​​Residual Effect of Wheat Varieties and Integrated Nutrient Management on Productivity and Profitability of Green Gram under North Gujarat Agro-climatic Condition

Green gram (Vigna radiata L.) is one of the important pulse crops in India. Total annual production of greengram in India is 98.51 million tonnes with the productivity of 3.20 tonnes per hectare during 2017-18 (Anonymous 2017-18). The important green gram growing states in the country are Orissa, Maharashtra andhra Pradesh, Madhya Pradesh, Gujarat, Rajasthan and Bihar. Green gram contains about 25% protein, which is almost two times that of cereals. It is consumed in the form of split pulse as well as whole pulse, which is an essential supplement in cereal based diet. The Green gram Khichdi is recommended to the ill or aged person as it is easily digestible and considered as complete diet. Roti with green gram dal and green gram dal chawal is an important ingredient in the average Indian diet. The biological value improves greatly, when wheat or rice is combined with green gram because of the complementary relationship of the essential amino acids. It is particularly rich in leucine, phenylalanine, lysine, valine, isoleucine etc. In addition to being an important source of human food and animal feed, green gram also plays an important role in sustaining soil fertility by improving soil physical properties and fixing atmospheric nitrogen. It is a drought resistant crop and suitable for dryland farming. Green gram in contrast with green manures, provide grain to augment income and protein as well as reduce the use of mineral nitrogen in wheat-based cropping systems. In areas, where clear cut fallow of a short duration is available succeeding the wheat crop, crop like green gram can be raised as succeeding crop to wheat.
       
Hence, for long term agricultural sustainability, optimization of the crop nutrition through integrated use of all available nutrient sources is a must. Integrated nutrient management involves the conjunctive use of chemical fertilizers, organic manures, bio-fertilizers etc. and assumes greater importance due to decreasing soil health and fertility as well as reduced factor productivity (Prasad, 1999). According to prevailing circumstances, integrated nutrient management practice is perceived as a feasible option to restore soil health and fertility and get sustained higher crop yields. Organic manures, when applied in conjunction with mineral nutrients, not only improve the yield levels but also improves the soil health through their favourable effects on the physical, chemical and biological properties of the soil and thus, help sustain the productivity (Lourduraj, 1999). Use of organic manure supplies primary, secondary and micro-nutrients and helps in avoiding the deficiencies of these nutrients, which in recent year have become the key factor in reducing the response of crops to NPK applied through fertilizers only. Organic manures also have a pronounced residual effect on the soil fertility (Kumari and Singaram, 1996). Biofertilizers are the source of microbial inoculants, which have brought hopes for many countries both economically and environmentally. In developing countries like India, biofertilizers can solve problems of high cost of fertilizers and thus can save the economy of the country (Gupta et al., 2003). Bio-fertilisation is receiving steadily increased attention and recognition because biofertilizers are not only inexpensive but eco-friendly (Mahdi, 1993).
               
Therefore, the present investigation was carried out to study the effect of integrated nutrient management on wheat crop yield and nutrient status of soil after experimentation. It is hypothesised that integrated nutrient management would improve yield and soil nutrient status.

Experimental site and weather
 
The experiment was conducted at Agronomy Instructional Farm, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar (24°-19' N latitude and 72°-19' E longitude with an elevation of 154.52 m above mean sea level) during the summer seasons of years 2016-17 and 2017-18. The mean maximum and minimum temperature was 36.4 and 36.8°C as well as 22.2 and 20.6°C during the growing seasons of both the years, respectively.
       
The soil at the experimental site was loamy sand of Typic Ustipsamments (sand 84%, silt 7.55%, clay 7.09%), neutral reaction (pH 7.4) with EC of 0.14 dS/m, low in organic carbon (0.24%) and available N (159 kg/ha), medium in available P₂O₅ (38.9 kg/ha) and available K₂O (287 kg/ha) and low in Zn (0.41 mg/kg).The details of physico-chemical properties of experimental soil are given in Table 1.
 


