Vermicompost—The Miracle Plant Growth Promoter

After reading this article you will learn about vermicompost as the miracle plant growth promoter.

Strategies of reducing net CO₂ to be included here vermicompost is proving to be highly nutritive ‘organic fertilizer’ and more powerful ‘growth promoter’ over the conventional composts and a ‘protective’ farm input (increasing the physical, chemical and biological properties of soil, restoring and improving its natural fertility) against the ‘destructive’ chemical fertilizers which has destroyed the soil properties and decreased its natural fertility over the years.

Vermicompost is rich in NKP (nitrogen 23%, potassium 1.85-2.25% and phosphorus 1.55-2.25%), micronutrients, beneficial soil microbes and also contain ‘plant growth hormones and enzymes’. It is scientifically proving as ‘miracle growth promoter and also plant protector’ from pests and diseases.

Vermicompost retains nutrients for long time and while the conventional compost fails to deliver the required amount of macro- and micro-nutrients including the vital NKP to plants in shorter time, the vermicompost does.

Protective Compost versus the Destructive Chemical Fertilizers:

Chemical fertilizers which ushered the ‘green revolution’ in the 1950-60’s came as a ‘mixed blessing’ for mankind. It boosted food productivity, but at the cost of environment and society. It dramatically increased the ‘quantity’ of the food produced but decreased its ‘nutritional quality’ and also the ‘soil fertility’ over the years. It killed the beneficial soil organisms which help in renewing natural fertility.

It also impaired the power of ‘biological resistance’ in crops making them more susceptible to pests and diseases. Over the years it has worked like a ‘slow poison’ for the soil with a serious ‘withdrawal symptoms’.

The excessive use of ‘nitrogenous fertilizer’ (urea) has also led to increase in the level of ‘inorganic nitrogen’ content in groundwater (through leaching effects) and in the human food with grave consequences for the human health. Chemically grown foods have adversely affected human health.

Organic farming systems with the aid of various nutrients of biological origin such as compost are thought to be the answer for the ‘food safety and farm security’ in future. Among them ‘composts’ made from bio-degradation of organics of MSW (municipal solid waste) which is being generated in huge amount every day all over the world are most important.

The organic fraction of the MSW (about 70-80%) containing plenty of nitrogen (N), potash (K) and phosphorus (P) is a good source of macro- and micro-nutrients for the soil.

Composts also contain plenty of ‘beneficial soil microbes’ which help in ‘soil regeneration’ and ‘fertility improvement’ and protect them from degradation while also promoting growth in plants. Composts also protect plants from pests and diseases.

Properties of farm soil using compost vis-a-vis chemical fertilizers:

Suhane (2007) studied the chemical and biological properties of soil under organic farming (using various types of composts) and chemical farming (using chemical fertilizers—urea (N), phosphates (P) and potash (K). Results are given in Table 19.3.

All compost (including vermicompost), are produced from some ‘waste materials’ of society which is converted into a ‘valuable resource’. It is like ‘killing two birds in one shot’. More significant is that it is of biological origin i.e. a ‘renewable resource’ and will be readily available to mankind in future. Whereas, chemical fertilizers are made from petroleum products which are ‘non-renewable’ and a ‘depleting’ resource.

While in the use of compost the environment is ‘benefitted’ at all stages from production (salvaging waste and diverting them from landfills and reducing greenhouse gases) to application in farms (adding beneficial microbes to soil and improving biochemical properties), in the use of chemical fertilizers the environment is ‘harmed’ at all stages—from procurement of raw materials from petroleum industries to production in factories (generating huge amount of chemical wastes and pollutants) and application in farms (adversely affecting beneficial soil micro-organisms and soil chemistry).

Composts: The Miracle Plant Growth Promoter and Protector:

Composts are aerobically decomposed products of organic wastes such as the cattle dung and animal droppings, farm and forest wastes and the municipal solid wastes (MSW). It is called a ‘miracle’ for plant growth. It can supply balanced nutrients to plant roots and stimulate growth; increase organic matter content of the soil including the ‘humic substances’ that affect nutrient accumulation and promote root growth.

Vermicompost in fact improve the total physical and chemical properties of the soil. They also add useful micro-organisms to the soil and provide food for the existing soil micro-organisms and thus increase their biological properties and capacity of self-renewal of soil fertility.

