​​Effect of Integrated Nutrient Management on Quality, Yield, Nutrient Content and Uptake of Black Gram (Vigna mungo L.) in the South-eastern Plain of Rajasthan

Black gram (Vigna mungo L.) is one of the most important pulse crops among the various grain legumes grown in India. As per Vavilov (1951), it is indigenous to India and belong to Leguminosae. It is highly nutritious containing higher amount of 22-24% protein, 1.3% fat and 60% carbohydrates on dry weight basis and it is rich source of calcium and iron. It is the most popular pulse and can be most appropriately referred to as the king of the pulses.
       
INM includes the intelligent use of organic, inorganic and on-line biological resources so as to sustain optimum yield, improve or maintain the soil physical and chemical properties and provide crop nutrition packages which are technically sound, economically attractive practically feasible and environmentally safe (Kachhave et al., 2009; Desai et al., 2020). INM is also important for marginal farmers who cannot meet the expense of supply crop nutrients from end-to-end costly chemical fertilizers. The biofertilizers have shown boosting results in sustaining the crop productivity and improving the soil fertility (Tomar et al., 2015; Ghosh and Joseph, 2008).
               
Organic manures, on the other side are responsible to act as a good substrate for the growth of micro-organisms and sustain a favorable nutrients supply environment and improve soil fertility and productivity (Mannivanan et al., 2009). Uses of imbalanced or exorbitant supplements and long pull utilization of inorganic manures without natural augmentation harms the soil physical, chemical and organic properties directed to declining nutrient use efficiency bringing contrary effects on air (Aulakh and Adhya, 2005) and groundwater quality (Aulakh et al., 2009) causing health hazards. In these region soils, N, P, S and Zn deficiencies are principal yield-limiting factors for crop production. Besides many reasons were found for low production of black gram viz., lack of improved cultural practices, cultivation on marginal and sub marginal lands of poor fertility, imbalanced use of fertilizers, lack of improved nutrient management technique, dependent only on chemical fertilizers are the major bottle necks responsible for poor yield of Kharif pulses including blackgram (Amruta et al., 2016). These problems can be overcome to some extent by adopting the integrated nutrient management approach which helps to sustain the soil fertility as well as productivity by balanced fertilization and optimum integration of inorganic and organic source of nutrients (Govindan and Thirumurugan 2005).

The experiment was conducted in Field No.12 at Institutional Farm, Agricultural Research Station, Ummedganj, Kota (Rajasthan), which is situated at South-Eastern part of Rajasthan. The regions fall under Agro-climatic Zone V B (Humid South eastern Plains) of Rajasthan. This zone possesses typical sub-tropical conditions with maximum and minimum temperatures ranged between 23.46°C to 37.24°C and 17.5°C to 34.7°C during Kharif, 2019. The total amount of rainfall received during black gram crop growth in 2019 was 712 mm. The soil of experimental site was clay loam in texture, slightly saline in reaction. The experimental soil was medium in available nitrogen (173 kg ha^-1) and phosphorus (11 kg ha^-1) while high in potassium (478 kg ha^-1) and sufficient in DTPA extractable micronutrients with pH (7.8) and EC (0.60 dSm^-1). Source of nutrients applied were urea for nitrogen, DAP for phosphorus and K₂SO₄ for potassium. The FYM contained 0.5% N, 0.2% P and 0.5% K, which was applied as per treatments two weeks before sowing. The seeds were inoculated with Rhizobium and LMn 16 @ 400 g per 20 kg seed.
       
The experiment was carried out  in three replications following randomized block design with factorial concept having eighteen treatments as follows viz., T₁=75% RDF + Control +Rhizobium, T₂=75% RDF + Control +LMn16, T₃=75% RDF+ Control+Rhizobium+LMn16, T₄=75% RDF+ 5 ton FYM + Rhizobium, T₅=75% RDF+ 5 ton FYM +LMn16, T₆=75% RDF+ 5ton FYM +Rhizobium + LMn16, T₇=100% RDF+ Control +Rhizobium, T₈=100% RDF+ Control +LMn16, T₉=100% RDF+ Control +Rhizobium +LMn16, T₁₀=100% RDF+ 5 ton FYM +Rhizobium, T₁₁=100% RDF+ 5 ton FYM +LMn16, T₁₂=100% RDF+ 5 ton FYM +Rhizobium +LMn16, T₁₃=125% RDF+ Control + Rhizobium, T₁₄=125% RDF+ Control + LMn16, T₁₅=125% RDF+ Control +Rhizobium +LMn16, T₁₆=125% RDF+ 5 ton FYM + Rhizobium, T₁₇=125% RDF+ 5 ton FYM +LMn16, T₁₈=125% RDF+ 5 ton FYM +Rhizobium + LMn16. Data on growth and yield parameters like plant height, number of branches per plant, number of pods per plant, straw yield, biological yield and grain yield were recorded as per standard procedures. Plant samples (grain and straw) were collected after harvesting from each of the plots.
               