Experimental design and field management
 
The experiment was conducted to find out the residual effect of wheat varieties and integrated nutrient management on greengram crop yield. Treatments were laid out in factorial randomized block design with three replications. First factor included four wheat cultivars viz., GW 273 (V₁), GW 322 (V₂), GW 451(V₃) and GW 496(V₄) and second factor comprised of six integrated nutrient management practices viz., control (N₁), 100% RDF (N₂), 100% RDF + Azotobacter+ PSB (N₃), 75% RDF + Azotobacter + PSB (N₄), 75% RDF + Azotobacter + PSB + ZnSO₄ (N₅) and 50% RDF + 25% N through FYM + Azotobacter+ PSB + ZnSO₄ (N₆).
       
Crop was grown as per the recommended practices except the treatments under study. Field was prepared for sowing of crop and furrows were opened at 30 cm spacing with tractor. Four varieties of wheat i.e. GW 273, GW 322, GW 451 and GW 496 have been sown. No fertilizer application was made as per the treatments. Wheat cultivars on 17^th and 14^th November and harvested on 3^rd and 1^st March during 2016-17 and 2017-18, respectively. After one week sowing of green gram was done with the seed rate of 18 kg/ha on 18^th and 8^th March and harvested on 23^rd and 14^th May during 2016-17 and 2017-18, respectively. Total four irrigations were given in greengram during entire season. Weeds were controlled by spraying pendimethalin (1.0 kg a.i./ha) as pre-emergence followed by one interculturing and one hand weeding when required during crop season in both the years.
 
Sampling and measurement
 
Growth attributes
 
Plant height and number of branches per plant were recorded from five plants selected randomly and tagged permanently from each net plot. Height of individual plant was measured in cm at harvest from base of the plant to the top of the plant by using metre scale and the number of branches per plant was counted of the tagged plants. The data were averaged for both the observations.
 
Yield attributes and yield
 
Number of pods per plant was counted from theselected five plants in each net plot at harvest.After discarding border rows from each experimental plot, the crop was harvested and bundled. After proper sun drying for few days these were weighed to record biological yield. The produce was threshed and after proper cleaning it was weighed to record the seed yield (kg/ha). Stover yield was calculated by subtracting seed yield from biological yield. The biological, seed and stover yields (including sample weight) recorded in kg/net plot was standardized to 8-10 per cent moisture and then weight was converted to per hectare by multiplying appropriate factor.
 
Protein content in seed
 
The seed samples were drawn from each net plot and subjected to chemical analysis. Nitrogen content of seed was determined by micro Kjeldahl digestion and distillation method (Jackson, 1978). Thereafter, the protein content (%) of seed was calculated by multiplying nitrogen content of the seed (%) with the factor 6.25 and was expressed as percentage on dry weight basis for each treatment.
 
Nutrient content
 
The seed and stover samples were collected at threshing from each plot were air dried and then ground to a fine powder for estimation of nitrogen, phosphorus and potassium concentration by standard methods given below.
 
Constituent           Method

Nitrogen (%)           Kjeldahl’s method (Jackson, 1973)
Phosphorus (%)     Vanadomolybdo phosphoric yellow color method (Jackson, 1973)
Potassium (%)        Flame photometer method (Jackson, 1978)
 
Nutrient uptake
 
The total uptake of nitrogen, phosphorus and potassium in seed and stover were calculated by using following expression.
 
 Available N, P, K, OC and Zn in soil
 
For estimation of available N, P, K, OC and Zn in soil, the samples were collected from 0-15 cm depth, dried, ground and passed through 0.2 mm sieve. Available N was estimated following (Subbaiah and Asija, 1956), available P as per (Olsen et al.,1954), available K as per (Hanway and Heidal, 1952), available Organic Carbon as per (Walkley and Black, 1934) and available Zn as per (Hanway and Heidal, 1952).

