EFFECT OF NITROGEN AND PHOSPHORUS ON THE GROWTH AND YIELD PERFORMANCE OF SOYBEAN Mst

Nitrogen Phosphorus Production Soybean The experiment was conducted at the Agronomy Field Laboratory of Bangladesh Agricultural University, Mymensingh to study the effects of nitrogen and phosphorus on the performance of soybean. Three levels of nitrogen (0, 25 and 40 kg N ha-1) and four levels of phosphorus (0, 18, 36 and 54 kg P ha-1) were considered as treatment for the experiment. Soybean responded remarkably to the added nitrogenous and phosphatic fertilizers as the crop characters were significantly influenced by different levels of nitrogen and phosphorus. Significant effect on number of branches and seeds plant-1, plant height, number of filled pods plant-1, weight of seeds plant-1, dry weight of plant, stover weight plant-1, 1000-seed weight, seed and stover yield were obtained from the combined application of 25 kg N with 54 kg P ha-1.

The experiment was conducted at the Agronomy Field Laboratory of Bangladesh Agricultural University, Mymensingh to study the effects of nitrogen and phosphorus on the performance of soybean.Three levels of nitrogen (0, 25 and 40 kg N ha -1 ) and four levels of phosphorus (0, 18, 36 and 54 kg P ha -1 ) were considered as treatment for the experiment.Soybean responded remarkably to the added nitrogenous and phosphatic fertilizers as the crop characters were significantly influenced by different levels of nitrogen and phosphorus.Significant effect on number of branches and seeds plant -1 , plant height, number of filled pods plant -1 , weight of seeds plant -1 , dry weight of plant, stover weight plant -1 , 1000-seed weight, seed and stover yield were obtained from the combined application of 25 kg N with 54 kg P ha -1 .

INTRODUCTION
Soybean (Glycine max L. Merril) ranks first as an oilseed crop of the world.It has a tremendous value in agriculture as a good source of high quality plant protein and vegetable oils in one hand and nitrogen fixing ability on the other.It belongs to the family Leguminosae, sub family Papilionaceae.Soybean is quite wide spread in different regions of the world and grows well from the tropics to the temperate zones with greater production in the United States, Brazil, China, Mexico, Indonesia and Argentina.The world production of soybean as estimated in 2008 was 231.27 million ton from an area of 96.47 million hectares (FAO, 2009).For its nutritive value soybean has been called miracle golden bean, the golden nugget, the nugget of nutrition etc. soybean being a good source of protein, unsaturated fatty acids, minerals like Ca and P and vitamin A, B, C and D can meet up different nutritional needs of human being (USDA, 2009).
Prospects of soybean farming in Bangladesh is bright as it can successfully be grown under a wide range of climatic and edaphic conditions and cultivated throughout the year in Bangladesh (Rahman, 1982).Soybean helps to improve the soil by fixing the atmospheric nitrogen through Rhizobium bacteria.Steward (1966) observed that the soybean plants could fix 94 kg nitrogen ha -1 in soil in a season.In Bangladesh the area under soybean cultivation is about 5000 ha with a production of 4000 ton & the yield ranges from 1.50 to2.30tha -1 (BARI, 2005).The lower yield of soybean at farmer's level is mainly attributed to the lack of improved agronomic management practices of which judicious fertilizer application is an important determinant for better yield of soybean.Among the nutrients, nitrogen is a major essential plant nutrient element.It has the quickest and most pronounced effect on plant growth and yield of crops.It tends primarily to encourage above ground vegetative growth and to impart deep green colour to the leaves.In all plants, nitrogen governs a considerable degree of utilization of potassium, phosphorus and other nutrients.Plants receiving insufficient nitrogen are stunted in growth with restricted root systems.The leaves turn yellow or yellowish green and tend to drop off.
Phosphorus can play an important role in seed yield as it is one of the limiting plant nutrients for production of soybean (Rao et al., 1995).Its uptake and utilization by soybean is essential for ensuring proper growth & improving yield and quality of the crop.It influences the growth of roots, helps uptake of more nutrients and nodule formation, balances the nitrogen deficiency in soil and assists in seed maturation.Thus, it is needed to find out proper amount of nitrogen and phosphorus required for achieving better yield of soybean.In view of the facts stated above, a field experiment was conducted to evaluate the effect of different levels of nitrogen and phosphorus and their interaction on the yield of soybean.

MATERIALS AND METHODS
The experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during 5 January to 20 April, 2009 to study the effects of rate of nitrogen and phosphorus on the yield of soybean.The experimental field was a high land having sandy loam soil with pH 6.9.The initial soil (0-15 cm depth) test result showed that the soil contained 0.058% total N, 0.463% organic matter, 23 ppm available P, 5.0 ppm available S and 0.13 ppm exchangeable K. Three levels of nitrogen (0, 25 and 40 kg N ha -1 ) and four levels of phosphorus (0, 18, 36 and 54 kg P ha -1 ) were considered as treatment for the experiment.The experiment was laid out in a randomized complete block design with three replications.Urea & TSP were used as the source of N & P, respectively.
Half of the N and whole of P were applied as basal on 5 January 2009 as per treatment in the individual plots.Besides, MoP and gypsum were applied @ 120 and 115 kg ha -1 , respectively on the same date.Inoculum @ 50 g kg -1 of seed was mixed with seed prior to sowing.The remaining half of the N was top dressed at 25 days after sowing.Weeding followed by thinning was done simultaneously twice at 21 and 45 days after sowing.Irrigation was done simultaneously twice on 25 and 55 days after sowing.Sumithion 50 EC @ 3 m1L -1 and Dimethion 40 EC @ 2 mlL -1 were sprayed to control leaf roller and hairy caterpillar.The crop was harvested on 20 April 2009 at full maturity.The collected data were analyzed statistically following the ANOVA technique and the mean differences were adjudged as per Duncan's Multiple Range Test (Gomez and Gomez, 1984).

