Physiological and biochemical characters
Liquid bio fertilizer and organic bio stimulants influenced the crop growth rate, total chlorophyll content and soluble protein content during vegetative and flowering stages. Maximum crop growth rate was registered at 1% liquid rhizobium (4.75 and 6.33 g.m-2
) at 60 DAS. Which was followed by 3% panchagavya and 3% seaweed extract. Liquid bio fertilizer are excellent source of macro and micro nutrients, trace elements, amino acid, Plant growth promoting hormones, vitamins, antibiotics, carbohydrates, proteins and other organic matters exhibits plant growth stimulating property under diluted condition (Moshe et al., 2015)
which increased the crop growth. Total chlorophyll content was significantly improved with 1% liquid rhizobium application with value of 3.02 mg g-1
(vegetative stage) and 3.60 mg g-1
(flowering stage). Furthermore, it was followed by foliar application of 3% panchagavya (Fig 1). The increased chlorophyll content in PGPR sprayed plants may be due to the fact that nitrogen is a constituent of chlorophyll molecule (Teotia et al., 2000).
Fig 1: Effect of liquid rhizobium and organic bio stimulants on total chlorophyll content and soluble protein content (mg g-1) in irrigated blackgram (pooled data).
Soluble protein content of the leaf, being a measure of RuBP carboxylase activity, was considered as an index for photosynthetic efficiency. Rubisco enzyme forms nearly 80 per cent of the soluble protein in leaves of many plants (Joseph et al
1981). In the present study, higher soluble protein content (12.51 mg g-1
at vegetative stage and 12.74 mg g-1
at flowering stage) was observed under application 100% RDF + 1% liquid rhizobium followed by foliar spray of 3% panchagavya. 100% RDF + sea weed extract 3% noticed higher soluble protein content with value 12.34 mg g-1
and 12.52 mg g-1
(vegetative stage and flowering stage) over than rest of the treatments (Fig 1). The positive effect of liquid bio fertilizers on soluble protein content might be due to its involvement in the expression and activation of genes responsible for synthesis of rubisco and rubiscoactivate (Xia et al., 2009),
thereby increasing the capacity of CO2
assimilation in the Calvin cycle. The rubisco content per unit leaf area was positively correlated with that of soluble protein content of the leaf (Balachandar et al., 2003).
Antioxidant enzymes activities are significantly influenced by application of liquid rhizobium and organic bio stimulants. The data on antioxidant enzymes are presented Table 1. Nitrate reductase (NR) is an important enzyme for nitrogen assimilation and is a key point of metabolic regulation in crop plants. Thus, NRase is intimately associated with the plant growth and development (Sinha and Nicholas, 1981
). Peroxidases, one of the key antioxidant enzymes, are widely distributed in nature and catalyze oxidation of various electron donor substrates concomitant with the decomposition of H2
. Catalase was a main enzyme to eliminate H2
in the mitochondrion and microbody (Shigeoka et al., 2002).
The reduction trend of H2
content revealed that, gradual increase of catalase enzyme activity during vegetative and flowering stage of the investigation. In the present study, high NRase activity, POD and catalase enzymes activity were observed with application of 1% liquid rhizobium and it was followed by 3% panchagavya. The absolute control recorded the minimum catalase activity and control recorded the maximum value (16.87 and 17.91 μg of H2
). Catalases also played an important role in the fine regulation of reactive oxygen speciesin the cell through activation and deactivation of several apoplastic enzymes might also generate reactive oxygen species under normal conditions (Sairam et al., 1996)
Effect on nodulation
Table 1: Effect of liquid rhizobium and organic bio stimulants on antioxidant enzymes of irrigated blackgram (Pooled data).
Number of completely developed nodules in all the treatments was calculated manually. 100% RDF along with foliar application of 1% liquid rhizobium noticed significantly increased number of nodules plant-1
(22.67 and 23.05) during kharif
. This was followed by 100% RDF + 3% panchagavya (Fig 2). Being, a leguminous crop, blackgram fulfills major part of nitrogen requirement by symbiotic nitrogen fixation with the help of bacterium called Rhizobia. Rhizobium
involve in symbiotic biological nitrogen fixation; survival in soil, Rhizosphere
colonization, infection and nodule development and energy transformation during Nitrogen fixation in root nodules (O’ Hara et al
1988). Symbiotic nitrogen fixation is well known process exclusively driven by bacterial nitrogenase enzyme which specifically reduces atmospheric nitrogen to ammonia in the symbiotic root nodules (Leigh, 2002)
Yield attributes and yield
Fig 2: Effect of liquid rhizobium and organic bio stimulants on crop growth rate (g m-2 day-1) and no. of nodules/plant in irrigated blackgram (pooled data).
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 (Table 2). 100% RDF along with foliar application of 1% liquid rhizobium noticed significantly increased number of pods plant-1
(37.5 and 37.7), number of seeds pod-1
(9.0 and 9.2), grain yield (1004 and 1063 kg ha-1
, respectively) and haulm yield (1936 and 2108 kg ha-1
) and which was followed by 100% RDF + 3% panchagavya. 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.
Table 2: Effect of liquid rhizobium and organic bio stimulants on yield attributes and yield of irrigated blackgram.
In addition to that, the effect of 3% Seaweed extract was on par with 3% dhasagavya. The least grain and haulm 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 B12 produced in the rhizosphere soils (Vardhini and Rao, 1998)
Correlation and regression analysis
The correlation results revealed that all the variables included in the model were positively significant at a one percent level of significance (Table 3). The correlation coefficients of the grain yield with crop growth rate (0.93), total chlorophyll content (0.94), soluble protein content (0.79), nitrate reductase activity (0.52), number of pods plant-1
(0.89) and number of seeds pod-1
(0.29) showed 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 black gram. 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 4). The multiple linear regression equation could be written as,
Grain yield = -174.97 + 7.46 crop growth rate (gm-2
) + 1.91 otal chlorophyll content (mg g-1
) + 0.63 soluble protein content (mg g-1
) + 3.11 nitrate reductase activity (ug NO2
) + 1.51 number of pods plant-1
+ 1.02 number of seeds pod-1.
(0.77) depicts a good model fit, implying that the independent variables caused 77 per cent of the grain yield. All the variables except nitrate reductase activity and number of seeds pod-1
were found statistically significant (Table 4). The slope coefficient of the crop growth rate has shown that when there is one per cent increase incrop growth rate, there would be a significant increase in the grain yield by 7.46 per cent, other variables being held constant. Likewise, when there is a one per cent increase in the variables viz.
, total chlorophyll index, soluble protein content and number of pods plant-1
, there would an increase in the yield by 1.91, 0.63 and 1.51 per cent, respectively. There is strong econometric evidence that the crop growth rate, total chlorophyl content and number of pods plant-1
significantly impact the grain yield of blackgram.
Table 3: Correlation between physio-biochemical parameters and yield attributes (Pooled data).
Table 4: Multiple linear regression estimates the blackgram yield.