Integrated nutrient management enhances growth, productivity and profitability of greengram (Vigna radiata L.) in rice fallow ecosystems of Eastern India

Introduction

Rice fallow systems offer considerable potential for pulse cultivation in India, particularly in the eastern and southern regions, where about 11.65 million hectares remain fallow after rice harvest (Kumar et al., 2018) [6] . Cultivating greengram (Vigna radiata L.) in these rice fallow areas is a promising approach to increase pulse production, enhance overall system productivity, and maintain soil fertility through biological nitrogen fixation. A major challenge in rice fallow pulse cultivation is the difficulty of applying nutrients through conventional soil methods due to relay cropping and limited residual soil moisture. Under such conditions, foliar nutrient application becomes critical for meeting crop nutritional needs during key growth stages (Ganapathy et al., 2008) [4] . Recent research highlights the importance of foliar feeding for short-duration crops, where soil-applied fertilizers may not be fully available before crop maturity (Kumar et al., 2018) [6] . Growth traits such as plant height, branching, leaf area development, and dry matter accumulation directly influence green gram yield and are strongly affected by nutrient availability during the vegetative stage. Integrating basal fertilization with targeted foliar nutrition can optimize these growth parameters. Despite its potential, rice fallow green gram productivity remains low (300-500 kg ha⁻¹), mainly due to nutrient management constraints. The relay cropping nature of these systems limits conventional soil fertilizer application, making foliar nutrition the primary strategy for supplementing nutrients during critical stages (Ganapathy et al., 2008) [4] . Although recent studies report positive effects of foliar nutrient application in pulses, comprehensive research on the growth, productivity, and profitability of rice fallow green gram under different foliar nutrient management strategies is still limited. This study tests the hypothesis that combining basal fertilization with foliar nutrient sprays enhances green gram growth, yield, and economic returns compared to using basal fertilization or foliar sprays alone.

Materials and Methods

Experimental Site and Design

The field experiment was carried out during the Rabi season of 2017-18 at the Instructional Farm of Orissa University of Agriculture and Technology (OUAT), Bhubaneswar, India, located at 20°15' N latitude, 85°52' E longitude, and 25.9 m above mean sea level. The site falls within the East and Southeastern Coastal Plain Agroclimatic Zone of Odisha, about 64 km from the Bay of Bengal. The experiment was arranged in a randomized block design with three replications and twelve treatments. Each gross plot measured 5.65 m × 5.3 m, while the net plot area was 5.0 m × 5.0 m, with a plant spacing of 30 cm × 10 cm.

Soil Characteristics

The soil at the experimental site was sandy loam with a slightly acidic pH of 5.23. It was low in available nitrogen (182.1 kg ha⁻¹), medium in available phosphorus (16.2 kg ha⁻¹), and high in available potassium (298.4 kg ha⁻¹). The soil had an organic carbon content of 0.55%, a bulk density of 1.45 g cm⁻³, and a water-holding capacity of 37.5%. The greengram variety IPM 02-14 was sown on 17 December 2017 at a seed rate of 20 kg ha⁻¹. Basal nutrients were applied according to the treatments using urea, di-ammonium phosphate (DAP), and muriate of potash (MOP). Foliar sprays were applied with a hand sprayer fitted with a conical nozzle at the preflowering stage (26 DAS) and again 10 days later (36 DAS).

Treatments and Crop Management

Experimental observations 3.1 Pre harvest studies 3.1.1 Plant height

Plant height was recorded to assess the effect of different treatments on growth. Five tagged plants per plot were measured at 15 DAS and subsequently at 15-day intervals until maturity. Height was measured in centimeters from the soil surface to the apex of the main stem.

Branches per plant (no.)

The number of branches per plant was recorded on five tagged plants in each plot at 15 DAS and then at 15-day intervals until maturity.

Leaves per plant (no.)

