Enhancing soil fertility, yield, and quality in green gram (Vigna radiata L. Wilczek) through integrated nutrient management

Vijay Kumar^{* *}Correspondence: Vijay Kumar, School of Agriculture, RNB Global University, Bikaner, Rajasthan, India, Email:

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Introduction

Green gram (Vigna radiate L. Wilczek) commonly known as mung bean and golden gram, is one of the important kharif pulse crop. It ranks third among all pulses grown in India after chickpea and pigeon pea. It is quite versatile crop grown for seeds, green manure and forage; as mixed or sole crop either on residual moisture of the previous crop or as a catch crop to make use of the land left fallow between two main season crops. It makes a good manure if incorporated into soil. Further, it enriches the soil by atmospheric nitrogen fixation through root nodules. The crop gives such a heavy vegetative growth and covers the ground so well that it checks the soil erosion in problem areas and can later be ploughed down for green manure. It has considerable potential as an alternative pulse crop in dry land farming. This crop is of great importance because of availability of short duration (65-70 days), high yielding and quick growing varieties [1].

In India, mung bean growing states are Rajasthan, Uttar Pradesh, Maharashtra, Karnataka, Andhra Pradesh and Odisha. Rajasthan ranks first in area, while Maharashtra ranks first in production. Kerala is the leading state in productivity with an average of 824 kg ha^-1 whereas, the national average is 548 kg ha^-1. Although green gram is a legume and capable of fixing atmospheric nitrogen, still it responds to small quantity of nitrogenous fertilizers applied as starter dose. In terms of significance, phosphorus is most indispensable mineral nutrient for pulse crops as it helps in better root growth and development and thereby making them more efficient in biological nitrogen fixation. Phosphorus is an essential constituent of nucleic acids such as Ribonucleic Acid (RNA) and Deoxyribonucleic Acid (DNA), Adenosine Diphosphate (ADP) and Adenosine Triphosphate (ATP), nucleoproteins, amino acids, proteins, phosphatides, phytin, several co-enzymes viz. thiamine, pyrophosphate and pyrodoxyl phosphate [2,3].

Materials and Methods

In order to determine the physico-chemical properties of soil, soil samples (0 cm-15 cm depth) were collected from different spots of the experimental field prior to sowing and fertilization. A representative composite soil sample was prepared by mixing all these samples together. The soil sample after drying was passed through 2.0 mm sieve and then subsequently used for mechanical, physical and chemical analysis. The experimental site soil was clay loam in texture, slightly alkaline in reaction. The soil was medium in available nitrogen, phosphorus while high in potassium and sufficient in DTPA extractable micronutrients.

To assess the fertility status of soil, the soil sample (0 cm-15 cm depth), from each plot at harvest of crop was taken. The samples were passed through 2 mm plastic sieve to avoid metallic contamination. The soil sample were analysed for EC, pH and Organic Carbon (OC) and available Nitrogen, Phosphorus, Potassium (NPK) and cationic micronutrients (Copper (Cu), Zinc (Zn), Iron (Fe) and Manganese (Mn)) content as per methods [4].

The experiment was laid out in factorial randomized block design with three replications. The treatment combinations were randomized with the help of randomization technique.

Treatment application

Fertility levels: Nitrogen and phosphorus were applied through urea and Diammonium Phosphate (DAP), respectively as per treatments as basal doses at the time of sowing. Whole amount of vermicompost as per treatment was broadcasted uniformly at the time of sowing and incorporated in the soil.

Biofertilizer levels: The required seeds were treated with bavistin at 2 g/kg of seed to control seed borne diseases. Later on seeds were inoculated with Rhizobium and PSB culture or both as per treatments, using standard method and dried in shade.

Seed rate and sowing

The seeds were sown by ‘kera’ method with row spacing of 30 cm by hand plough at a depth of 5 cm using a seed rate of 20 kg ha^-1. The variety of green gram (SML-668) was used as the test crop and the sowing was done on 18 July 2015.

Thinning, hoeing and weeding

To maintain uniform plant, stand at an intra-row spacing of 10 cm, extra plant was thinned out 10 days after sowing (DAS). In order to minimize weed competition, weeding and hoeing was done manually 19 and 28 days after sowing to facilitate aeration and removal of weeds.

Harvesting

The crop was harvested from net plot area separately from each plot. The harvested material of each plot was tied up in bundles and tagged.

Statistical analysis

Analysis of variance and test of significance: In order to test the significance of variation in experimental data obtained for various treatment effects. The critical differences were calculated to assess the significance of treatment mean wherever the ‘F’ test was found significant at 5% level of probability. To elucidate the nature and magnitude of treatment effects, summary tables along with Standard Error of the mean (SEm) ± Critical Difference (CD) (p=0.05) were prepared and are given in the text of the chapter “results” and their analyses of variance are given in appendices at the end.

Economics of treatments: The economics of treatments is the most important consideration making any recommendation to the farmers for its wide adoption. For calculation of economics, the average treatment yield along with prevailing market rates for inputs and outputs were used. Hence, to evaluate the effectiveness and profitability of the treatments comprehensive economics including net returns and Benefit cost (B/C) ratio was calculated so that most effective and remunerative treatment could be recommended. The details of calculation are given in appendices at the end [5-7].

Results and Discussion

The data related to various criteria used for treatment evaluation were analysed statistically using standard statistical methods to test their significance. The data regarding the effect of fertility and biofertilizer levels on net return and benefit cost ratio of green gram are being summarized in Table 1.