Effect of wheat varieties
 
The results showed that the growth parameters, yield attributes, yield, nutrient content and uptake of greengram crop did not influence significantly due to residual effect of different wheat varieties.
 
Effect of integrated nutrient management
 
Growth parameters
 
The greengram crop was grown without fertilizer application and under the influence of different integrated nutrient management treatments, significant variation was observed on growth parameters. At harvest, significantly higher plant height (51.67 cm), maximum number of branches per plant (6.90) were observed under application of 50% RDF + 25% N through FYM + Azotobacter + PSB + ZnSO₄, the lower plant height and less number of branches per plant was recorded with the control (no fertilizer) treatment presented in Table 2.
 

       
The plant growth is the function of photosynthetic activity of the plants, translocation of photosynthates within the plant, which ultimately depend on their capacity to utilize available nutrients. This might be due to an adequate amount of nutrients supply that enhanced the cell division and cell enlargement and helped to convert more solar energy into chemical energy. Application of inorganic fertilizers with bio-fertilizers might have supplied the adequate and continuous amount of nutrients at different growth stages due to release of sufficient amount of nutrients by mineralization at a constant level that resulted in higher plant growth, which reflect as higher plant height of the crop. The increase in no. of branches per plant was attributed due to higher N uptake by the crop (Table 3). The beneficial effect of optimum and balanced fertilization involving organic with inorganic and bio fertilizers on number of branches per plant have also been investigated by (Jain et al., 1995; Upadhyay et al., 1999; Jat et al., 2012; Patel et al., 2013) with respect to plant height.
 

 
Yield attributes and yields
 
The residual effect due to integrated nutrient management treatment i.e. 50% RDF + 25% N through FYM + Azotobacter + PSB + ZnSO₄ recorded significantly the higher number of pods per plant (22.98), Test weight (38.72g), seed yield (669 kg/ha) and stover yield (1406 kg/ha). Significantly, the lower number of pods per plant, Test weight, seed yield and stover yields were recorded with nutrient management treatment control (no fertilizer) presented in Table 2.
       
This was largely attributed to better growth of plant which resulted in adequate supply of photosynthates for development of sink under higher level of integrated nutrient management. Positive response in terms of yield attributes to integrated nutrient management have also been reported by (Rajkhova et al., 2002; Yakadri et al., 2002; Chaudhary et al., 2003; Reddy et al., 2011; Patel et al., 2013).
       
The highest seed yield per hectare gained under these treatments might be due to chemical fertilizer in conjunction with organic and bio fertilizers that might have provided favourable soil environment and nourishment for better plant growth resulted in maximum seed yield per hectare. The higher yield in these treatments was due to cumulative effect of elevated growth stature as well as yield structure. Moreover, bio-fertilizers might have helped in increasing uptake of nutrients and conservation and availability of moisture to the plant. The increase in greengram seed yield with addition of inorganic and bio-fertilizers may be attributed to the fact that biofertilizer being the store house of nutrients that also release the applied nutrients at its optimum and improve the soil physical condition. This may be due to better synthesis of chlorophyll in leaves. This finding indicated that the combined application of well decomposed FYM with chemical fertilizers and bio-fertilizers was superior to sole inorganic fertilizer application. The results were supported by the findings of (Acharya and mondal et al., 2010; Ghanshyam et al., 2010; Jat et al., 2012; Patel et al., 2013).
       
Moreover, the application of chemical fertilizers along with bio-fertilizers and organic fertilizers has given residual effect on nutrient availability in the soil to the next crop; greengram utilized residual nitrogen as starter for their vegetative growth due to higher photosynthetic rates and chlorophyll contents of the plant. The increased availability of nutrients under these treatments might have improved the growth attributes that enhanced the photosynthesis and translocation of carbohydrates to sink site which ultimately led to positive increase in stover yield. The higher availability of nutrients might have increased its uptake which increased cell size and enhanced cell division, seems to have played an important role in increasing the plant height and yield. This finding confirms to those reported by (Reddy et al., 2011; Jat et al., 2012; Patel et al., 2012; Patel et al., 2013).
 