Leaves were counted on five tagged plants per plot at 15 DAS and at 15-day intervals thereafter until maturity. The counts were averaged to express the number of leaves per plant.

Leaf area

For destructive sampling, all leaves were removed from the collected plants, and leaf area was measured using a leaf area meter. Fresh leaves were used for the measurements, and the readings were averaged to calculate the leaf area per plant.

Leaf area index

The leaf area index (LAI) was calculated by dividing the leaf area per plant by the area of land occupied by that plant, as shown below.

Total leaf area was found out by multiplying actual leaf area per plant with number of plants m -2 .

Dry matter per plant was measured from five randomly selected plants in the designated destructive sampling row of each plot at 15 DAS and at 15-day intervals until maturity using an electronic balance. The samples were first air-dried for two days and then oven-dried at 80°C until a constant weight was achieved.

Shoot dry weight was determined from five randomly selected plants per plot at 15 DAS and at 15-day intervals until maturity using an electronic balance. The samples were air-dried for two days and then oven-dried at 80°C until a constant weight was reached.

Post harvest studies 3.2.1 Pods per plant (no.)

The number of pods per plant was counted on five randomly selected plants from each plot just prior to harvest.

Seeds per pod (no.)

Pods from five randomly selected plants in each plot were harvested, carefully threshed by hand, and the average number of seeds per pod was determined.

From a representative grain sample of each plot, 100 grains were counted and weighed to determine the test weight in grams. Broken seeds were excluded, but shriveled grains were included in the count.

The yield from each net plot was threshed separately to obtain clean seeds. Plot-wise seed yield was recorded after sun-drying the seeds to a standard moisture level, and then the yield was converted to kilograms per hectare (kg ha⁻¹).

Haulm yield (kgha -1 )

Haulm yield was calculated by subtracting the seed yield per plot from the total bundle weight (biological yield) and then converting the result to kilograms per hectare (kg ha⁻¹).

It was calculated by using the following formula Where, economic yield is the seed yield (kg ha -1 ) and biological yield is the total above ground biomass (seed + haulm) yield in kg ha -1 .

Economics

The economics of the different treatments were calculated based on the prevailing market prices of inputs and produce during the study period.

Cost of cultivation is a key component in economic analysis. It can be determined by accounting for the prevailing market prices of inputs, labor wages, and the actual expenses incurred for various operations during the study.

Gross monetary returns represent the total income from the crop produce (seed plus haulm) expressed in ₹ ha⁻¹. These returns were calculated based on the prevailing market prices of the produce at the time of harvest.

Net monetary returns (₹ ha⁻¹) were calculated by deducting the total expenditure (₹ ha⁻¹) from the gross returns, essentially subtracting the cost of cultivation from the gross return. This represents the actual income earned by the farmer. The net monetary returns for the different treatments were calculated using the following formula: Net monetary returns (Rs. ha -1 ) = Gross returns (Rs.ha -1 ) -Cost of cultivation (Rs. ha -1 )

Statistical analysis

All biometric data collected from pre-and post-harvest studies were organized into appropriate tables and subjected to statistical analysis following the Randomized Block Design (RBD) procedure to generate the analysis of variance (ANOVA) table. Treatment differences were tested for significance using the 'F' test. The standard error of the mean (SEm ±) and the critical difference (CD) at the 5% significance level were calculated according to the formulas given by Gomez and Gomez (1984) [5] for result interpretation.

The application of RDF as basal combined with 2% NPK (19:19:19) foliar sprays at 26 and 36 DAS (T 10 ) resulted in the maximum plant height of 37.13 cm, which was significantly higher than all other treatments. The corresponding data are presented in Table 1.

Number of seeds per pod

The highest test weight (33.3 g) was recorded in the treatment with RDF as basal and 2% NPK (19:19:19) foliar sprays at 26 and 36 DAS (T 10 ), closely followed by T 8 and T 9 , and was significantly higher than the other treatments. The lowest test weight (24.6 g) was observed in the control (T 12 ).

