice variety "US-312" via line sowing and seed of Sesbania rostrata via broadcasting were sown together manually on 7 th of June, 2014.The soil of experimental plot was sandy loam which had medium type of total N (0.2%), available P (46.62 kg ha -1 ) and organic carbon (1.9%) but low in available K (82.8 kg ha -1 ).Five treatments were tested in Randomized Complete Block Design and replicated three times.The treatments were Farmers' practice (two hand weeding first at 28 DAS and another at 40 DAS), Chemical practice (Bispyribac sodium as post emergence @ 25 g.a.i.ha -1 at 25 DAS), Sesbania co-culture (100 kg Sesbania ha -1 and knocking down at 28 DAS), Weed free (hand removal of weeds at 10 days' interval), and Weedy check (No weed management).Each 20 m 2 plot had 20 rows of 5m length, with an inter-row spacing of 0.2 m.The fertilizer was applied in the form of urea, di-ammonium phosphate (DAP), and murate of potash (MOP) whereas the recommended dose of NPK in each experimental plot was 150:80:80 kg ha -1 .One third of nitrogen, full dose of phosphorus and potash were applied as basal dose at final land preparation.Remaining two third dose of Nitrogen was applied at tillering stage and panicle initiation stage in equal split.Zinc sulphate @ 25 kg ha -1 was also applied at final land preparation for correction of zinc deficiency in soil.

Weed Management Practices and Weed Index
The major weeds infesting in dry DSR during experiment were grasses like Cynodon dactylon, Echinochloacolana, Setariaglauca, Paspalum scrobiculatum and Paragrass, broad-leaf weeds like Melochia corchorifolia, Aeschynomene indica, Polygonum hydropiper and Commenlina diffusa and Sedges like Cyperus iria and Fimbristylis miliaceae, etc.The mean weed index was found 24.57% and there recorded significant effect of weed management practices on weed index (Fig. 1).The weed index ranged from lowest (7.27%) in Sesbania co-culture to highest (90.55%) in weedy check.The trend of weed index in farmers' practice and chemical practice was seen increasing respectively followed by weedy check.The weed index in weed free plot was zero because the weeds were completely removed at each 10 days' interval.Weedy check produced higher weed index as compared to other treatments due to presence of invasive number of weeds as never removed from the plot.Sesbania co-culture had lower weed index in comparison of both the farmers' practice and post emergence application of bispyribac sodium @ 25 g a. i. ha -1 .The fast growing Sesbania suppress the population of weed species at early growth stage acting as a cover crop which causes lower weed population in co-cultured plot as corroborates with the findings of Ravisankar et. al. (2008), Joseph et al. (2008), Sharma and Ghosh (2000) and, Angadi et al. (1993).

Effect on Yield Attributes of Dry DSR
Weed free plot had the highest number of effective tillers per square meter (286) which was statistically similar with the two-hand weeding but greater than the other treatments (Table 1).Two hand weeding and the Sesbania co-culture had also statistically similar effective tillers per square meter.The plot treated with bispyribac sodium @ 25 g a. i. ha -1 had been found longer panicle length (25.37 cm) as compared to others and it was statistically similar with all the treatments except weedy check where weedy check had shorter panicle length (22.57cm).In spite of statistically similar patterns except in weedy check, the highest number of grains per panicle (121.77) was found in Sesbania coculture (Table 1).Two hand weeding produced highest TGW (19.05 g) as statistically similar with the result of remaining treatments but was found significantly different with weedy check (16.93 g).TGW was recorded to all the treatments except weedy check (Table 1).Shorter panicle length (22.57cm) was recorded on weedy check plot which might be due to draining of nutrients by weeds.Among all the treatments, the co-culture of Sesbania produced highest panicle weight (2.45 g) which might be due to addition of required nutrients by the activity of Sesbania before and after knocked down.The reason behind the highest number of grains per panicle to Sesbania coculture was the effective suppression of weeds through decomposed leaves of Sesbania acting as mulch which provide more nutrients release and hence absorption by crop during grain filling period.The result agreed with the findings of Gill and Wallia (2014).IRRI (1985) also reported that the Sesbania leaflets degrade rapidly in moist soil and release 50% of their N within four weeks of incorporation.Hasanuzzaman et al. (2008) reported that thousand grain weights remained statistically unchanged in different weed management practices.The weedy check had lowest thousand grain weight (16.93 g) because of the unfavorable environment created by weeds throughout the crop cycle.The lowest sterility percentage was recorded in weed free and statistically similar with other treatments except weedy check.

Effect on Grain Yield, Straw Yield, Above Ground Biomass and Harvest Index of Dry DSR
The highest grain yield (4823.27 kg ha -1 ) was observed in weed free plot as compared to other treatments and statistically similar with the yield of two hand weeding and Sesbania co-culture (Table 2).The weedy check had been found lower grain yield (440.13 kg ha -1 ).The co-culture of rice and Sesbania had produced significantly more grain yield as compared to bispyribac sodium @ 25 g a. i. ha -1 and weedy check.Similarly, the straw yield was found highest (6764.17kg ha -1 ) with weed free plot as statistically similar with all other treatments except weedy check.
The above ground biomass on Sesbania co-culture treatment was found statistically similar with the two hand weeding and weed free plot and also with the application of bispyribac sodium @ 25 g a. i. ha -1 .There were not significant differences among the weed management treatments to the harvesting index.Despite statistically similarity, brown manuring in dry direct seeded rice recorded 4309.13 kg ha -1 which was 4.78 % higher than that of farmers' practice/two hand weeding.The lower yield (440.96 kg ha -1 ) in weedy check might be due to competition from weeds which reduced LAI and allowed less light transmission producing less biosynthate and ultimately low dry matter production.

Conclusion
From the co-culture experiment of Rice and Sesbania, was found rather better than that of the farmer's practice and chemical control practice.It can be concluded that the practice was best because the Sesbania being an aquatic plant helped to suppress most of the weeds and provided the needed nutrients to the crop Rice, and Both the yield and yield attributing characters of rice were found to be better in case of brown manuring than that of farmers practice and chemical practice.In conclusion it can be notify that if this practice of Rice and Sesbania can be continued then it would help in controlling more and more weeds at low cost and will have better yield of rice via providing the adequate nutrients through the Sesbania both before and after it is knocked down at appropriate time.So, it will be better to continue finding of this research in order for the proper yield of rice crops over the farmer's and chemical control practice of weeds in dry direct seeded rice.

Fig. 1 :
Fig. 1: Weed index (%) as influenced by the different weed management practices at Agronomy Farm, AFU Rampur, Chitwan, Nepal, 2014 (mean separated by DMRT with same letter (s) are non-significant at 5% level of significance)

Table 1 :
Yield attributes influenced by the different weed management practices at Agronomy Farm, Note: Mean separated by DMRT and columns represented with same letter (s) are non-significant at 5% level of significance.DAS, days after sowing; ET, effective tillers; PL, panicle length; PW, panicle weight; GPP, grain per panicle; TGW, thousand grain weight; STRL, sterility percentage.

Table 2 :
Grain yield (kg ha -1 ), Straw yield (kg ha -1 ), Above ground biomass (kg ha -1 ) and harvest index as influenced by the different weed management practices at Agronomy Farm, AFU Rampur,