Quality parameter
 
The residual effect of all the integrated nutrient management treatments incorporated in preceding wheat crop on the succeeding greengram showed significant improvement in protein content as compared to control (N₁). The higher protein content (22.68%) were recorded under application of 50% RDF + 25% N through FYM+ Azotobacter + PSB + ZnSO₄ (N₆). Minimum protein content of 20.32% was noted with treatment N₁ (control) presented in Table 2.
       
It is an established fact that protein content is dependent on its growth and nutritional composition. Increase in seed protein content may be due to enhanced uptake and translocation of residual nitrates which was remain present in the soil due to the soil fixation and not used completely by previous crop. These nutrients utilized by succeeding greengram crop that provide nitrogen for amino acid synthesis. Increase in protein content might be due to increased N concentration in seed that is integral part of protein synthesis. Increased protein content might be due to adequate supply of nitrogen. Adequate supply of N is associated with the vigorous vegetative growth and dark green colour. Balanced and adequate supply of nitrogen in relation to other nutrients developed favourable conditions for the growth. The supply of nitrogen is related to the protein formation. Further, it is seemed that organic manure improved physical, chemical and biological properties of the soil and this led to improved root growth and development, improved water and nutrient uptake resulting into improved seed quality in terms of higher seed protein content. Similar results found by (Chesti et al., 2012; Jat et al., 2012; Patel et al., 2013).
 
Nutrients content in seed and stover
 
Thenutrients content (%) in seed and stover were significantly influenced by residual effect of different integrated nutrient management treatments. Maximum nitrogen, phosphorus and potassium content in seed  3.629%, 0.473%, 0.635% and in stover 0.751%, 0.231%, 0.985 % were noted under treatment N₆ i.e., 50% RDF + 25% N through FYM+ Azotobacter + PSB + ZnSO₄ being statistically at par with N₃, N₂, N₅ and N₄ sequentially presented in Table 3.
 
Nutrients uptake in seed and stover
 
Thenutrients uptake (kg/ha) by seed and stover were significantly influenced by the residual effect of different treatments of integrated nutrient management. The higher values of nutrients uptake by seed 24.30, 3.17, 4.25 kg/ha and stover 10.55, 3.24, 13.83 kg/ha of N:P:K respectively were noted under treatment N₆(50% RDF + 25% N through FYM+ Azotobacter + PSB + ZnSO₄) but was statistically at par with N₃ (100% RDF + Azotobacter+ PSB) and N₂ (100% RDF/ha). The minimum uptake of NPK by seed 18.46, 2.50, 3.33 kg/ha and stover 8.36, 2.54, 10.70 kg/ha were observed with N₁ (control) presented in Table 3.
       
The higher removal of N and P with treatment N₆might be due to better development of root and shoot of plants, that resulted in higher N and P uptake. These results are in accordance with those reported by (Ghanshyam et al., 2010; Jat et al., 2012; Patel et al., 2013) with respect to N and P contents as well as their uptake.
 
Available N, P₂O₅ and K₂O in soil after harvest
 
The significant effect of integrated nutrient management on available N, P₂O₅ and K₂O was found in soil after harvest of greengram. The treatment N₃ (100% RDF + Azotobacter+ PSB) recorded significantly higher values of available N and P₂O₅ in soil after harvest, but it was statistically at par with the treatment N₂, N₄, N₅ and N₆ in case of available N and P₂O₅ in pooled analysis. The treatment N₁ control (No fertilizer) recorded significantly lower available N and P₂O₅. In case of available K₂O status the treatments showed non-significant effect in soil after harvest of greengram during both years as well as in pooled.
       
