Effect on growth characters
The data on growth characters of blackgram are presented in Table 1. Various plant growth characters of blackgram crop were significantly influenced by liquid rhizobium with organic bio stimulants.
100% RDF along with foliar application of 1% liquid rhizobium registered increased plant height of 40.9 cm, 42.0 cm at harvest stage during
kharif and
rabi and it was followed by foliar spraying of panchagavya @ 3 % and sea weed extract @ 3 %. According to
Gardner et al., (1991), nitrogen nutrients are needed by plants for the synthesis of amino acids and proteins, especially at plant growth points to accelerate the process of plant growth such as cell division and cell elongation to increase plant height. Spraying of panchagavya and sea weed extract stimulated the growth and plant height by increasing the auxin and cytokinin content in blackgram
(Kumar et al., 2011).
Significantly higher number of branches plant
-1 was found with the application of 100% RDF + 1% liquid rhizobium followed by 100 % RDF + panchagavya @ 3%. This helped to increase the cell division activity, cell expansion and elongation, ultimately leading to more number of branches plant
-1. Nitrogen can stimulate vegetative growth of plants as well as the number of branches. The influence of seaweed extract, dhasagavya and fish amino acid on the endogenous levels of hormones enhanced the photosynthesis and nitrate assimilation
(Senthil et al., 2003).
The increase in DMP was significantly more with 100% RDF + foliar application of 1% liquid rhizobium (2995 and 3087 kg/ha) and 3% panchagavya (2713 and 2801 kg/ha) during
kharif and
rabi. It might have contained microbial metabolites in appreciable amount that help in maintaining the opening of stomata for longer period both in optimum and adverse conditions during the crop growth which led to increased DMP. The increased availability of nitrogen due to the presence of nitrogen fixing bacteria
(Jeyakumar et al., 2008). Also, the biosynthesis of plant growth promoting substances like cytokinins, IAA, GA, vitamins and antibiotic substances by the microbial inoculants acted in synergy to it
(Zhang et al., 2008).
LAI is an important indicator of total photosynthetic surface area available to the plant for the production of photosynthates, which accumulate in the developing sink. Higher LAI was recorded under 100% RDF + 1% liquid rhizobium (4.92, 5.87 during
kharif and
rabi), which was followed by 100% RDF + 3% panchagavya (Table 1). Liquid bio fertilizers played an important role in increasing the number of leaves, leaf elongation, chlorophyll content and thus led to increase in leaf area index. The overall improvement in the growth of blackgram with the addition of seaweed extract, dhasagavya and fish amino acid could be ascribed to their pivotal role in several physiological and biochemical processes,
viz., root development, photosynthesis, energy transfer reaction and symbiotic biological N fixation process. The similar results were also reported by
Subramani and Solaimalai (2000).
Yield attributes and yield
A perusal of data revealed that yield attributes and the yield increased significantly with the foliar application of Liquid rhizobium and organic bio stimulants in blackgram over control.
100% RDF along with foliar application of 1% liquid noticed significantly increased number of pods plant
-1 (37.5 and 37.7), number of seeds pod
-1 (9.0 and 9.2), pod weight (15.62 and 16.03 g) and pod length (5.84 and 5.91 cm) during
kharif and
rabi. This was followed by 100 % RDF + 3 % panchagavya (Table 2). This was due to the enhanced root and shoot development, solar radiation interception and nutrients uptake. Further, the translocation and accumulation of photosynthates in the economic sinks resulted in increased yield attributes and biological yield of blackgram.
Grain yield (1004 and 1063 kg ha
-1 during
kharif and
rabi, respectively) and haulm yield (1936 and 2108 kg ha
-1) were significantly higher with application of 100% RDF + 1% liquid rhizobium and 100 % RDF + 3% panchagavya. In addition to that, the effect of 3 % Seaweed extract was on par with 3% dhasagavya (Table 3). The least grain and straw yield was observed in control plot. The overall effect of rhizobium in increasing the grain yield of this crop was primarily due to the enhanced availability of nutrients, through nitrogen fixation by bacteria production of plant growth promoting (PGP) substances and vitamins, especially B
12 produced in the rhizosphere soils. As observed in the present investigation, liquid bio fertilizers and organic bio stimulants play a favorable role in improving various metabolic activities through enhanced nucleic acid metabolism and protein synthesis (
Vardhini and Rao, 1998).
Correlation and regression analysis
The correlation results were represented in Table 4. Its results revealed that all the variables included in the model were positively significant at one percent level of significance and these signs emphasize all the variables would attribute to the grain yield of the blackgram. The correlation coefficients of the grain yield with plant height (0.83), number of branches plant
-1 (0.55), DMP (0.92), leaf area index (0.66), number of pods plant
-1 (0.89), number of seeds pod
-1 (0.89), pod weight (0.98) and pod length (0.81) show that all the attributes were positively related and that strongly proves when there is an increment in these variables, there would be an increase in the yield of the blackgram. So, all these variables are included as the independent variables in the multiple linear regression model
(Xiaolu et al., 2019). The multiple linear regressions were estimated to measure the relationship and the change in magnitude of the grain yield due to the other prescribed parameters (Table 5). The multiple linear regression equation could be written as,
Grain yield = -101.07 + 1.11 plant height + 0.83 no. of branches plant
-1 + 1.28 DMP (kg/ha) + 0.19 LAI + 2.08 number of pods plant
-1 + 2.54 number of seeds pod
-1 + 0.18 pod weight plant
-1 + 0.07 pod lenght plant
-1
The R
2 (0.81) depicts a good sign of model fit which implies that 81 percent of the grain yield was caused by the independent variables. All the variables except plant height except plant height and DMP were found statistically significant (Table 5). The slope coefficient of the number of branches has shown that when there is one percent increase number of branches, there would be a significant increase in the grain yield by 0.83 percent, other variables being held constant. Likewise, when there is a one percent increase in the variables viz., leaf area index, number of pods plant
-1, number of seeds pod
-1, pod weight and pod length, there would an increase in the yield by 0.19, 2.08, 2.54, 0.18 and 0.07 per cent respectively
(Tittonell et al., 2007). There is strong econometric evidence that the number of branches and pod weight have a significant impact on the grain production of black gram.