The seed yield data (kg ha⁻¹) presented in Table 2 showed that the highest seed yield of 676.4 kg ha⁻¹ was achieved with RDF as basal combined with 2% NPK (20:20:20) foliar sprays at 26 and 36 DAS (T 10 ), which was significantly superior to all other nutrient management practices except T 9 (662 kg ha⁻¹). This best nutrient management practice resulted in a yield increase of approximately 44% over RDF alone (T 1 ) and 133% over the unfertilized control (289.8 kg ha⁻¹).

The highest haulm yield (1,634 kg ha⁻¹) was obtained with RDF as basal combined with 2% NPK (19:19:19) foliar sprays at 26 and 36 DAS (T 10 ), which was significantly higher than most other treatments, except T 9 , T 8 , T 7 , and T 6 . The lowest haulm yield (983 kg ha⁻¹) was recorded in the control (T 12 ).

Harvest index

The data on harvest index (HI) in Table 2 The additional two foliar sprays of 2% DAP nearly doubled the profit compared to RDF alone. The maximum benefit-cost (B:C) ratio of 1.92 was also observed with this treatment, closely followed by RDF as basal plus two sprays of 2% urea at 26 and 36 DAS (T 8 ).

Discussion

Plant height

Nutrient application significantly influenced the plant height of greengram compared to the control. The increase in height was attributed to internode elongation and vigorous root development. The tallest plants (37.13 cm) were recorded in T 10 , closely followed by T 9 . These findings are consistent with Kumar et al. (2018) [6] , who reported increased plant height in black gram with RDF (20:40:40) and 2% NPK (19:19:19) foliar spray at flowering, and are also in agreement with the results of Thakur et al. (2017) [12] .

Branches per plant

The number of branches per plant was significantly higher in T 10 compared to other treatments, except T 9 . The increase in branching was attributed to the combined effect of RDF as basal and two foliar applications of 2% NPK (19:19:19), which enhanced various metabolic processes such as photosynthesis, energy transfer, and symbiotic nitrogen fixation. The greater number of branches and increased plant height may be due to the higher availability of nitrogen, phosphorus, and potassium, which play a crucial role in cell division.

Number of trifoliate leaves per plant, leaf area and LAI

In the present study, the number of leaves per plant increased steadily up to 45 DAS and then declined sharply. The highest leaf area per plant (957.2 cm²) and leaf area index (LAI) of 3.19 were recorded at 45 DAS when RDF was applied as basal along with two 2% foliar sprays of NPK (19:19:19) at 26 and 36 DAS. Similar findings were reported by Thakur et al. (2017) [12] and Bansal and Ahmad (2015) [1] in greengram with RDF and two foliar sprays, as well as by Sritharan et al. (2005) [10] and Senthilkumar et al. (2008) [8] in black gram.

Dry matter accumulation per plant

The growth parameters indicated that plants receiving RDF as basal along with 2% NPK (19:19:19) foliar sprays at 26 and 36 DAS exhibited maximum growth. At harvest, this treatment recorded the highest dry matter accumulation per plant (10.9 g), which was significantly superior to all other treatments. The enhanced growth and development could be attributed to the adequate supply of nitrogen, phosphorus, and potassium through basal and foliar applications during flower initiation and pod formation. This likely maintained higher auxin levels for increased plant height, larger leaf area, and higher chlorophyll content, improving light interception, absorption, and utilization, thereby boosting photosynthetic rates and dry matter accumulation. These results are in agreement with the findings of Thakur et al. (2017) [12] and Takankhar et al. (2017) [11] . Foliar application at later growth stages may have also facilitated effective nutrient translocation within the plant (Kumar et al., 2015) [7] .

