​​Potential of Vermiwash Prepared from Different Combinations of Organic Wastes to Improve the Growth, Yield and Quality of Organic Black Gram

Black gram or Urdbean is the fourth most crucial pulse crop in India, being cultivated over about 4.6 million hectares and producing about 24.5 lakh tonnes annually, with average productivity of 533 Kg per hectare in 2020-21 (Anonymous, 2020-21). In Rajasthan, it is cultivated in 5.02 lakh hectares with 1.28 lakh tonnes of production (Anonymous, 2020-21). Being a leguminous crop, it can fix atmospheric nitrogen in its root nodules and can be used as a green manuring crop after picking the pods. Many intensive crop cycles, such as the rice-wheat cropping system, it will fit nicely due to its short duration and photo-insensitive varieties. The black gram plant possesses a deep root system that binds soil particles and thereby reduces soil erosion. The productivity of black gram is low compared to the world’s average because of mainly cultivated under rainfed conditions with inadequate nutrient management on marginal lands that are unfitted for cereals/cash crops.
       
To improve the productivity and quality of black gram, better nutrient management practices that are economically viable and ecologically sound, such as cultivating black gram under organic conditions with potential organic sources of essential plant nutrients. Soil application of essential plant nutrients is often insufficient to meet the crop’s nutrition demand, particularly in short-duration crops like black gram. Therefore, foliar application of organic liquid manures is the value option. Vermiwash is potential liquid manure extracted from earthworms rich vermicomposts. It contains essential plant nutrients and growth hormones like auxin and cytokinine, as well as other secretions, enzymes and a variety of beneficial microbes like heterotrophic bacteria and fungus (Gopal et al., 2010).  Furthermore, the composition of the raw materials used to prepare vermicompost affects the quality of vermiwash produced by earthworms (Rai and Bansiwal, 2008). Foliar spray of vermiwash significantly increased the crops’ growth, yield and quality (Nath and Singh, 2016; Senthilmuruga et al., 2018; Kumar et al., 2021).
       
Several vermiwash studies have been carried out in horticulture crops and only a few studies are available on food crops. The study’s objectives were to analyze the nutrient status, beneficial microbial population and enzymatic activity of the liquid manure and evaluate the effect of liquid manure application on the crop’s growth, yield and quality. The study will lend scientific credence to this low-cost approach because the materials for making liquid manure are readily available locally.

Experiment layout and treatments details         
 
The experiment was carried out at Organic Farm, Rajasthan College of Agriculture, Udaipur, with a latitude/longitude of 24°35'N/73°42'E at an altitude of 582.17 m above mean sea level. The mean weekly meteorological data collected at the Agro Meteorological Observatory in Udaipur during the cropping season shows in Fig 1. The soil of the experimental plot was clay loam having pH 8.1, organic carbon 0.55%, available N, P₂O₅ and K₂O 241.2, 20.9 and 351.3 kg ha^-1, respectively. The experiment was laid down in a randomized block design with three replication comprising nine treatments, i.e. (T₁= vermiwash from 100% cow dung, T₂ = vermiwash from 100% buffalo dung, T₃= vermiwash from 50% cow dung + 25% dry farm waste + 25% green farm waste, T₄= vermiwash from 50% buffalo dung + 25% dry farm waste + 25% green farm waste, T₅= vermiwash from 90% green waste incubated with 10% cow dung, T₆= vermiwash from 90% green waste incubated with 10% buffalo dung, T₇= vermiwash from 90% dry waste incubated with 10% cow dung and T₈= vermiwash from 90% dry waste incubated with 10% buffalo dung and T₉= control (water spray). The black gram crop (var. PU- 31) was sown in the plot (4.0 m × 3.0 m) by adopting a seed rate of 16 kg ha^-1 with a spacing of 30 cm × 10 cm and fertilization as a basal dose of 4 tonnes ha^-1 of vermicompost applied to all the treatments before 15 days of sowing and the rest of was applied through vermiwash liquid manure except control.
 