(Das et al., 2009) revealed that integrated nutrient management improved the residual soil fertility after greengram to a greater extent and the gain in available organic carbon, nitrogen and P₂O₅ over the initial soil nutrient status. (Kacha et al., 2008) observed that application of castor cake in chilli enhanced the available nitrogen status of the soil over no castor cake treatment. This might be due to higher quantity of organic manure along with bio-fertilizers viz. Rhizobium and PSB, which accumulated in soil resulting in build up of nutrients in the soil. Increase in available N might be due to the direct addition of N through organic manure and greater multiplication of soil microbes, which could convert organically bound N to inorganic form. Similar results have also been reported by (Gorade et al., 2014).
 
Available Organic Carbon in soil after harvest
 
Among the treatments, conjunctive applications of organic and inorganic fertilizers in different combinations get influenced over treatment control in consideration of available organic carbon content in soil in presented Table 4. Significantly higher organic carbon content was recorded in soil under the treatment N₆ (50% RDF + 25% N through FYM + Azotobacter + PSB + ZnSO₄). However, significantly higher (0.267%) and the lowest (0.203%) values of available organic carbon in soil were recorded with the treatments N₆ (50% RDF + 25% N through organic manure + Azotobacter + PSB + ZnSO₄) and N₁ (control) in pooled analysis, respectively.
       
The organic carbon after harvest of the crop was observed under higher inputs (Integrated Nutrient Management), as these inputs resulted in higher vegetative growth of plants which implies that profuse root system has developed and thereby after harvest of crop more amount of root debris remained in the soil which converted in carbon source reflected in terms of higher organic carbon in soil. Increasing levels of NPK fertilization significantly increased the available N, P, K and Organic Carbon content in the soil (Kumari and Singaram, 1996).
 
Available zinc in soil after harvest
 
The application of 50% RDF + 25% N through FYM + Azotobacter + PSB + ZnSO₄ (N₆) and 75% RDF + Azotobacter + PSB + ZnSO₄ (N₅) recorded significantly higher content of available zinc in soil over rest of the treatments presented in Table 4. However, both these treatments were remained at par with each other. Application of treatments N₆ (50% RDF + 25% N through FYM + Azotobacter + PSB + ZnSO₄) registered significantly higher (0.464 mg/kg) and lower (0.380 mg/kg) content of available zinc in soil. Zinc exerts beneficial effect on N assimilation via its influence on nitrate reductase activity. Thus, N content in seed is significantly increased by following application of zinc. (Chaudhary et al., 2014) were also observed the same trend of results in green gram.
 

 
Economics
 
Effect of varieties
 
The higher gross realization (₹ 38,012/ha), net realization (₹ 16,957/ha) and BCR (0.81) were secured by variety GW 273 (V₁) as compared to other varieties.
 
Effect of integrated nutrient management
 
Data on economics as influenced by different integrated nutrient management treatments are presented in Table 5. The higher gross realization (₹ 39,593/ha), net realization (₹ 18,538/ha) was incurred under the treatment N₆ (50% RDF + 25% N through FYM+ Azotobacter + PSB + ZnSO₄) with the BCR value of 0.88. The next better treatment in view of gross and net realization was N₃ (100% RDF+ Azotobacter+ PSB) which recorded the gross and net realization of ₹ 38,902/ha and ₹ 17,847/ha, respectively, with the BCR value of 0.85. The lowest gross realization ₹ 33,596, net realization of ₹ 12,541/ha and BCR value of 0.60 were found in N₁ (control). The results are in conformity with those reported by (Ambhore, 2004; Jat et al., 2012;  Patel et al., 2013) with respect to higher net income and BCR.
 

Residual effect of treatments on growing succeeding green gram without fertilization after wheat i.e., variety GW 273 grown with 50% RDF + 25% N through FYM + Azotobacter + PSB + ZnSO₄ secured higher green gram yield, net return and B:C ratio on loamy sand soil of North Gujarat.Sequence cropping of wheat (variety GW 451 with 100% RDF + Azotobacter + PSB) - green gram (without fertilization) produced higher net return and B:C ratio.