​Effect of Organic and Inorganic Sources of Nutrients on Growth, Yield Attributes and Nutrient Uptake of Soybean in Vertisols of Rajasthan

Soybean (Glycine max L.) belongs to family Leguminaceae or Fabaceae and Sub- family Papilionaceae. It is famous as the ‘golden bean’ of the 20^th century which is also used as food beverage. It is containing 38-42% protein, 20-22% edible oil in the grain and 26% carbohydrates, 4% minerals, 2% phospholipids, rich in poly unsaturated fatty acid, vitamin C, 5-6% crude fibre and lysine amino acid. Soybean being a highly nutrient exhaustive legume requires higher amount of nutrients, particularly phosphorous and potassium for its optimum production. Estimated production of soybean in world is 364.33 million tonnes and area is 127.19 million hectares whereas in India it was 12.10 million tonnes production from an area of 10.80 million hectares and in Rajasthan is 1.16 million tonnes production and area is 0.93 million hectares (Anonymous, 2018).
              
Consecutive use of organic manures, biofertilizers and inorganic fertilizers to archives sustained crop production and maintain the soil health is the basic need of the hour. INM is the best approach for better utilization of resources and to produce crops with less expenditure. Organic manures are used to supply both macro and micronutrients and sustain amount of humic substances particularly humic and fulvic acid that helps to maintain soil reaction. Organic sources of nutrients are derived from animal, human and agriculture wastes (e.g. composting and crop residues). Vermicompost is rich organic manure consist of macro and micronutrients, plant growth promoting substances, beneficial micro-organisms that are necessary for plant growth (Todkari et al., 2001). Seed inoculation with effective Rhizobium inoculant is recommended to ensure additional nodulation and N₂ fixation for maximum growth and yield of soybean crop. The organic manures along with bio fertilizers help in reducing the dose of inorganic fertilizer, which in turn reduces the cost of cultivation and help in improving the soil health. Therefore, this study was undertaken to analyze the effect of combined use of organic and inorganic sources of nutrients on growth, yield and nutrient uptake of soybean in the Vertisols of Rajasthan.

A field experiment was conducted during kharif, 2019 on ARS farm at College of Agriculture, Ummedganj, Kota. The soil of the experimental site was medium black (Vertisols) having clay loam texture, low in available nitrogen (240.50 kg ha^-1), medium in available phosphorus (17.40 kg ha^-1) and high in available potassium (420.55 kg ha^-1) with pH of 7.6, EC (0.36) and medium in organic carbon (0.52%). The experiment consisted of 10 treatments  viz. T₀- Control (Absolute), T₁- RDF (20-40-40), T₂- 75% RDF + FYM (2.0 t ha^-1), T₃- 50% RDF + FYM (4.0 t ha^-1), T₄- 75% RDF+FYM (2.0 t ha^-1)+Rhizobium, T₅- 50% RDF+FYM (4.0 t ha^-1)+ Rhizobium, T₆- 75% RDF+Vermicompost (1.0 t ha^-1), T₇-  50% RDF+Vermicompost (2.0 t ha^-1), T₈- 75% RDF+ Vermicompost (1.0 t ha^-1)+Rhizobium, T₉- 50% RDF+ Vermicompost (2.0 t ha^-1)+Rhizobium. The experiment was laid out in randomised block design and was replicated thrice. Kota is characterized by sub-tropical, semi-arid climate, temperature often exceed 40^oC during summer and sometimes touches 45^oC, minimum temperature falls below 5^oC during winter season. The average rainfall 575 mm, contributed from south-west monsoon during July to September. Soybean crop sown using variety JS-335 with 80 kg ha^-1 seed rate in kharif, 2019.
       
The number of nodules and dry weight of root nodules were recorded at 50 DAS. The five randomly selected plants are uprooted carefully to avoid unwanted shattering of root nodule from each treatment. The nodules of plant^-1 counted and then oven dried at constant temperature to record the nodules dry weight with help of electronic weight balance.While observations on plant growth, yield and yield attributing parameters, such as plant height, plant population, numbers of branches per plant, chlorophyll content, pods per plant, seeds per pod, seed index, oil and protein content, grain yield, haulm yield, harvest index was recorded following standard procedures. Total chlorophyll content of leaves determined by the method advocated by Arnon (1949). Protein content in grain was determined by multiplying per cent nitrogen in grain with a constant factor 6.25 (AOAC 1960). Extraction of oil content by soxhlet extraction unit as per method described by AOAC (1960). Nitrogen was estimated in plant by microkjeldahl distillation method (Bremner, 1965), Phosphorus determination by Vanado Molybdo-phosphoric acid yellow colour method of Jackson (1967) and Potassium determination by flame-photometer as described by Jackson, (1973). To find out the most profitable treatment, economics of various treatments was worked out in terms of net returns and benefit: Cost ratio. In order to test the significance of variation in experimental data obtained for various treatment effects, the data were statistically analysed as described by Fisher (1950).
 