Yield attributes

The number of pods per plant is a key yield-determining trait, directly influencing per-plant and per-area production. [13] and Thakur et al. (2017) [12] . Similarly, the highest benefit-cost (B:C) ratio of 1.92 was achieved with RDF as basal and two 2% DAP foliar sprays, followed by RDF as basal with two 2% urea sprays (1.90), while the control had the lowest B:C ratio (1.07). The slightly lower net return and B:C ratio with RDF plus NPK foliar sprays were due to the higher cost of NPK fertilizer. These results align with previous studies reporting improved grain yield, net income, and B:C ratio with basal RDF combined with two 2% DAP foliar applications at 26 and 36 DAS, as observed by Kumar et al.

Yield

(2018) [6] , Shashikumar et al. (2013) [9] , Vinothkumar et al.

(2013) [14] , Dixit and Elamathi (2007) [3] , and Chandrasekhar and Bangarumusamy (2003) [2] .

Summary and Conclusion

A field experiment was conducted during the Rabi season of

References

1. Bansal M, Ahmad A. Effect of nutrient management on growth, yield and quality of summer mungbean (Vigna radiata L.). Bioscan. 2015;10(1):641-5.
2. Chandrasekhar CN, Bangarusamy U. Maximizing the yield of mung bean by foliar application of growth regulating chemicals and nutrients. Madras Agric J. 2003;90(1-3):1425.
3. Dixit PM, Elamathi S. Effect of foliar application of DAP, micronutrients and NAA on growth and yield of green gram (Vigna radiata L.). Legume Res. 2007;30(4):305-7.
4. Ganapathy M, Baradhan G, Ramesh N. Effect of foliar nutrition on reproductive efficiency and grain yield of rice fallow pulses. Legume Res. 2008;31(2):142-4.
5. Gomez KA, Gomez AA. Statistical procedures for agricultural research. New York: Wiley Inter Science Publication; 1984. p. 76-83.
6. Kumar D, Singh RP, Somasundaram J, Simaiya V, Jamra S. Effect of foliar application of nutrients on growth and development of blackgram (Vigna mungo (L.) Hepper) under rainfed Vertisols of Central India. Int J Chem Stud. 2018;6(1):609-13.
7. Kumar S, Patel SK, Ghosh G. Performance of fertilizers and foliar nutrition levels on yield of greengram (Vigna radiata L.). Res Environ Life Sci. 2015;8(2):387-8.
8. Senthil Kumar G, Muthukrishnan P, Ramasamy S, Chandaragiri KK. Effect of organic and inorganic foliar spray on growth and yield of blackgram (Vigna mungo L.). Madras Agric J. 2008;95(1-6):57-60.
9. Shashikumar, Basavarajappa R, Salakinkop SR, Hebbar M, Basavarajappa MP, Patil HY. Influence of foliar nutrition on performance of blackgram (Vigna mungo L.), nutrient uptake and economics under dryland ecosystems. Legume Res. 2013;36(5):422-8.
10. Sritharan, Aravazhi A, Vanangamudi M. Effect of foliar sprays of nutrients and plant growth regulators (PGRs) for yield maximization in blackgram. Madras Agric J. 2005;92(4-6):301-7.
11. Takankhar VG, Karanjikar PN, Bhoye SR. Effect of foliar nutrition on growth, yield and quality of chickpea (Cicer arietinum L.). Asian J Soil Sci. 2017;12(2):296-9.
12. Thakur V, Patil RP, Patil JR, Suma TC, Umesh MR. Influence of foliar nutrition on growth and yield of blackgram under rainfed condition. J Pharmacogn Phytochem. 2017;6(6):33-7.
13. Uma Maheswari M, Karthik A, Ajay Kumar R. Effect of foliar nutrition on growth, yield attributes and seed yield of pulse crops. Int J Curr Microbiol Appl Sci. 2017;6(11):4134-9.
14. Vinoth Kumar C, Vaiyapuri K, Amanullah MM, Gopalaswamy G. Influence of foliar spray of nutrients on yields and economics of soybean. J Biol Sci. 2013;13(6):56.