Yield and Nutrient Uptake by Soybean as Influenced by Phosphorus and Sulphur Nutrition in Typic Haplustept

Field experiment was conducted on Typic Haplustept at Instructional Farm of Rajasthan College of Agriculture, Udaipur during kharif 2012 to assess the effect of phosphorus and sulphur fertilization on yield and nutrient uptake by soybean [ Glycine max (L.) Merrill]. The experiment was laid out in factorial randomized block design with three replication and consisted four levels of phosphorus (0, 20, 40 and 60 kg P 2 O 5 ha -1 ) and four levels of sulphur (0, 15, 30 and 45 kg S ha -1 ). The results revealed that increasing the levels of phosphorus and sulphur significantly increased the grain and haulm yield over the control. The uptake of N, P, K, S, Fe, Mn, Cu and Zn were significantly higher by grain and haulm over the control. The results of the experiment indicated that application of 60 kg P 2 O 5 ha -1 and 30 kg S ha -1 had recorded significant uptake of N, P, K, S, Fe, Mn, Cu and Zn by grain and haulm of soybean, which also influenced the yield.

Soybean, being a highly nutrient exhaustive oil seed legume, it requires higher amount of nutrients particularly, P and S for higher productivity (Hasan, 1994).Phosphorus is a key element involved in various functions in the growth and metabolism of soybean.It is frequently a major limiting nutrient for plant growth in most of the Indian soils.Phosphorus is also an important constituent of major biological products in plants itself and plays a key role in the balance nutrition of the crops.Sulphur plays an outstanding role in the synthesis of sulphur containing essential amino acids like cystine, *Corresponding author email : ramharim@gmail.comcystenine and methionine; vitamins; co-enzyme-A and metabolism of carbohydrates, protein, fats, chlorophyll formation.It also takes part in Nmetabolism and promotes nodulation for N2-fixation in legumes.Sulphur gives rise to bold seeds in oil seed crops.Soybean is a sulphur loving plant, like any other oilseed crop.The low productivity of soybean may be ascribed to many reasons but, inadequate and imbalanced fertilization plays an important role.Therefore, the present study was undertaken to evaluate the effect of phosphorus and sulphur on the production potential and nutrient uptake by soybean.

Materials and Methods
A field experiment was conducted during kharif 2012 at the Instructional Farm of Rajasthan College of Agriculture, Udaipur.The experimental soil was sandy clay loam in texture, slightly alkaline (pH 7.9), organic carbon (0.67 %), medium with respect to available nitrogen, phosphorus and high in potassium (281.30, 15.75 and 341.50 kg ha -1 , respectively).The sulphur content in the soil was 8.90 mg kg -1 .Available Fe, Mn, Cu and Zn content were 4.21, 5.43, 2.89 and 2.67 mg kg -1 , respectively.The treatments consisted of four levels of phosphorus (0, 20, 40 and 60 kg P 2 O 5 ha ) in integration with four levels of sulphur (0, 15, 30 and 45 kg S ha -1 ) tested in a factorial randomized block design and replicated thrice.A promising variety of soybean, RKS-24 was sown manually in furrows maintaining optimum plant spacing of 30 x10 cm.Phosphorus and sulphur were applied through di ammonium phosphate and gypsum, respectively.All the recommended cultural operations other than the treatments were practiced to raise the crop.For determination of uptake of N, P, K, Fe, Mn, Cu and Zn kg ha -1 ) and haulm yield (3407.34 kg ha -1 ) were recorded for plots having treatment, 60 kg P O ha -1 2 5 by soybean, soil and plant samples in different followed by the application of 40 and 20 kg P O ha -1 .
2 5 treatments were collected and subjected to analysis.Grain and haulm yield were recorded after manual threshing and expressed as kg ha -1 .

Yield of soybean
Effect of phosphorus and sulphur application on grain and haulm yield of soybean was significantly influenced by different levels of phosphorus and sulphur (Table 1).The highest grain yield (1901.44 Whereas, the highest grain yield (1868.64 kg ha -1 ) and haulm yield (3370.64 kg ha -1 ) were recorded under treatment 45 kg S ha -1 but, in case of grain yield; it was at par with the application of 30 kg S ha -1 .Application of phosphorus (20, 40 and 60 kg ha -1 ) and sulphur (15, 30 and 45 kg ha -1 ) resulted in 13.0, 23.8, 34.0% and 10.4, 21.3, and 28.8% increase in grain yield over the control, respectively.Increase in haulm yield was 12.0, 22.4, 32.0 and 10.5, 21.5, 29.1% over the control, respectively under application of phosphorus (20, 40 and 60 kg ha -1 ) and sulphur (15, 30 and 45 kg ha -1 ).With increased supply of sulphur, the process of tissue differentiation from somatic to reproductive, meristematic activity and development might have increased, resulting in an increase in the number and size of leaves (Mengel and Kirkby, 1987).