RESULTS AND DISCUSSION
The results of the present experiment have been presented and discussed in the Table 1, 2 and 3.

Effect of nitrogen
Nitrogen had significant effect on yield and yield contributing characters of soybean (Table 1).Plant height was significantly influenced by nitrogen.Crop grown with 40 kg N ha -1 produced the tallest plant (34.18 cm) and with 0 kg N ha -1 treatment produced the shortest plants (30.01cm).The highest dry matter weight plant -1 (17.89g), number of seeds pod -1 (1.94), number of seeds plant -1 (94.93), seeds weight plant -1 (3.41g), 1000 seed weight (111.26g),number of filled pods plant -1 (47.59) but lowest empty pods plant -1 (2.42) were observed with 25 kg N ha -1 followed by 40 kg N ha -1 application whereas, the crops showed poor performance with no nitrogen (0 kg N ha -1 ) application.Among the treatments, 25 kg N ha -1 produced highest weight of 1000 seed (120.24g) which was statistically significant than other treatments.The lowest weight of 1000 seed (111.26g) was obtained with control treatment and subsequently lowers than others.The present result supports the report of Raju and Verma (1984) as they observed that increased N fertilizer has an advantageous role on 1000 seed yield increment.The highest seed yield (1.95 t ha -1 ) was obtained in 25 kg N ha -1 and the lowest (1.41 tha -1 ) was recorded in control (0 kg N ha -1 ) treatment.The highest seed yield in 25 kg N ha -1 might have resulted due to cumulative favourable effects of number of seeds plant -1 , weight of seeds plant -1 and 1000 seed weight.The result obtained is in agreement with the findings of Singh et al. (1992) as he reported yield of soybean increased with the increased rate of N fertilizer rate.The stover yield followed the similar trend as observed for seed yield.Leelavathi et al. (1991) obtained the similar findings in case of stover yield.

Effect of phosphorus
Phosphorus had tremendous effect on soybean (Table 2).The yield and yield contributing characters showed better response with the increased level of phosphorus.The tallest plant (34.26 cm), maximum dry matter weight plant -1 (18.89 g) and maximum number of branches plant -1 (3.37) was recorded with 54 kg P ha -1 which was significantly highest than those of other treatments.The number of filled pods plant -1 (54.49) was the highest in 54 kg P ha -1 which was significantly highest than those of other treatments.The lowest number of filled pods plant -1 was observed from 0 kg P ha -1 .The present results supports the reports of Singh and Bajpai (1990) who observed that increasing phosphorus rate increased the number of pods plant -1 .Among the treatments 0 kg P ha -1 produced the highest number of empty pods (3.98) which was statistically significant with other treatments and the lowest (2.16) was found in 54 kg P ha -1 .Islam et al. (2004) reported that the percentage of empty pods decreased with the increase of phosphorus application.Number of seeds pod -1 was escalated with the increased dose of phosphorus.Tomar et al. (2004) observed that number of seeds pod -1 increased with the increase of phosphorus application.Similar trend was found in case of seeds plant -1 .The obtained result is in agreement with the findings of Islam et al. (2004).Maximum weight of seed plant -1 (3.49g) was observed in 54 kg P ha -1 .The highest weight of stover plant -1 (9.07 g) and 1000-seed weight (122.2g) was observed in 54 kg P ha -1 which were statistically significant than those of other treatments whereas lowest from control (0 kg P ha -1 ) treatment.Significantly higher seed yield (2.09 t ha -1 ) was obtained in 54 kg P ha -1 and the lower (1.30t ha -1 ) was recorded in control (0 kg P ha -1 ).The highest seed yield in 54 kg P ha -1 might have resulted due to cumulative effects of the number of seeds pod -1 , number of seed plant -1 and weight of seeds plant -1 .The present results support the reports of Syafruddin et al. (1990) who observed that seed yield was highest 90 kg P ha -1 .The stover yield followed the similar trend as observed in seed yield.Tomar et al. (2004) reported higher trend of stover yield with higher dose of P fertilizer.In a column figures with same letter or without letter do not differ significantly whereas figures with dissimilar letter differ significantly (as per DMRT) Sx = Sample standard deviation; * = Indicates significant at 5% level of probability; ** = Indicates significant at 1% level of probability; NS = Indicates not significant In a column figures with same letter or without letter do not differ significantly whereas figures with dissimilar letter differ significantly (as per DMRT) Sx = Sample standard deviation; * = Indicates Significant at 5% level of probability; ** = Indicates Significant at 1% level of probability; NS = Indicates Not significant.In a column figures with same letter or without letter do not differ significantly whereas figures with dissimilar letter differ significantly (as per DMRT) Sx = Sample standard deviation; * = Indicates significant at 5% level of probability; ** = Indicates significant at 1% level of probability; NS = Indicates not significant.

Table 1 .
Effect of nitrogen on the yield and related crop characters of soybean var.Shohag

Table 2 .
Effect of phosphorus on the yield and related crop characters of soybean var.Shohag

Table 3 .
Interaction effect of nitrogen and phosphorus on the yield and related crop characters of soybean var.Shohag