Yield and Grain Protein Content of Aromatic Boro Rice ( cv . BRRI dhan 50 ) as Influenced by Integrated Fertilizer and Weed Management

An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during December 2014 to May 2015 to study the effect of integrated fertilizer and weed management on the yield and gain protein content of aromatic Boro rice (cv. BRRI dhan50). The experiment comprised six sets of fertilizer managements. 1. Negative control having no fertilizers and no manures, 2. Recommended dose of inorganic fertilizers (i.e. Urea, TSP, MoP, Gypsum, ZnSO4 @ 250, 120, 120, 100, 10 kg ha, respectively), 3. 50% of recommended dose of inorganic fertilizers + cowdung @ 5 t ha, 4. 75% of recommended dose of inorganic fertilizers + cowdung @ 5 t ha, 5. 50% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha, 6. 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha. Four weed managements 1. Control (no weeding), pre-emergence herbicide, 2. Panida 33 EC + one hand weeding at 35 DAT, 3. Post-emergence herbicide, Granite 240 SC + one hand weeding at 35 DAT and 4. Pre-emergence herbicide, Panida 33 EC + post-emergence herbicide, Granite 240 SC. The highest grain yield (6.40 t ha), grain protein content (7.79%) and benefit cost ratio (2.20) were obtained from 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha with pre-emergence herbicide, Panida 33 EC @ 2.5 l ha + post-emergence herbicide, Granite 240 SC @ 93.70 ml ha while their corresponding lowest values were found in weedy check without fertilization. Weed infestation reduced 58.28% grain yield in control plots due to crop-weed competition compared to plot receiving pre-emergence herbicide + post-emergence herbicide. It can be concluded that 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha combined with pre-emergence herbicide, Panida 33 EC @ 2.5 l ha + post-emergence herbicide, Granite 240 SC @ 93.70 ml ha may be used to obtain the highest grain yield and grain protein content of aromatic Boro rice (cv. BRRI dhan50).


Introduction
Food security is a burning issue of the world at present.Increased rice production can play a vital role to address this issue successfully.Rice is consumed as the staple food in Bangladesh and has been given the highest priority in meeting the demands of its ever-increasing population.It is the most important food crop and a primary food source for more than one-third of world's population (Singh and Singh, 2008).Rice contributes 95% of total food production in Bangladesh.About 77.07% of cropped area of Bangladesh is used for rice production, with annual production of 33.83 million ton from 11.41 million ha of land, which contribute about 19.60% of the country's GDP (BBS, 2013).Aromatic rice contributes a small portion (10%) but an important subgroup of rice production.Total aromatic rice production is about 0.297 million tons in 2013 from 0.158 million ha of land in Bangladesh.In general, aromatic rice is classified by its length, thickness and aroma.However, the price of aromatic rice is 2-3 times higher than that of coarse rice (Chowdhury et al., 1993).Sarkar et al. (2014) reported that Bangladesh has a bright prospect for export of fine rice thereby earning foreign exchange.The yield of fine rice is lower than that of coarse and medium rice varieties.The reason for low yield are mainly associated with selection of improved varieties and judicious fertilizer management especially of organic fertilizers like cowdung, poultry manure and/or their integration with inorganic fertilizers.In recent years, aromatic rice has been introduced to the global market.In Bangladesh, a number of fine rice cultivars are grown viz.Chinisagar, Badshabhog, Kataribhog, Kalizira, Tulsimala, Dulabhog, Basmati, BRRI dhan34, BRRI dhan37 and BRRI dhan38.Currently Bangladesh Rice

Research Article
Research Institute (BRRI) developed a new aromatic rice variety having long grain namely, BRRI dhan50 (Banglamati) for Boro season.
Weeds are major causes of yield loss in upland rice and its control is labour intensive.The climate as well as the edaphic condition of Bangladesh is favourable for the luxuriant growth of weeds.So, the rice crops are usually infested heavily with weeds resulting in the reduction in grain yield.The yield loss due to weed competition are 68-100% in direct seeded Aus rice, 22% in modern Boro rice (Mamun, 1990), 40% in HYV transplant Aman rice (Haque et al., 2012) and 28.16% in aromatic fine rice in Aman season (Zannat et al., 2014).There is no doubt that maximum benefit for costly inputs like fertilizers and pesticides in rice can be fully derived when the crop is kept free from weed infestation.The traditional method of weed control is hand weeding which is very much laborious and time consuming.Mechanical weeding and herbicides are the alternative to hand weeding.Herbicides are effective in controlling weeds alone or in combination with hand weeding.Weed competition at early growth stage can be eliminated through pre-emergence and post-emergence herbicides like Panida, Ronstar 25 EC, Rifit 50 EC, Granite 240 SC and 2, 4-D amine which are good selective, preemergence and post-emergence herbicides (Ahmed et al., 2005).
In all the agricultural systems there is a loss o f plant nutrients.Nutrient mining, depletion of soil organic matter and reduction in soil aggregates have been identified as reasons of yield stagnation or decline in the productivity of crops (Rahman and Yakupitiyage, 2006).Application of cow dung, poul try manure along with other inorganic fertilizers and weed management are the important means in augmenting the yield of crop.The efficient fertilizer and weed management may increase crop yield and at the same time reduces production cost.Therefore, the present study was undertaken to evaluate the effects of integrated fertilizer and weed management on the yield and grain protein content of aromatic Boro rice (cv.BRRI dhan50). [[