Table 2. Effect of phosphorus and sulphur on haulm yield and nutrient uptake by haulm of bean
Treatments Haulm yield Macro-nutrient uptake(kg ha -1 ) Micro-nutrient uptake(g ha -1 ) P-Levels (kg ha The interaction effect of phosphorus and sulphur also influenced the grain and haulm yield of soybean.The combined application of P and S, further enhanced grain and haulm yield of soybean (Table 3).The maximum grain and haulm yield (2141.70 kg ha -1 ) and (3847.76kg ha -1 ) were recorded at the highest level of phosphorus (60 kg haulm yield was 71.3 and 69.2% due to the ha -1 ) along with sulphur 30 kg ha -1 , which was found combined application of 60 kg P 2 O 5 ha -1 and 30 kg S to be statistically at par with highest level of ha -1 over control, respectively.phosphorus and sulphur (60 kg P O ha -1 + 45 kg S -1 2 5 The synergistic effect of P and S may be due to ha ).Whereas, the lowest grain and haulm yield of soybean (1520.01kg ha -1 ) and (2273 kg ha -1 ) were recorded when phosphorus and sulphur (P0S0) were not applied.The magnitude of increase in grain and the utilization of higher quantities of nutrients through their well developed root system and nodules, which might have resulted in better growth

Table 4. Interaction effect of P and S on total uptake of phosphorus, sulphur and micro-nutrients by soybean
Treatment P uptake S uptake Fe uptake Mn uptake Cu uptake Zn uptake (kg ha -1 ) (kg ha -1 ) (g ha -1 ) (g ha -1 ) (g ha -1 ) (g ha -1 ) T