Table 1: Effect of fertility and biofertilizer levels on net returns and benefit cost ratio.

Net return

Effect of fertility levels:A perusal of data in Table 1, revealed that with the application of fertility levels, the net return under 75% RDF+vermicompost (2 t ha^-1), 100% RDF and 100% RDF+vermicompost (2 t ha^-1) treatments significantly increased as compared to 75% RDF. However, the increase in net return with 100% RDF+vermicompost (2 t ha^-1) was statistically at par with 75% RDF+vermicompost (2 t ha^-1). The application of 75% RDF+vermicompost (2 t ha^-1), 100% RDF and 100% RDF+vermicompost (2 t ha^-1) increased the net return to the tune of 28.98%, 14.51% and 36.63% respectively, over 75% RDF [8-10].

Effect of bioferilizers:A critical examination of data in Table 1, revealed that due to inoculation of green gram seed with Rhizobium, PSB and Rhizobium+PSB, the net returns significantly increased in comparison to control. Further, the increase in net returns with Rhizobium+PSB was statistically significant over Rhizobium as well as PSB inoculations. However, the increase in net returns with inoculation of Rhizobium was statistically at par with that of PSB. The extent of increase in net return of green gram with Rhizobium, PSB and Rhizobium+PSB inoculation was 38.31%, 33.14% and 54.57% respectively over control.

Interactive effective of fertility and biofertilizer levels:The interactive effect of fertility and biofertilizer levels on the net returns was found significant (Table 2). The significantly highest net returns were obtained under treatment combination F₄B₃, which was at par with the treatment combinations of F₂B₃. Minimum net returns were recorded under F₁B₀ treatment.

Table 2: Interactive effect of fertility and biofertilizer levels on net returns (ha^-1).

Benefit cost ratio

Effect of fertility levels: The benefit cost ratio under 75% RDF+vermicompost (2 t ha^-1), 100% RDF and 100% RDF+vermicompost (2 t ha^-1) treatments significantly increased as compared to 75% RDF treatment. The highest B/C ratio (1.80) was recorded with 100% RDF+vermicompost (2 t ha^-1). The application of 75% RDF+vermicompost (2 t ha^-1), 100% RDF and 100% RDF+vermicompost (2 t ha^-1) increased the B/C ratio to the extent of 9.32%, 8.07% and 11.80% respectively, over 75% RDF.

Effect of bioferilizers: Due to inoculation of green gram seed with Rhizobium, PSB and Rhizobium+PSB, the B/C ratio significantly increased in comparison to control. The highest B/C ratio (2.08) was obtained with B3 (Rhizobium+PSB). However, the increase in B/C ratio with inoculation of Rhizobium was statistically at par with that of PSB. The extent of increase in B/C ratio with Rhizobium, PSB and Rhizobium+PSB inoculation was 36.23%, 31.16% and 50.72% respectively, over control [11,12].

The application of 100% RDF+VC at 2 t ha^-1 to green gram crop significantly increased the net return (38837) and B/C ratio (1.80) over others levels of RDF and vermicompost. Likewise, inoculations of greengram seeds with Rhizobium+PSB also significantly increased net returns (40102) and B/C (2.08) ratio over Rhizobium, PSB and control (Table 1). It is clear that in both the treatments there was significant increase in seed and haulm yield which ultimately gave more net returns and B/C ratio over the input cost incurred in these treatments in comparison to others treatments. These results are in close conformity with those of Meena et al., [13].

Interactive effect of fertility and biofertilizer levels: The significantly highest net returns (48109 ha^-1) and B/C ratio (2.22) were obtained with combined use of 100% RDF+VC at 2 t ha^-1 and Rhizobium+PSB (F₂B₃), which were significantly higher as compared to other treatment combinations (Table 2). However, it is at par with F₂B₃ (44987 ha^-1). It is obvious because the seed and haulm yield of green gram also increased significantly under this treatment which is main contributor to net returns and thus resulted in higher net returns under application of 100% RDF+VC at 2 t ha^-1 and Rhizobium+PSB. These results are in close conformity with those of Meena et al., [13].

Conclusion

On the basis of one-year field experimentation, it can be concluded that under agro climatic condition of Kanpur, application of 100% RDF+VC at 2 t ha^-1+Rhizobium+PSB (F₄B₃), is the better option for realizing higher productivity, content and uptake of nutrients, net returns and B/C ratio of green gram and is the better option for improved fertility status of soil. A significant response to the application of aforesaid treatment was observed. However, highest economic green gram seed yield (1386.07 kg ha^-1) and net return (48109 ha^-1) was observed in treatment combination of F₄B₃ (100% RDF+VC at 2 t ha^-1+Rhizobium+PSB) with B/C ratio of 2.22, which was at par with F₂B₃ (75% RDF+VC at 2 t ha^-1+Rhizobium+PSB). The result of the present investigation reveals the significance of fertility levels with the combination of vermicompost and biofertilizer levels in green gram crop for maximization of yield and profits.

However, the highest available nitrogen, phosphorus, potassium, copper, zinc, iron and manganese status of soil after harvesting of green gram crop were observed under fertility level 100% RDF+VC at 2 t ha^-1 (F₄) and inoculation of Rhizobium+PSB (B₃) treatment as compared to 75% RDF (F₁) and control (B₀), respectively.

However, these results are only indicative and require further experimentation for confirmation before making final recommendation to the farmers.

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