One ton of compost may contain 5 kg of nitrogen (N), 2.5 kg of phosphorus (P₂O₅) and 3 kg of potash (K₂O). Compost made from poultry droppings contains highest nutrient level among all compost.

There are other agronomic benefits of composts application, such as high levels of soil-borne disease suppression and removal of soil salinity. It has been reported that mean root disease was reduced from 82% to 18% in tomato and from 98% to 26% in capsicum in soils amended with compost.

It is found that with application of compost in vineyards, levels of exchangeable sodium (Na) under vine were at least reduced to 50%.

Treated vines produced 23% more grapes due to 18% increase in bunch numbers. Biological properties of soil were also improved with up to ten-fold increase in total microbial counts. Most significant was three-fold increase in the population of earthworms under the vine with long-term benefits to the soil.

All composts work as a ‘slow-release fertilizer’ whereas chemical fertilizers release their nutrients rather quickly in soil and soon get depleted. Nitrogen and phosphorus particularly are not all available to plant roots in the first year because N and P in organic matter are resistant to decay.

Nitrogen is about one half effective as compared to chemical fertilizer, but phosphorus and potassium are as effective as chemical fertilizers.

With continued application of compost the organic nitrogen tends to be released at constant rate from the accumulated ‘humus’ and the net overall efficiency of nitrogen over a period of years is considerably greater than 50% of that of chemical fertilizers. Availability of phosphorus is sometimes much greater.

Moreover, significant amount of nitrogen is lost from soil due to oxidation in sunlight. It has been calculated that upon application of 100 kg urea (N) in farm soil, 40-50 kg gets oxidised and escapes as ‘ammonia’ (NH₃) into the air, about 20-25 Kg leaches underground polluting the groundwater, while only 20-25 kg is available to plants (Suhane, 2007).

Vermicompost vis-a-vis Conventional Compost and Chemical Fertilizers:

Conventional compositing and vermicomposting are quite distinct processes particularly with respect to optimum temperatures for each process and the type of decomposer microbial communities that pre-dominate during active processing.

While ‘thermophilic bacteria’ pre­dominate in conventional composting, ‘mesophilic bacteria and fungi’ pre-dominate in vermicomposting. Although the conventional composting process is completed in about 8 weeks, but additional 4 weeks is required for ‘curing’.

Curing involves the further aerobic decomposition of some compounds, organic acids and large particles that remain after compositing. Less oxygen and water is required during curing. Compost that has had insufficient curing may damage crops. Vermicomposting takes nearly half the time of conventional composting and vermicompost do not require any curing and can be used straightway after production.

Vermicomposts have much ‘finer structure’ than ordinary compost and contain nutrients in forms that are readily available for plant uptake. Vermicomposts have outstanding chemical and biological properties with ‘plant growth regulators’ (lacking in other composts) and significantly larger and ‘diverse microbial populations’ than the conventional thermophilic composts.

The conventional compost was higher in ‘ammonium’, while the vermicompost tended to be higher in ‘nitrates’, which is the more available form of nitrogen.

Vermicompost has higher N availability than the conventional compost on a weight basis and the supply of several other plant nutrients e.g. phosphorus (P), potassium (K), sulfur (S) and magnesium (Mg), were significantly increased by adding vermicompost as compared to conventional compost to soil.

Vermicompost retains nutrient for long time and while the conventional compost fails to deliver the required amount of macro- and micro-nutrients including the vital NKP (nitrogen, potassium and phosphorus) to plants in shorter time, the vermicompost does.

The agronomic impacts of vermicompost and inorganic (chemical) fertilizers on strawberries when applied separately and also in combination. Vermicompost was applied at the rate of 10 tons/ha while the inorganic fertilizers (nitrogen, phosphorus, potassium) at the rate of 85 (N), 155 (P), 125 (K) kg/ha.

While there was not much difference in the ‘dry shoot weight’ or strawberries, the ‘yield’ of marketable strawberries and the ‘weight’ of the ‘largest fruit’ was greater on plants in plots grown on vermicompost as compared to inorganic fertilizers in 220 days after transplanting. Also there were more ‘runners’ and ‘flowers’ on plants grown on vermicompost.