 
Vermiwash unit
 
Vermicasts were prepared from different organic wastes, i.e., cow dung, buffalo dung, green and dry farm waste, using the earthen pot method. Take an earthen pot of 10-liter capacity and a layer of bricks 2-3 cm was laid in the pot bottom. The pot is filled with organic wastes according to the treatments. Then, 1000 numbers (around 1 kg of earthworm’s culture) of Eisenia foetida in the vermicompost pot. One more pot filled with water was hung above it so that water came out from the pot into the vermicompost pot drop by drop to keep the surface wet. The third pot was placed below it. The Assembly of these three earthen pots was established in a shady place (Fig 2). After 30-35 days, the liquid vermiwash was collected in the third pot and taken to the lab for chemical analysis. The biochemical analysis of vermiwash was done as per the standard procedure shown in Table 1. Foliar spray of 35 days old vermiwash was applied into two splits- first, at the initiation of flowering and second, at the 15 days interval.
 

 

 
Microbial analysis of vermiwash
 
The total bacterial count (TBC), total fungal count (TFC) and total actinomycetes count (TAC) were calculated in triplicate using the standard spread-plate dilution method. T.B.C., T.F.C. and T.A.C. were calculated using nutrient agar, potato dextrose and actinomycetes isolation agar media, respectively (Sharma et al., 2021).
 
Measurement of plant growth parameters, yield and quality analysis
 
Growth parameters viz. root length, nodulation, total chlorophyll, yield and yield attributes and quality content were recorded as per standard procedures/methods (Table 2). Five plants in each plot were selected randomly and labeled for recording observations in all three replications. The most extended root length from the plant’s base to the root’s tip was measured 45 and 60 days after sowing and in centimeters. At the 50% flowering stage, five plants were uprooted randomly without disturbing their roots and nodules. Then dry and clean the plant’s root, a number of the node were separated from the root with the help of forceps and their numbers were recorded. Yield components, namely number of pods plant^-1, number of seeds pod^-1, test weight and seed yield, were recorded at harvest.
 

 
Statistical analysis
 
The data were subjected to statistical analysis of variance as outlined by Panse and Sukhatme (1985).

Vermiwash biochemical analysis
 
Data indicate (Table 3) that the neutral to slightly alkaline pH (7.72), E.C.  (1.39 dSm^-1) and maximum content of nitrogen (0.464%), phosphorus (0.530%) and potassium (0.189%) nutrients were reported in vermiwash treatment T₁ over other treatments. Moreover, high pH and E.C. were recorded in vermiwash treatment T₆ and the lowest N, P and K nutrient content were found in vermiwash treatment T₈. Similar fundings were also reported by Zambare et al., (2008); Hatti et al., (2010); Gopal et al., (2010).
 

       
Significant differences in the microbial population and enzyme activity were observed in different vermiwash treatments (Table 4).
 

 
Total bacterial counts
 
Total bacterial counts (T.B.C.) of various vermiwash treatments ranged from 0.54 to 3.07×10⁸   colony forming units (cfu) per milliliter of organic liquid. The highest counts were found in vermiwash treatment T₁ (3.07×10⁸), while the lowest were found in treatment T₈ (0.54×10⁸).
 
Total fungal counts
 
Vermiwash treatments had total fungal counts (T.F.C.) ranging from 0.12 to 0.79×10⁵ cfu per millilitre of organic liquid. The highest counts were found in vermiwash treatment T₁ (0.79×10⁵), while the lowest concentrations were found in T₇ (0.12×10⁸).
Total actinomycetes counts
 
The mean total actinomycetes counts (T.A.C.) of various vermiwash treatments ranged from 0.05- 2.96×10⁵ cfu per milliliter of organic liquid. The highest counts were observed in vermiwash treatment T₁ (2.96×10⁵) and the lowest counts were observed in T₈ (0.05×10⁵).
 
Enzyme activity
 
The acid phosphatase activity of vermiwash treatments ranged from 2.93 to 7.55 μg ml^-1, alkaline phosphatase activity ranged from 0.74 to 2.54 μg ml^-1 and dehydrogenase activity from 1.27 to 2.77 μgml^-1 and these differences were statistically significant. The highest activity of these enzymes in treatment T₁ and the lowest was observed in treatment T₈. In different vermiwash treatments, the kind of input material used, resulting in diverse microbial populations and enzymatic activity that were significantly altered. Similar result was also reported by Sharma et al., 2021. According to Sreenivasa et al., (2009), organic liquid manures developed using cow products contain many beneficial bacteria, as well as certain useful actinomycetes and fungus. The vermiwash contains an enzyme cocktail and nitrogen fixing bacteria and some phosphate solubilizing bacteria (Zambare et al., 2008).
 