Materials and Methods
An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during the period from December 2014 to May 2015 to study the effect of integrated fertilizer and weed management on the growth, yield and quality of aromatic Boro rice (cv.BRRI dhan50).The experimental site belongs to the Sonatola series of the dark grey floodplain soil type under Old Brahmaputra Floodplain Agro-Ecological Zone (AEZ-9).The field was a medium high land with well drained silty-loam texture having pH 6.5 and 1.29% organic matter content.The experiment comprised six sets of fertilizer managements.1. Negative control having no fertilizers and no manures, 2. Recommended dose of inorganic fertilizers (i.e.Urea, TSP, MoP, Gypsum, ZnSO4 @ 250, 120, 120, 100, 10 kg ha-1, respectively), 3. 50% of recommended dose of inorganic fertilizers + cowdung @ 5 t ha-1, 4. 75% of recommended dose of inorganic fertilizers + cowdung @ 5 t ha-1, 5. 50% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha-1, 6. 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha-1.Four weed managements viz.control (no weeding), preemergence herbicide, Panida 33 EC + one hand weeding at 35 DAT, post-emergence herbicide, Granite 240 SC + one hand weeding at 35 DAT, pre-emergence herbicide, Panida 33 EC + post-emergence herbicide, Granite 240 SC.The experiment was laid out in a factorial randomized complete block design with three replications.
The nursery beds were puddled with country plough, cleaned and levelled with ladder.Then the sprouted seeds were sown in the nursery beds on 07 December 2014.At the time of final land preparation, respective unit plots were amended with organic and inorganic fertilizers according to treatment specification.Urea was top dressed in three equal splits at 15, 35 and 55 DAT (panicle initiation stage).Full dose of triple super phosphate, muriate of potash, gypsum and zinc sulphate were applied at final land preparation.Thirty five-day old seedlings were transplanted on 10 January 2015 in the well puddled plot.Three seedlings were transplanted hill -1 with a spacing of 25 cm × 15 cm.The weed density and biomass of infesting weeds were recorded at 60 DAT with the help of a plant quadrate measuring 1 m × 1 m from each plot.The collected weeds were dried in an electric oven for 72 hours at a temperature of 85 ± 5°C.After drying, the dry weight of each plot was recorded by an electrical balance.Prior to harvest, five hills plot -1 were randomly selected excluding border hills and central 1 m 2 area from each unit plot for recording data on yield components.The crop of central 1 m 2 harvest area of each plot was harvested at full maturity when 85% of the grain became golden yellow in color on 07 May 2015.The harvested crop of each plot was separately bundled, properly tagged and then threshed.Grains were then cleaned and sun dried to a moisture content of 14%.Finally the grain and straw yields plot -1 were recorded and converted into t ha -1 .Estimation of protein (%) in grains was done by Micro-Kjeldahl Method (AOAC, 1984).Collected data were analyzed following the analysis of variance (ANOVA) technique and mean differences were adjudged by Duncan's Multiple Range Test (DMRT) (Gomez and Gomez, 1984).In a column, figures with same letter(s) or without letter do not differ significantly whereas figures with dissimilar letter differ significantly (as per DMRT).** =Significant at 1% level of probability NS = Non-significant F0 = Control (no fertilizer and no manure) F1 = Recommended dose of inorganic fertilizer (Urea, TSP, MoP, Gypsum, ZnSO4 @ 250, 120, 120, 100, 10 kg ha -1 , respectively).F2 = 50% of recommended dose of inorganic fertilizer + cowdung @ 5 t ha -1 F3 = 75% of recommended dose of inorganic fertilizer + cowdung @ 5 t ha -1 F4 = 50% of recommended dose of inorganic fertilizer + poultry manure @ 2.5 t ha -1 F5 = 75% of recommended dose of inorganic fertilizer + poultry manure @ 2.5 t ha -1 In a column, figures with same letter(s) or without letter do not differ significantly whereas figures with dissimilar letter differ significantly (as per DMRT).** = Significant at 1% level of probability.* = Significant at 5% level of probability.NS = Non-significant.W0 = control (unweeded) W1 = pre-emergence herbicide, Panida 33 EC @ 2.5 l ha -1 + one hand weeding at 35 days after transplanting (DAT) W2 = post-emergence herbicide, Granite 240 SC @ 93.70 ml ha -1 + one hand weeding at 35 days after transplanting (DAT) W3 = pre-emergence herbicide, Panida 33 EC @ 2.5 l ha -1 + post-emergence herbicide, Granite 240 SC @ 93.70 ml ha -1 .In a column, figures with same letter(s) or without letter do not differ significantly whereas figures with dissimilar letter differ significantly (as per DMRT).** = Significant at 1% level of probability, * = Significant at 5% level of probability, NS = Non-significant F0 = Control, F1 = Recommended dose of inorganic fertilizer ( Urea, TSP, MoP, Gypsum, ZnSO4 @ 250, 120, 120, 100, 10 kg ha -1 ,respectively), F2 = 50% of recommended dose of inorganic fertilizer + cowdung @ 5 t ha -1 , F3 = 75% of recommended dose of inorganic fertilizer + cowdung @ 5 t ha -1 , F4 = 50% of recommended dose of inorganic fertilizer + poultry manure @ 2.5 t ha -1 , F5 = 75% of recommended dose of inorganic fertilizer + poultry manure @ 2.5 t ha -1 , W0 = control (unweeded), W1 = pre-emergence herbicide (Panida 33 EC) + one hand weeding at 35 DAT, W2 = post-emergence herbicide (Granite 240 SC) + one hand weeding at 35 DAT, W3 = pre-emergence herbicide (Panida 33 EC) + post-emergence herbicide herbicide (Granite 240 SC).