Strawberries grown on inorganic fertilizers amended with vermicompost had significantly greater dry shoot weight, leaf areas and more number of flowers than grown exclusively on inorganics in 110 days after transplanting. Also, farm soils applied with vermicompost had significantly greater ‘microbial biomass’ than the one applied with inorganic fertilizers.

Vermicompost: A Soil Conditioner:

Significantly, vermicompost works as a ‘soil conditioner’ and its continued application over the years lead to total improvement in the quality of soil and farmland, even the degraded and sodic soils. It has been found that application of vermicompost at the rate 6 tons/ha resulted in reduction of 73.68 in sodicity (ESP) and increase of 829.33 kg/ha of available nitrogen (N) leading to significant improvement in soil quality.

Vermicompost: The Miracle Plant Growth Promoter and Protector:

Vermicompost is a nutritive ‘organic fertilizer’ rich in NKP (nitrogen 23% potassium 1.85-2.25% and phosphorus 1.55-2.25%), micronutrients, beneficial soil microbes like ‘nitrogen-fixing bacteria’ and ‘mycorrhizal fungi’ and are scientifically proving as ‘miracle growth promoters and protectors’.

Vermicast contains as high as 7.37% nitrogen (N) and 19.58% phosphorus as P2O5. Suhane (2004) showed that exchangeable potassium (K) was over 95% higher in vermicompost. There are also good amount of calcium (Ca), magnesium (Mg), zinc (Zn) and manganese (Mn).

Additionally, vermicompost contain enzyme like amylase, lipase, cellulase and chitinase, which continue to break down organic matter in the soil (to release the nutrients and make it available to the plant roots) even after they have been excreted.

Annual application of adequate amount of vermicompost also lead to significant increase in soil enzyme activities such as ‘urease’, ‘phosphomonoesterase’, ‘phosphodiesterase’ and ‘arylsulphatase’. The soil treated with vermicompost has significantly more electrical conductivity (EC) and near neutral pH.

Vermicompost as very ‘high porosity’, aeration’, ‘drainage’ and ‘water holding capacity’. They have a vast surface area, providing strong absorbability and retention of nutrients. They appear to retain more nutrients for longer period of time.

Study showed that soil amended with vermicompost had significantly greater ‘soil bulk density’ and hence porous and lighter and never compacted. Increase in porosity has been attributed to increased number of pores in the 30-50 pm and 50-500 size ranges and decrease in number of pores greater than 500 pm.

It has been found to influence on all yield parameters such as improved seed germination, enhanced rate of seedling growth, flowering and fruiting of major crops like wheat, paddy, corn sugarcane, tomato, potato, brinjal, okra, spinach, grape and strawberry as well as of flowering plants like petunias, marigolds, sunflowers, chrysanthemums and poinsettias.

In all growth trails the best growth responses were exhibited when the vermicompost constituted a relatively small proportion (10-20%) of the total volume of the container medium. Surprisingly, greater proportions of vermicomposts in the plant growth medium have not always improved plant growth.

In has been reported that vermicompost is at least 4 times more nutritive than cattle dung compost. In Argentina, farmers who use vermicompost consider it to be seven times richer than conventional composts in nutrients and growth promoting values. It is reported that exclusive application of vermicompost at the rate 25 quintal/ha in farm wheat crops supported yield better than chemical fertilizers.

It was 40 Q/ha on vermicompost and 34.2 Q/ha on chemicals. And when same amount of agrochemicals were supplemented with vermicompost the yield increased to about 44 Q/ha which is over 28% and nearly 3 times over control. On cattle dung compost applied at the rate 100 Q/ha (4 times of vermicompost) the yield was just over 33 Q/ha.

Application of vermicompost had other agronomic benefits. It significantly reduced the demand for irrigation by nearly 30-40%. Test results indicated better availability of essential micronutrients and useful microbes in vermicompost applied soils. Most remarkable observation was significantly less incidence of pests and disease attacks in vermicompost applied crops.

Some Significant Properties of Vermicompost of Great Agronomic Values:

(i) High Levels of Bio-Available Nutrients for Plants:

Vermicompost contains most nutrients in plant-available forms such as ‘nitrates’ (N), ‘phosphates’ (P), ‘soluble’ potassium (K), and magnesium (Mg) and ‘exchangeable’ phosphorus (P) and calcium’ (Ca) (70 and 73). Vermicomposts have large particulate surface areas that provide many micro-sites for microbial activities and for the strong retention of nutrients.