Chlorophyll content (mg g^-1)

Growth attributing characters
 
The data on plant height, plant population and branches produced by plant at different growth stages is presented in Table 1 and depicted in Fig 1. Application of T₈- 75% RDF+ Vermicompost (1.0 t ha^-1)+Rhizobium significantly influent the growth attributing parameters i.e., plant height (58.70 cm), branches plant^-1 (5.60), chlorophyll content (2.84 mg g^-1). The basal application of chemical fertilizers meets the nutritional requirement of crop for proper establishment and growth during the initial period. At subsequent stages vermicompost ensures the proper supply of macro-and micro-nutrients, vitamins and plant growth promoting hormones which have positive effect on plant growth and development. The use of vermicompost would have facilitated better aeration, adequate drainage, improved soil biological activities and created a favourable soil environment for deeper proliferation of roots and higher nutrient extraction from soil, caused more vigorous plant growth. The increased plant height and branches might be due to the involvement of nutrients in cell wall development and cell differentiation which resulted in elongation of shoot and root in plants. Similar results were obtained by Verma et al., (2017) who had reported that an appropriate supply of nutrients through organic and inorganic sources increased the growth attributes of soybean. The results are in conformity with the findings of Morya et al., (2018), Chauhan et al., (2016), Prajapati et al., (2016), Armin et al., (2016), Jain (2015), Konthoujam et al., (2013) and Dwivedi and Kumar (2012).
 

 

 
Number and dry weight of root nodules  
 
A perusal of data (Table 1 and Fig 2) clearly indicated that nutrient management practices considerably influenced the number of nodules. Application of 75% RDF+Vermicompost (1.0 t ha^-1)+Rhizobium (T₈) significantly promoted nodules plant^-1 at 50 DAS (47.40) as compared to absolute control. The similar trend as in total root nodules per plant, the nutrient management practices considerably influenced the production of effective nodules. Application of 75% RDF+ Vermicompost (1.0 t ha^-1)+Rhizobium (T₈) significantly promoted effective nodules at 50 DAS (31.59) as compared to absolute control. Application of 75% RDF + Vermicompost (1.0 t ha^-1)+Rhizobium (T₈) significantly promoted dry weight of nodules at 50 DAS (84.20) as compared to absolute control. The increase in nodules and their dry weight is the response of inoculation by Rhizobium japonicum which might have accelerated the rhizobia activity in the rhizosphere and hence such response. Nodules are the niches of micro organisms and fixed atmospheric nitrogen. This increase ascribed due to better root development and profuse nodulation on account of increase in the rhizobia activity in the rhizosphere due to increased nutrients availability, which resulted in the formation of active and a greater number of root nodules. The results are in close agreement with the findings of Sharma et al., (2018) Konthoujam et al., (2013), Verma et al., (2017) Singh and Kumar (2012), Dwivedi and Kumar (2012) Mohod et al., (2010), Reddy et al., (2009), Dhakal et al., (2016) and Morya et al., (2018).
 

 
Yield and yield attributes
 
The yield and yield attributes are presented in Table 2, Table 3 and Fig 3. Application of T₈- 75% RDF+Vermicompost (1.0 t ha^-1)+Rhizobium significantly influent the yield and yield attributing parameters i.e., pods plant^-1 (41.90), seeds pod^-1 (3.47) grain yield (1380 kg ha^-1), haulm yield (1885 kg ha^-1), biological yield (3325 kg ha^-1) over control (T₀). The maximum harvest index was recorded at the treatment T₈ and the value is (41.52%). Benefits accruing from the integrated use of organic with inorganic fertilizers might be attributed to better supply of nutrients along with conducive physical environment leading to better root activity and higher nutrient absorption, which resulted better plant growth and superior yield attributes responsible for high yield (Thakur et al., 2011). Parjapti et al., (2016) also reported the improved yield attributes of soybean with integration of synthetic fertilizers and organic manures. Photosynthates are synthesized in chloroplasts containing chlorophyll of which the nitrogen is one of the constituents and thus with the increased level of nitrogen the crop productivity also increases. Earlier Sharma et al., (2018) also proved the significance of integrated use of organic and inorganic fertilizers towards improvement in the crop yield of soybean. Comparable findings were reported by Mamia et al., (2018), Kolpe and Bodake (2017), Verma et al., (2017), Dhakal et al., (2016), Chauhan et al., (2016), Jain (2015), Tyagi et al., (2014) and Awasarmal et al., (2013).
 