Growth parameters
 
All the vermiwash treatments significantly influenced growth parameters (root length, nodulation and total chlorophyll content of black gram over the control. Significantly maximum root length of 17.00 and 22.00 cm was recorded at 45 and 60 days after sowing, with vermiwash treatment (T₁), which was found to be at par with treatments T₃, T₄ and T₂, respectively and recorded an increase of 21.42 and 25.71 per cent root length at 45 and 60 days after sowing respectively, over control (Table 5). Enhanced root growth can be attributed to readily available essential plant nutrients and growth-promoting hormones in vermiwash, responsible for plants’ rapid growth and development. Similar results were also obtained by Maya et al., (2015).
 

       
Similarly, like the growth of root length, no. of nodes per plant (65.50) at 50% flowering stage showed the maximum in number for vermiwash treatment (T₁) with an increase of 18.38 percent over control and at par with treatment T₃ while the other vermiwash treatments showed a consistent number of nodes. The vermiwash treatment (T₁) showed the maximum chlorophyll content since nutrients available in vermiwash contributed to healthier plants (Table 5) and recorded an increase of 14.87 percent total chlorophyll of black gram over control. Since chlorophyll pigments synthesis in the plants is directly related to the availability of the physio-chemically active N, P, K, S and Fe nutrients. Hence, the availability of these nutrients to plants helps form chlorophyll in the leaves. Vermiwash application has been proved to promote the root formation, nodulation and chlorophyll content, as observed in many field crops (Varghese and Prabha (2014) and Senthilmuruga et al., 2018).
 
Yield and yield attributes
 
Foliar application of treatment (T₁) recorded a significantly higher number of pods plant^-1 (24.67), seeds pod^-1(6), test weight (35.88) and seed yield (800 kg ha^-1), which was found to be at par with the treatments T₃, T₂ and T₄, respectively (Fig 3 and 4). The higher yield and yield attributes under treatment (T₁) may be attributed because of the positive impact of increased availability of plant nutrients, enzymes and beneficial microbes in a balanced form, which resulted in higher growth rate, chlorophyll synthesis, photosynthetic efficiency and assimilate partitioning from source to sink that increased yield attributes and help to produce healthy seed. The result was in agreement with the findings of Bhardwaj and Sharma (2016).
 

 

 
Nutrients and protein content
 
Application of vermiwash treatment (T₁) recorded the highest nitrogen (3.58%) and (2.55%), phosphorus (0.45%) and (0.223%) and potassium (1.30%) and (2.16%), content in seed and haulm respectively, with a significant increase of 15.48 and 62.42 per cent nitrogen, 40 and 15.47 percent phosphorus and 9.2 and 3.8 percent potassium in seed and haulm, respectively, over the control (Table 6). This might be because of the use of potential vermiwash, which helped in producing higher biomass and also in better recovery of N, P and K in the plant (Table 3 and 4). Similar effects have also been observed by Trivedi and Bhatt (2006). The maximum protein content (22.38%) was recorded with vermiwash treatment T₁ and a significant increase of 15.48 per cent over the control (Table 6). It can be due to enhanced absorption of nitrogen, which ultimately increases the protein content in seeds. Similarly, Hoffland et al., (2000) found that spraying vermiwash considerably changes tissue nitrogen content.
 

Our study indicated that vermiwash is a potential source of plant nutrients, beneficial micro-organisms and enzymes. Vermiwash treatment (T₁) is the best liquid manure showing optimum pH, E.C. and highest nutrient content, microbial count and an increased number of enzymes. Foliar application of vermiwash significantly improved black gram’s productivity and quality over the control (water spray). Among the vermiwash treatments, treatment (T₁) showed the highest growth, yield, nutrients and protein content in organic black gram. 

None.