(ii) High Level of Beneficial Soil Microorganisms Promoting Plant Growth:

Vermicomposts are rich in ‘microbial population and diversity’, particularly ‘fungi’, ‘bacteria’ and ‘actinomycetes’. It has been found that the total bacterial count was more than 10¹⁰ per gram of vermicompost.

It included Actinomycetes, Azotobacter, Rhizobium, Nitrobacter and phosphate solubilizing bacteria which ranged from 10²-10⁶ per gm of vermicompost. The PSB has very significant role in making the essential nutrient phosphorus (P) ‘bio-available’ for plant growth promotion.

It has been also found that vermicompost prepared from cow-dung exhibited higher abundance of microbial population compared to vermicompost prepared from municipal solid wastes (MSW). The total bacterial count was 73 × 10⁸, the cellulolytic fungi were 59 × 10⁶ and the nitrogen-fixing bacteria were 18 × 10³.

It was least in vermicompost obtained from MSW. The total bacterial count was 16 × 10⁸, the cellulolytic fungi were 21 × 10⁶ and the nitrogen-fixing bacteria were 5 × 10³. Application of lime in the substrate enhanced the population of all above mentioned microbes irrespective of the substrates used for vermicomposting.

Plant growth promoting bacteria (PGPB) directly stimulates growth by nitrogen (N) fixation, solubilization, of nutrients, production of growth hormones such as 1- aminocyclopropane-1-carboxylate (ACC) deaminase and indirectly by antagonizing pathogenic fungi by production of siderophores, chitinase, (3-1, 3-glucanase, antibiotics, fluorescent pigments and cyanide.

Microbes, including bacteria, fungi, actinomycetes, yeasts and algae, also produce ‘plant growth regulators’ (PGRs) such as ‘auxins’, ‘gibberellins’, ‘cytokines’, ‘ethylene’ and ‘ascorbic acids’ in appreciable quantities and as their population is significantly boosted by earthworms large quantities of PGRs are available in vermicompost.

(iii) Rich in growth hormones: Biochemical Stimulating Total Plant Growth:

Researches show that vermicompost further stimulates plant growth even when plants are already receiving ‘optimal nutrition’. Vermicompost has consistently improved seed germination, enhanced seedling growth and development and increased plant productivity much more than would be possible from the mere conversion of mineral nutrients into plant- available forms.

It is reported that vermicompost contained growth promoting hormone ‘auxins’, ‘cytokinins’ and flowering hormone ‘gibberellins’ secreted by earthworms.

(iv) Rich in Humic Acids: Biochemical Promoting Root Growth and Nutrient Uptake:

The growth responses of plants from vermicompost appears more like ‘hormone-induced activity’ associated with the high levels of humic acids and humates in vermicompost rather than boosted by high levels of plant-available nutrients.

It has been reported that humic acids enhanced ‘nutrient uptake’ by the plants by increasing the permeability of root cell membrane, stimulating root growth and increasing proliferation of ‘root hairs’.

(v) Vermicompost is Free of Pathogens:

A combination of thermo-composting and vermicomposting for a period of 21 days produced compost with acceptable C: N ratio and good homogeneous consistency of a fertilizer. Vermicomposting leads to greater reduction of pathogens after 3 months upon storage.

(vi) Vermicompost is Free of Toxic Chemicals:

Several studies have found that earthworms effectively bio-accumulate or biodegrade several organic and inorganic chemicals including ‘heavy metals’, ‘organochlorine pesticide’ and ‘polycyclic aromatic hydrocarbons’ (PAHs) residues in the medium in which it inhabits.

(vii) Vermicompost Protects Plants against various Pests and Diseases:

There has been considerable evidence in recent years regarding the ability of vermicompost to protect plants against various pests and diseases either by suppressing or repelling them or by inducing biological resistance in plants to fight them or by killing them through pesticidal action.

(viii) Induce Biological Resistance in Plants:

Vermicompost contains some antibiotics and actinomycetes which help in increasing the ‘power of biological resistance’ among the crop plants against pest and diseases. Pesticide spray was significantly reduced where earthworms and vermicompost were used in agriculture.