 

 

 
Quality parameters
 
The nutrient management practices considerably influenced the protein and oil content in seed of soybean. The protein and oil content in soybean affected by various treatments are presented in Table 3. Application of T₈- 75% RDF+ Vermicompost (1.0 t ha^-1)+Rhizobium significantly enhanced protein content (42.25%) and oil content (19.92%). Because nitrogen is a basic constituent of protein and application of nitrogen either inorganic or organic sources ultimately increased the nitrogen availability which results improved protein content in seed. The results are in conformity with the findings of Konthoujam et al., (2013) and Reddy et al., (2009). Increase in oil content might be due to the balanced nutrition of the crop. The macro and micro nutrients supplied through chemical fertilizer and organic manures helped in synthesis of fatty acids and their esterification by accelerating biochemical reactions in glyoxylate cycle. The results are in conformity with the findings of Kolpe et al., (2017) Verma et al., (2017) and Reddy et al., (2009).
 
Nutrient content and uptake
 
The data presented in Table 3 and Fig 4 revealed that the application of 75% RDF+Vermicompost (1.0 tha^-1)+ Rhizobium provided highest nitrogen, phosphorous and potassium content in grain and haulm after harvesting the crop which is significantly superior to control and at par with 75% RDF+FYM (2.0 t ha^-1)+Rhizobium (T₄). The minimum nitrogen content was recorded in absolute control (5.58%). Addition of nutrients to soil through chemical fertilizers and vermicompost significantly enhanced the uptake of different nutrients by grain and haulm in comparison to the control plot. The data presented in Table 4 and Fig 5 revealed that maximum uptake of N, P, K by grain and haulm individually or together was noticed with application of 75% RDF+ Vermicompost (1.0 t ha^-1)+Rhizobium (T₈) than the remaining treatments, found at par with the application of 75% RDF+ FYM (2.0 t ha^-1)+Rhizobium (T₄). The combined application of chemical fertilizers along with enough bulk of vermicompost has always stimulated the uptake of nutrients and partly might be because of stimulated microbes flush and improved root growth due to congenial soil physical condition. The increased nitrogen content and uptake might be due to increased supply of all essential nutrients directly through organic and inorganic sources to crop or indirectly through checking the losses of nutrient from soil solution thereby increase the nutrient use efficiency (Tyagi, 2014). It is expected that with the application of vermicompost there was increase in the availability of phosphorus to plant and because of this, the content of phosphorus in plant also increased. Increment in phosphorus content in plant is also expected due to better buffering capacity of vermicompost for incipient moisture stress and improving phosphorus availability to plant. The results were in conformity with the findings of Dhakal et al., (2016), Tyagi (2014) and Konthoujam et al., (2013).
 

 

 

 
Economics
 
Among nutrient management approaches, the application of T₈- 75% RDF+Vermicompost (1.0 t ha^-1)+Rhizobium had considerably maximum gross return (53042.71 Rs ha^-1), net return (28980.71 Rs ha^-1) and maximum B:C ratio (2.20) compare to other treatment followed by treatment T₄ - 75% RDF+FYM (2.0 t ha^-1)+Rhizobium (Table 3). The higher net return and B: C ratio was associated with its higher grain and haulm yield per unit of added cost. Kolpe and Bodake (2017), Verma et al., (2017) and Konthoujam et al., (2013) also found that the economics of organic and inorganic sources of nutrient treatments resulted in significantly higher gross and net returns over control.

On the basis of present investigation, it can be concluded that the application of 75% RDF+Vermicompost (1.0 t ha^-1)+ Rhizobium (T₈) significantly increased the growth, yield, yield attributing characters and N, P, K content and their uptake, protein and oil content in soybean crop. Application of 75% RDF+Vermicompost (1.0 t ha^-1)+Rhizobium (T₈) had considerably maximum gross return (53042.71 Rs ha^-1), net return (28980.71 Rs ha^-1) and maximum B:C ratio (2.20) compared to other treatments. Hence, this combination of integrated nutrient management proved as productive, remunerative and beneficial for soil health in clay loam soils of ARS, Kota.

None.