For analysis of plant nutrients in seed and straw after collection the plant samples were first washed with running regular water to wipe out totally recognizable soil particles followed by washing with 0.01 N HCl lastly with deionized water. From that point forward, plant samples were dried in a hot air oven at 65°C for 48 h until the steady weight was accomplished. In the wake of drying, the samples were ground to a fine powder for additional investigation. After wet digestion of plant sample with mixture of H₂SO₄ and H₂O₂ (Jackson, 1973) nitrogen was estimated in plant sample by modified Kjeldahl method (Snell and Snell 1949). Digestion of sample for phosphorus and potassium content was by tri acid mixture HNO₃: HClO₄:H₂SO₄ ratio of 10:4:1 as per procedure Vando molybdo phosphoric acid yellow colour method (Jackson 1973), Potassium was determined using flame photometer and cationic micronutrients viz., Fe, Mn, Zn and Cu were extracted by using DTPA extraction procedure (0.005 M diethylene triamine Penta acetic acid (DTPA) + 0.01 M CaCl₂.2H₂O + 0.1 M triethanolamine or TEA) buffered at pH 7.3 as described by Lindsay and Norvell (1978). The data were statistically analyzed by adopting appropriate method of standard analysis of variance (Gomez and Gomez 1984).

Quality parameters
 
Data regarding to protein content and protein yield of black gram was exhibited in Table 1. The maximum protein content and protein yield were recorded under 125% RDF (20.9%, 188 kg ha^-1) followed by 100% RDF (20.5%, 163 kg ha^-1) and lowest under fertility level 75% RDF (20.3%, 141 kg ha^-1). The increasing nutrient content particularly nitrogen and phosphorus was attributed to biological nitrogen fixation and mineralization which ultimately increased the protein yield of the black gram (Kumawat et al., 2015). Application of farm yard manure had no significant influence either on protein content or protein yield in blackgram (Table 1) (Patil et al., 2010). Further it is evident from the data depicted in Table 1, that protein content was not statistically influenced by rhizobium treatments while protein yield was observed highest under application of Rhizobium + LMn16 followed by Rhizobium alone while, minimum protein yield was obtained with under treatment LMn16 culture treated plot (Shekhawat et al., 2017). The protein content of seed is directly related to the nitrogen content, so application of higher fertilization (125% RDF) with FYM and bio fertilizers significantly increased the nitrogen content and assimilation power of plants which is responsible for increasing the protein content as well as protein yield and improved the quality of black-gram variety under study. Similarly, results were reported by Shelvakumar et al., 2012.
 

 
A perusal of data presented in Table 1 indicated that total root nodule per plant and dry weight of nodule were significantly increased with increasing fertility levels 125% RDF (24.0, 44.4 mg) followed by 100% RDF (23.8, 42.8 mg), 75% RDF (21.3, 36.3 mg) respectively. Data revealed that the application of FYM @ 5 t ha^-1 significantly increased the root nodule per plant and their dry weight (24.1, 43.8 mg) as compared to the control plot (22.0, 38.4 mg). The extent of increase in root nodule was noticed 9.3% higher over control. Similarly, the maximum nodule count and dry weight was observed in treatments receiving seed inoculation with Rhizobium + LMn16 (24.2, 46.7 mg) as compared to without combination of seed inoculation LMn16 (21.6, 35.7 mg) and Rhizobium (23.3, 41.1 mg) respectively. Due to application of higher fertility level with FYM and bio fertilizers vigorous plant growth which enhance the plant energy synthesis by the photosynthesis process increases store energy and synthesized the large quantity of food material that was responsible for source–sink relationship. Which, is ultimately had positive effect on plant height, nodule count and their dry weight, resultant that the increased the grain yield straw yield and biological yield of black gram (Kumavat et al., 2015; Kachhave et al., 2009). Thus, it proved that in present investigation bio fertilizer and optimum quantity of fertilizers resulted in plant growth and quality parameters.
 
Yield
 
Data from Table 1 revealed that application of higher fertility level like 125% RDF significantly increased the grain yield (900 kg ha-1), straw yield (3741 kg ha^-1) and biological yield (4640 kg ha^-1). Further data revealed that application of FYM @ 5 t ha^-1 significantly increased the grain yield (830 kg ha^-1), straw yield (3518 kg ha^-1) and biological yield (4345 kg ha^-1) over control treatment. Inoculation of Rhizobium + LMn16 also resulted in significant increases in the grain yield (862 kg ha^-1) and biological yield (4432 kg ha^-1) over sole application of Rhizobium and LMn16. Probably increment in the growth parameters and yield of black gram viz., biological yield, grain yield, straw yield and harvest index improvement might be due to accumulation of carbohydrate in plant and early and sufficient availability of plant growth regulator and chelating agent secretion leading to the better nutritional environment in the root zone of black gram (Kumpawat, 2010; Meena et al., 2021).
 