Effect of Integrated Fertilizer Management
Table 1 shows that crop-characters, yield-contributing characters and yield were significantly influenced by fertilizer management.The application of 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha -1 showed superiority in terms of the highest plant height (82.75 cm).Number of total tillers hill -1 (18.90), number of effective tillers hill -1 (16.36), panicle length (22.51 cm), number of grains panicle -1 (132.4),grain yield (5.56 t ha -1 ), straw yield (6.56 t ha -1 ) and harvest index (47.05%).The second highest of the same parameters was found in 75% of recommended dose of inorganic fertilizers + cowdung @ 5 t ha -1 , which was statistically at par with 50% of recommended dose of inorganic fertilizers + cowdung @ 5 t ha -1 .Pal et al. (2016) found that number of grains panicle -1 increased with combined application of organic and inorganic fertilizers.Roy et al. (2015) reported that integrated nutrient can increase grain yield of Boro rice.
Probably combined application of inorganic fertilizers withmanure provided adequate nutrients to the plants and exhibited the best performance due to absorption of more nutrients and moisture.These results are in agreement with that of Kabir et al. (2004) who found differences in yield and yield contributing characters increased due to different levels of fertilizer management.The treatment control (no fertilizer and manure) gave the lowest values for the same parameters due to lack of proper nutrient uptake.The lowest number of non-effective tillers hill -1 (2.15) was found from the treatment 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha -1 .The highest grain protein content (7.69%) was found when fertilized with 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha -1 , which was statistically identical to the grain protein content (7.49%) obtained from 75% of recommended dose of inorganic fertilizers + cowdung @ 5 t ha -1 .This might be due to availability and uptake of adequate nitrogen from the soil.The lowest grain protein content (4.27%) was observed in control (no fertilizer and no manure).Biswas et al. (2016) and Sarkar et al. (2014) reported the similar increasing trend of grain protein content in case of aromatic fine rice.Grain protein content increased significantly at higher amount of nitrogen application was reported elsewhere (Chandel et al., 2010 andRay et al., 2015).