Macro-nutrient uptake
It is evident from the data on Table 1 and 2 that the nutrient uptake by soybean grain and haulm increased significantly due to application of phosphorus and sulphur.The maximum uptake of macro and micro nutrients were recorded with the application of 60 kg P ha -1 and 30 kg S ha -1 .Application of phosphorus and sulphur either alone or in combination significantly increased N, P, K, and S uptake by soybean grain and haulm over the control; while, the lowest N, P, K, and S uptake were observed under the control plot.Phosphorus applied at the rate of 60 kg P2O5 ha resulted in significant uptake of N by 40.6 and 39.5% over the control by soybean grain and haulm, respectively; whereas, 36.5 and 38.2% increase in N uptake was observed in grain and haulm due to application of 45 kg S ha -1 , respectively.
Significantly increased trend of P uptake in grain and haulm was recorded with increased levels of phosphorus upto 60 kg P2O5 ha , resulting in 42.0 and 38.6% increased P uptake over control, grain over control, respectively.Maximum Fe uptake respectively.Minimum P uptake in grain as well as was recorded with application of 60 kg P 2 O 5 ha -1 haulm was noticed in control.Results indicated that application of sulphur significantly increased P uptake in grain and haulm with successive levels of and 30 kg S ha -1 followed by 40 kg P O ha -1 and 45 kg S ha -1 .The P and S interaction was also significant with the highest total Fe uptake (290.25 sulphur upto 45 kg S ha -1 (Table 1), resulting in 36.1 g ha -1 ) observed in P S (60 kg P O & 30 kg S ha -1 ), 4 3 2 5 and 43.2% increased P uptake over the control, respectively.
which was statistically at par with P 4 S 4 (60 kg P 2 O 5 and 45 kg S ha -1 ).Minimum Fe uptake (172.60 g ha -1 ) Application of 2, 40 and 60 kg P O ha -1 showed was recorded in P0S0.Due to acidifying effect of S 2 5 oxidation, the availability and uptake of Fe increased a significant increase of 16.9, 28.7 and 39.6% potassium uptake in grain and 13.2, 25.1 and 36.4% in haulm over the control, respectively.Sulphur application (15, 30 and 45 kg ha -1 ) resulted in increase of K uptake by 13.5, 25.0 and 33.6% in grain and 10.8, 26.7 and 35.7% in haulm over the control, respectively.Uptake of sulphur by grain and haulm showed a significant variation with the application of different levels of phosphorus and sulphur (Table 1).Sulphur uptake significantly increased with application of 60 kg P O ha -1 in grain and haulm by 55.2 and 49.2% over the control, respectively.Increasing sulphur levels upto 45 kg S ha -1 resulted an increase in S uptake in grain and haulm by 48.1 and 45.0% over the control.The highest S uptake was found, when sulphur was applied @ 45 kg ha -1 and the lowest from no sulphur application.The above results revealed that the increase in S dose, increase the uptake of sulphur due to high S content, which and resulted in higher grain yield.Among S and P interactions, the highest total P (21.16 kg ha -1 ) and (Hilal et al. 1990).Sulphur application resulted in increased Fe uptake, as reported by Malewar and Ismail (1997).They observed that application of 80 mg S/kg increased Fe availability by 49%.They concluded that there existed a close relationship between Fe and S metabolism in plants.Similar results were also reported by Togay et al. (2008) and Islam et al. (2009) in chickpea.
Application of phosphorus (20, 40 and 60 kg ha -1 ) had significant effect on Mn uptake in grain by 19.2, 36.9 and 48.7% increase over control.Sulphur (15, 30 and 45 kg S ha -1 ) application resulted in 19.8, 41.8 and 55.4% increase in Mn uptake by grain (Table 2).Maximum uptake was recorded with application of 60 kg ha -1 and 45 kg S ha -1 .Almost similar trend was observed regarding Mn uptake by haulm (Table 2).Havlen et al. (2007) reported that availability of Mn increased due to application of acid (NH +) forming fertilizers.Modaihsh et al. (1989) S uptake (7.90 kg ha -1 ) were recorded in P S (60 kg 4 3 2 and Hilal et al. (1990) reported that S application P O ha -1 + 30 kg S ha -1 ), which was statistically at par with P S (60 kg P O ha -1 + 45 kg S ha -1 ).On the other hand, the minimum total uptake of P (11.34 kg ha -1 ) and S (3.80 kg ha -1 ) were recorded in P S These results are in agreement with those of Ganeshamurthy (1996), who reported that application of sulphur significantly increased the S uptake.Similar result was reported by Chand et al. (1997) in mustard.Nimje (2003) also reported an increase in the nutrient uptake with the increase in fertility levels.

Micro-nutrient uptake
Phosphorus (20, 40 and 60 kg ha -1 ) and sulphur (15, 30 and 45 kg ha -1 ) application resulted in 13.4, 24.8 and 35.8%; 10.3, 21.8 and 32.0%Fe uptake by increased Mn availability in soil.Possibility of increase in Mn uptake by soybean might be due to increased root growth and high availability of Mn in soil.Similar results regarding Mn uptake influenced by P and S was also reported by Togay et al. (2008) and Islam et al. (2009) in chickpea.
Phosphorus (20, 40 and 60 kg ha -1 ) and sulphur (15, 30 and 45 kg ha -1 ) application resulted in increased Cu uptake by grain over control.Application of higher level of phosphorus (60 kg ha -1 ) had significant effect in Cu uptake by haulm over control; but, it showed non significant effect over its lower dose (20 and 40 kg ha -1 ); while, Cu uptake significantly increased with increase in the level of sulphur application upto 45 kg S ha -1 .Modaihsh et 0.
-1 -1 al. (1989) observed that S application significantly increased the availability of Cu in soil.Increase in Cu uptake with P and S application might be due to increased root growth, which would have resulted in better exploration of soil volume.These results were in conformity with the findings of Togay et al. (2008) and Islam et al. (2009), who reported an increase in Cu uptake by chickpea with the application of P and S.
(20 and 40 Kg P2O5 ha ).Due to acidifying effect of S oxidation, the availability of Zn increased (Hilal et al. 1990).Application of P and S resulting in increased uptake of Zn by plant might be due to their increased availability in soil.The hypothesis that P application resulted in the formation of insoluble zinc phosphate is not true and many workers have shown that P application has no effect on available Zn in soil (Tandon, 2001).Increase in zinc uptake in response to S application has been reported earlier (Babhulkar et al. 2000) due to increased root surface area resulting from better growth due to S supply.