(ix) Repel Crop Pests:

Worm’s varmicastings sometimes repel hard-bodies pests. Significant decreases in arthropods (aphids. buds, mearly bug, spider mite) populations and subsequent reduction in plant damage, in tomato, pepper and cabbage trails was recorded with 20% and 40% vermicompost additions.

(x) Suppress Plant Disease:

Use of vermicompost in crops inhibited the soil-born fungal diseases. Significant suppression of plant-parasitic nematodes in field trials with pepper, tomatoes, strawberries and grapes was found.

The scientific explanation behind this concept is that high levels of agronomically beneficial microbial population in vermicompost protects plants by out-competing plant pathogens for available food resources i.e. by staving them and also by blocking their excess to plant roots by occupying all the available sites. However the aqueous extracts of vermicomposts depress soil-borne pathogens and pests.

Factors Responsible for the Nutritional Quality of Vermicompost:

The nutritional quality of vermicompost is determined primarily by the type of the substrate (raw materials) and species of earthworms used for composting, along with microbial inoculants, liming, aeration, humidity, pH and temperature. Cattle dung has been found to yield most nutritive vermicompost when composted by Eisinea fetida.

The application of lime at the rate of 5 gm./kg of substrate and ‘microbial inoculation’ by suitable ‘cellulolytic’, ‘lignolytic and ‘N-fixing’ strains of microbes not only enhance the rate of vermicomposting but also results into nutritionally better vermicompost with greater enzymatic (phosphatase and urease) activities. An inoculation with N-fixing bacteria significantly increased the nitrogen’ (N) content of the vermicompost.

Liming generally enhance earthworm activities as well as microbial population. Earthworms after ingesting microbes into its gut proliferate the population of microbes to several times in its excreta (vermicast). It is therefore advantageous to use beneficial microbial inoculants whose population is rapidly increased for rapid compositing and also better compost quality.

1. Total Nitrogen:

Cow dung recorded maximum increase in nitrogen (N) content (275%) followed by MSW (178%), grass (153%) arid aquatic weed (146%) in their resulting vermicomposts over the initial values in their raw materials. And this was even without liming and microbial inoculation.

Application of lime without microbial inoculation, however, increased N content in the vermicompost from 3% to 12% over non-limed treatment, irrespective of substrates used.

2. Total Phosphorus and Potassium:

Similarly, the vermicompost prepared from cow dung had the highest total phosphorus (12.70 mg/g) and total potassium (11.44 mg/g) over their initial substrate followed by those obtained from aquatic weeds, grasses and MSW.

This was also irrespective of time application and microbial inoculation. Among the microbes inoculated for vermicomposting, Bacillus polymyxa a free-living N-fixing bacterium was most effective in increasing total phosphorus (11-22%) in the vermicompost after liming.

3. Humic Acid:

It was highest in vermicompost prepared from cow dung (0.7963 mg/g), followed by those from grasses (0.6147 mg/g), aquatic weeds (0.4724 mg/g) and MSW (0.3917 mg/g). And this was without liming and microbial inoculation. However, microbial inoculation again increased humic acid contents in vermicompost from 25% to 68% depending upon the substrate used.

Inoculation by Phanerochaete chrysoporium recorded highest humic contents without liming as compared to other inoculants. But under limed condition, inoculation by B. polymyxa was most effective in increasing humic acid contents irrespective of substrates used for vermicomposting.

4. Phosphatase Activity:

Vermicompost obtained from cow dung showed the highest ‘acid phosphatase’ (200.45 µg p-nitro-phenol/g/h) activities followed by vermicompost from grasses (179.24 µg p-nitro-phenol/g/h), aquatic weeds (174.27 µg p-nitro-phenol/g/h) and MSW (64.38 µg p-nitro-phenol/g/h).

The ‘alkaline phosphatase’ activity was highest in vermicompost obtained from aquatic weeds (679.88 µg p-nitro-phenol/g/h) followed by cow dung (658.03 µg p-nitro-phenol/g/h), grasses (583.28 µg p-nitro-phenol/g/h) and MSW (267.54 µg p-nitro-phenol/g/h).