Nutrient content of blackgram
 
The perusal of data of nitrogen in seed and straw of black gram mentioned in Table 2 indicated that nitrogen, phosphorus and potassium content in seed was found highest in 125% RDF (3.35, 0.45 and 1.07 %) respectively followed by 100% RDF and lowest in 75% RDF. Similar trend was observed in straw of blackgram (Table 2). The application of FYM @ 5t ha^-1 registered highest nitrogen, phosphorus and potassium content in seed and straw compared to control plot. Among the biofertilizer, the highest nitrogen content in seed and straw were found in treatment receiving Rhizobium + LMn16 (3.31%, 1.69%) followed by Rhizobium (3.30%, 1.61%) and LMn16 (3.28%, 1.57%), respectively. Similarly, phosphorus and potassium in seed was noticed highest in application of Rhizobium + LMn16 (0.48%, 0.29%) followed by Rhizobium (0.46%, 0.28%) and in LMn16 (0.38%, 0.23%) respectively (Kumar and Jat, 2010; Yadav et al., 2017). The  results further indicated that maximum level of micronutrients like zinc was recorded in seed and straw with application of 125% RDF followed by 100% RDF, while minimum value of zinc content was observed in 75% RDF (Table 2). The maximum zinc content was recorded in seed treatment receiving of FYM @ 5t ha^-1 (10.1, 15.1 mg, respectively) over the control (9.69, 13.5 mg in seed and straw respectively). In response of different biofertilizers, the maximum zinc content was observed treatment with the application of Rhizobium + LMn16 (9.37, 14.4 mg, respectively) followed by treatment under Rhizobium culture (9.87, 14.3 mg), LMn16 (9.82, 14.8 mg) respectively. Similarly, iron, copper and manganese content also increase in response to different treatment combinations (Table 2) (Husain et al., 2011; Yadav et al., 2017). It observed that the favorable effect on soil as well as on plant was due to positive soil micro climate regime in soil and its effect on both plant and soil in terms of increase in the macro and micro nutrient concentration (Gosh and Das 2011; Swaminathan et al., 2020).
 

 
Nutrient uptake
 
Nutrient uptake of macro and micro nutrients by seed and straw in blackgram significantly increased with different fertility doses. The highest nitrogen, phosphorus and potassium uptake was found in seed of black gram with application of 125 % RDF (30, 4.5 and 9.6 kg ha^-1) respectively compared to lower doses tested. Similarly, treatments receiving FYM resulted in found highest uptake by seed nitrogen, phosphorus and potassium (27.35, 3.83 and 8.24 kg ha^-1) respectively as compare to control plot. Highest nitrogen, phosphorus and potassium uptake in seed were noticed in treatment receiving Rhizobium + LMn16 (28.41, 4.24 and 8.64 kg ha^-1 respectively) as compared to sole application of Rhizobium and LMn16. Similar, trend was noticed in case of straw uptake in relation to different treatment combinations (Table 3). Application of higher fertilizer doses, FYM @ 5 t ha^-1and biofertilizer (Rhizobium + LMn16) resulted in uptake of micronutrients (Zn, Cu, Mn and Fe) by seed and straw of black gram. Similar results were reported by (Dekhane et al., 2011; Gosh and Das, 2011). Organic manure and bio fertilizers with inorganic fertilizers increased the absorption power of the soil for cations and anions particularly nitrogen, potassium and some micronutrients. These ions are released gradually during entire growth period of the crops which might have increased concentration and uptake of nutrients (Desai et al., 2020). Farm yard manure and biofertilizers along with optimum dose of fertilizer helps in improving quality of soil and efficient supply of nutrient. Which ultimately increase the sustainability of crops with the zero adverse impact on agro eco system by enhancing the availability of applied as well as native soil nutrient (Amruta et al., 2016). It helps in providing balanced nutrition to crop and minimizes the antagonistic effects resulting from hidden deficiencies (Kumar and Jat, 2010; Kudi and Shingh, 2016).
 

The study concluded that the variation in the availability of plant macro and micronutrients, plant growth and yield of black gram in response to inorganic to organic fertilization varied quantitatively based on the nature. In INM application of organic nutrient sources particularly FYM and biofertilizers integrating with optimal doses of chemical fertilizers substantially enhances the growth, yield, nutrient content and uptake of black gram and improve sustainability under south eastern plains of Rajasthan. This experiment outcomes high light significance of soil application of higher fertilizer doses, farm yard manure and biofertilizers for increasing the productivity with improved quality of blackgram.

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