Growth parameters, yield and phosphorous fertilization
The P management had significant effect on growth parameters and yield (Table 1). The data revealed that maximum plant height (76.7cm) and DMP (47.4 g/plant) was observed in treatment T
7 application of P @ 60 kg/ha of + DGRC culture followed by treatment T
6. This may be due to improved availability of Phosphorus. The accessibility of phosphorus also improves the utilization of N and K in the plant system. Phosphorus plays a crucial role in the energy cycle of plants, contributing significantly to enhancing plant growth. Ensuring optimal phosphorus availability is essential for sustaining crop growth, as phosphorus is integral to various aspects such as root growth and development, respiration, nucleic acid synthesis, nitrogen fixation, plant maturity and seed production
(Naik et al., 2022). The maximum pod yield (3710 Kg/ha) and haulm yield (5601 Kg/ha) was recorded with combined application of 60 kg P/ha and seed treatment with DGRC culture (Table 1). This might be due to optimum availability of nutrients with the integrated use of chemical and organic sources might speed up the growth and development processes leading to higher yield. Moreover the integrated use of organics with inorganic fertilizers leads to better utilization of soil moisture, uptake of soil nutrient and improves soil organic matters which increase the soil water holding capacity, soil aggregation, microbial activity and soil porosity ultimately leading to higher crop productivity
(Yadav et al., 2019).
Yield attributes and phosphorous fertilization
The effects of different phosphorus fertilization treatments on groundnut were found to be significantly impactful (Table 2). The maximum number of pods/plant (28.6), 100 kernel weight (53.7 g), shelling % (74
.2%) and SMK (83.9%) were registered with integrated application of 60 kg P/ha + seed treatment with DGRC culture and it was followed by application of 40 kg/ha of P + DGRC culture. The integrated utilization of organic and inorganic phosphorus sources led to improvements across various aspects of soil quality. This included enhancements in the physical attributes such as soil structure and water-holding capacity, chemical properties like buffering capacity, cation exchange capacity and the availability of macro and micronutrients, while also reducing phosphate fixation
(Naik et al., 2022). Furthermore, there were improvements in the biological properties of the soil, such as increased organic matter content, soil microbial biomass and diversity of soil microorganisms. These combined improvements created an optimal environment conducive to the higher growth and development of plants, ultimately resulting in improved yield attributes.
Nutrient uptake and root nodules
The application of phosphorus fertilization had a significant impact on various key aspects such as nutrient uptake and root nodules, as detailed in Table 3 and Table 4. Significantly higher numbers of nodules/plant (39.9 and 65.4 at 40 DAS and 80 DAS, respectively) and increased dry weight of nodules/plant (20.7 mg and 39.6 mg at 40 DAS and 80 DAS, respectively) were observed with the application of a higher dose of phosphorus (60 kg/ha) in conjunction with DGRC culture. This combination led to a 38% increase in nodule numbers per plant compared to plots without phosphorus application (Control). These results indicate that while genetic factors play a role in nodulation and plant growth, external factors such as phosphorus fertilizer, inoculants containing beneficial microorganisms like rhizobium and organic manure can also significantly influence these processes. This highlights the importance of considering both genetic and environmental factors in optimizing plant growth and nodulation in agricultural practices
(Kumar et al., 2017).
Highest nutrient uptake of nitrogen (98.55 kg/ha), phosphorus (16.39 kg/ha) and potassium (57.85 kg/ha) in groundnut after harvest was noticed in the application of 60 kg P
2O
5/ha + DGRC culture. The integrated application of phosphorus (P) exists in various organic and inorganic forms within the soil, including soil organic matter, minerals and the soil solution. Plants absorb P primarily as orthophosphate ions from the soil solution. To maintain equilibrium, P moves from more readily available organic and inorganic pools into the soil solution. This accessible or labile P includes mineralizable organic P and readily exchangeable adsorbed P, transitioning from less accessible pools that include stable organic P and P strongly bound to soil minerals and compounds, into labile pools to maintain P equilibrium status in the soils. This process ultimately increases nutrient uptake and the biological yield of crops
(Hao and Chang, 2002).
Numerical variables analysis
The correlation results revealed that all the variables included in the model were positively significant at a one percent level of significance (Table 5). These findings suggest that each variable contributes to the groundnut’s grain yield. As grain yield is the most critical variable that directly reflects the yield, it was compared with other plant-related parameters to determine their relationship with each other. The correlation coefficients indicate that grain yield is positively correlated with pods per plant (0.77), shelling (0.86), plant height (0.93), dry matter production (0.96) except for 100 seed kernel weight
(Ravi, et al., 2024). These results confirm that an increase in these variables would lead to an increase in groundnut yield. Therefore, all of these variables were included as independent variables in the multiple linear regression model
(Ajaykumar et al., 2022). Multiple linear regressions, which were employed to measure the relationship and the magnitude of the change in grain yield due to the other prescribed parameters. The multiple linear regression equation could be written as,
Grain yield = -2995.73 + 49.11 pods/plant (No’s) + 8.58 100 kernel weight (gm) + 18.82 shelling (%) + 13.89 SMK (%) + 27.32 plant height (cm) + 46.71 dry matter production (gm/plant)
The R
2 value of 0.76 indicates a good fit for the model, suggesting that the independent variables accounted for 76 per cent of the grain yield (Table 6). Except for 100 kernel weight (gm) and SMK (%), all variables were found to be statistically significant. The slope coefficient of pods per plant revealed that a one per cent increase in pods per plant would lead to a significant 47.03 per cent increase in yield, holding all other variables constant. Similarly, a one per cent increase in shelling (%), plant height (cm) and dry matter production (g/plant) would result in yield increases of 17.14, 26.30 and 45.58 per cent, respectively
(Tittonell et al., 2008). However, an increase in weed control efficiency resulted in a negative impact on yield, with a one per cent increase causing a 3.54 per cent decrease in yield.
Economics
The economic indicators including the cost of cultivation, gross return, net returns and the benefit-cost ratio were presented in Table 7. The effect of different phosphorus fertilization on the economics of groundnut cultivation showed that application of 60 kg P /ha + seed treatment with DGRC culture resulted in higher gross returns (141234 Rs. ha
-1), net returns (90762 Rs. ha
-1) and a B:C ratio of 2.80, closely followed by the treatment with application of 40 kg/ha of P + DGRC culture. Integrated phosphorus (P) management, combining chemical P fertilizer with DGRC has resulted in a reduced need for inorganic P fertilizer by plants. This reduction is likely to save farmers money by eliminating the costly use of chemical P fertilizers. The increased crop productivity achieved through this integrated approach is likely the primary driver behind the higher net returns observed under integrated P management tailored with DGRC culture. The results are consistent with the findings reported by
(Naik et al., 2022).