Effect of Weed Management
Weed management influenced significantly crop characters, yield contributing characters and yield (Table 1).The tallest plant (81.76 cm), number of total tillers hill -1 (18.96), number of effective tillers hill -1 (16.49), panicle length (22.48 cm), number of grains panicle -1 (131.7),grain yield (5.61 t ha -1 ), straw yield (6.41 t ha -1 ) and harvest index (42.26%)were recorded in pre-emergence herbicide, Panida 33 EC @ 2.5 l ha -1 + post-emergence herbicide, Granite 240 SC @ 93.70 ml ha -1 .The second highest of the same parameters was found in pre-emergence herbicide, Panida 33 EC + one hand weeding at 35 DAT, which was statistically identical with post-emergence herbicide, Granite 240 SC + one hand weeding at 35 DAT.The treatment control (unweeded) gave the lowest values for the same parameters under unweeded condition.Weed competed with the crop for nutrition, water, air, sunlight and space thus reducing yield.The grain yield reduced 58.28% in control plots followed by (7.31 %) pre-emergence herbicide, Panida 33 EC @ 2.5 l ha -1 + one hand weeding at 35 DAT over pre-emergence herbicide, Panida 33 EC @ 2.5 l ha -1 + post-emergence herbicide, Granite 240 SC @ 93.70 ml ha -1 .The increased yield in weeded crops was contributed by higher number of effective tillers hill -1 and higher number of grains panicle -1 over no weeding treatment.This might be due to the fact that the weeding kept the land clean and soil was well aerated which facilitated the crop for better absorption of nutrients, moisture and solar radiation for higher yield.Effective weed management enhanced production of effective tillers hill - 1 and grains panicle -1 , which ultimately increased grain yield of rice.Zannat et al. (2014) found that weed infestation reduced 28.16% yield in control plots compared to three weedings in aromatic fine rice.

Effect of Interaction between Integrated Fertilizer and Weed Management
The interaction effect of integrated fertilizer and weed management was significant on yield and yield contributing characters of aromatic Boro rice (cv.BRRI dhan50) (Table 3).The highest number of total tillers hill -1 (21.30), number of effective tillers hill -1 (19.50), panicle length (22.65cm), grain yield (6.40 t ha -1 ) and straw yield (8.22 t ha -1 ) were recorded in the interaction between 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha -1 with pre-emergence herbicide, Panida 33 EC @ 2.5 l ha -1 + post-emergence herbicide, Granite 240 SC @ 93.70 ml ha - 1 .The lowest values of these parameters were found in the interaction between control fertilizers under unweeded condition, which was statistically identical to the treatment 50% of recommended dose of inorganic fertilizer + cowdung @ 5 t ha -1 with unweeded.The highest harvest index (51.06%)was found in the interaction between 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha -1 with pre-emergence herbicide, Panida 33 EC.The highest grain protein content (7.79%) was recorded in the interaction of 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha -1 with preemergence herbicide, Panida 33 EC @ 2.5 l ha -1 + postemergence herbicide, Granite 240 SC @ 93.70 ml ha -1 while the lowest grain protein content (4.37%) was observed in control fertilizer under unweeded condition.Application of inorganic fertilizer with organic manure increased protein content ability of fine rice was reported elsewhere (Sarkar et al., 2014;Pal et al., 2016 andBiswas et al., 2016).As like as grain yield and protein content the highest benefit cost ratio (2.20) was found in the interaction of 75% of recommended dose of inorganic fertilizers + poultry manure @ 2.5 t ha -1 with pre-emergence herbicide, Panida 33 EC @ 2.5 l ha -1 + post-emergence herbicide, Granite 240 SC @ 93.70 ml ha -1 .

Relationship between Weed Biomas Production at 60 DAT and Grain Yield
A negative relationship between weed dry matter production and grain yield of aromatic Boro rice (cv.BRRI dhan50) was observed, which indicated that higher the weed dry matter production lower the grain yield.The response of weed dry matter production to the grain yield of rice followed a linear negative relationship that could be adequately described by regression equation.The regression equation indicates that an increase in weed dry matter production would led to a decrease in the grain yield of rice (Fig. 1).

Conclusion
From the present study, it can be concluded that application of 75% is the recommended dose of inorganic fertilizers and poultry manure @ 2.5 t ha -1 along with pre-emergence herbicide.Panida 33 EC @ 2.5 l ha -1 + post-emergence herbicide, Granite 240 SC @ 93.70 ml ha -1 may be used to obtain the highest grain yield and grain protein content of aromatic Boro rice (cv.BRRI dhan50).

Table 1 .
Effect of integrated fertilizer management on yield and yield contributing characters of aromatic Boro rice (cv.BRRI dhan50)

Fig 1 :
Fig 1: Relationship between weed dry matter production at 60 DAT and grain yield of aromatic Boro rice (cv.BRRI dhan50)

Table 2 :
Effect of weed management on yield and yield contributing characters of aromatic Boro rice (cv.BRRI dhan50)

Table 3 :
Effect of interaction between integrated fertilizer and weed management on yield and yield contributing characters of aromatic Boro rice (cv.BRRI dhan50)