Tips on improving soil fertilty - Through application of Vermicompost

Vermicomposting

TYPES OF EARTHWORM

The most common types of earthworms used for vermicomposting are brandling worms (Eisenia foetida) and redworms or red wigglers (Lumbricus rubellus). Often found in aged manure piles, they generally have alternating red and buff-colored stripes. They are not to be confused with the common garden or field earthworm (Allolobophora caliginosa and other species). Although the garden earthworm occasionally feeds on the bottom of a compost pile, they prefer ordinary soil. An acre of land can have as many as 500,000 earthworms, which can recycle as much as 5 tons of soil or more per year. Redworms and brandling worms, however, prefer the compost or manure environment. Passing through the gut of the earthworm, recycled organic wastes are excreted as castings, or worm manure, an organic material rich in nutrients that looks like fine-textured soil.

WHAT IS VERICOMPOSTING?

Vermicompost contains not only worm castings, but also bedding materials and organic wastes at various stages of decomposition. It also contains worms at various stages of development and other microorganisms associated with the composting processing. Earthworm castings in the home garden often contain 5 to 11 times more nitrogen, phosphorous, and potassium as the surrounding soil. Secretions in the intestinal tracts of earthworms, along with soil passing through the earthworms, make nutrients more concentrated and available for plant uptake, including micronutrients. Redworms in vermicompost act in a similar fashion, breaking down food wastes and other organic residues into nutrient-rich compost. Nutrients in vermicompost are often much higher than traditional garden compost (see table 1).

Table 1. Chemical characteristics of garden compost and vermicompost, 1994.

Parameter* Garden compost1 Vermicompost2

pH 7.80 6.80
EC (mmhos/cm)** 3.60 11.70
Total Kjeldahl nitrogen(%)*** ````````````````0.80 1.94
Nitrate nitrogen (ppm)**** 156.50 902.20
Phosphorous (%) 0.35 0.47
Potassium (%) 0.48 0.70
Calcium (%) 2.27 4.40
Sodium (%) < .01 0.02
Magnesium (%) 0.57 0.46
Iron (ppm) 11690.00 7563.00
Zinc (ppm) 128.00 278.00
Manganese (ppm) 414.00 475.00
Copper (ppm) 17.00 27.00
Boron (ppm) 25.00 34.00
Aluminum (ppm) 7380.00 7012.00
1Albuquerque sample 2Tijeras sample
*Units- ppm=parts per million mmhos/cm=millimhos per centimeter
** EC = electrical conductivity is a measure (millimhos per centimeter) of the
relative salinity of soil or the amount of soluble salts it contains.
*** Kjeldahl nitrogen = is a measure of the total percentage of nitrogen in the
sample including that in the organic matter.
**** Nitrate nitrogen = that nitrogen in the sample that is immediately available
for plant uptake by the roots.


Finished vermicompost should have a rich, earthly smell if properly processed by worms. Vermicompost can be used in potting soil mixes for house plants and as a top dressing for lawns. Screened vermicompost combined with potting soil mixes make an excellent medium for starting young seedlings. Vermicompost also makes an excellent mulch and soil conditioner for the home garden.


ANATOMY OF EARTHWORMS

The earthworm has a long, rounded body with a pointed head and slightly flattened posterior. Rings that surround the moist, soft body allow the earthworm to twist and turn, especially since it has no backbone. With no true legs, bristles (setae) on the body move back and forth, allowing the earthworm to crawl. The earthworm breathes through its skin. Food is ingested through the mouth into a stomach (crop). Later the food passes through the gizzard, where it is ground up by ingested stones. After passing through the intestine for digestion, whats left is eliminated. Earthworms are hermaphrodites, which means they have both male and female sex organs, but they require another earthworm to mate. The wide band (clitellum) that surrounds a mature breeding earthworm secretes mucus (albumin) after mating. Sperm from another worm is stored in sacs. As the mucus slides over the worm, it encases the sperm and eggs inside. After slipping free from the worm, both ends seal, forming a lemon-shape cocoon approximately 1/8 inch long. Two or more baby worms will hatch from one end of the cocoon in approximately 3 weeks. Baby worms are whitish to almost transparent and are 1/2 to 1 inch long. Redworms take 4 to 6 weeks to become sexually mature.

HOW TO CONSTRUCT A WORM BED/PIT

The beds can be either in the open (in the shade of a coconut groove like area) or in a covered area. Covered area is preferred for conducting all weather vermicomposting. The recommended depth of the pit should be 12 to 18 inches and not more. Keep the width of the bed at four feet max. Length of the bed may be decided to your convenience.

First layer of the bedding should be made of farm waste. Over the same, apply liberally fresh cow dung diluted in water. Over that surface add a layer of fresh cow dung. Again make a layer of farm waste. Sprinkle liberally the cowdung diluted in water. Keep on top another layer of fresh cow dung. Fill up the pit completely. Keep adequate moisture. The pit should be able to conserve moisture. Maintain the moisture of the bed. Moisture should be just adequate. Cover the top with some black cloth or dark coloured cloth. This will help in retaining the moisture. The worms also prefer darkness. You may cover the top with straw mulch too. This will also help in ventilation. You must be careful of pests, birds, etc that feed on the earthworm.

BEDDING MATERIALS

Bedding for bins can be made from shredded newspapers (non-glossy), computer paper, or cardboard; shredded leaves, straw, hay, or dead plants; sawdust; peat moss; or compost or aged (or composted) manure.. Grass clippings should be allowed to age before use because they may decompose too quickly, causing the compost to heat up. Bedding materials high in cellulose are best because they help aerate the bin so the worms can breathe. Varying the bedding material provides a richer source of nutrients. Some soil or sand can be added to help provide grit for the worms digestive systems. Allow the bedding material to set for several days to make sure it doesn’t heat up (and allow to cool before adding worms). The bedding material should be thoroughly moistened (about the consistency of a damp sponge) before adding the worms. Fill the bin three-quarters full of moist bedding, lifting it gently afterwards to create air space for the worms to breathe and to control odors.

ADDING THE WORMS

Under optimum conditions, redworms can eat their own weight in food scraps and bedding in one day. On the average, however, it takes approximately 2 pounds of earthworms (approximately 2,000 breeders) to recycle a pound of food waste in 24 hours. The same quantity of worrms requires about 4 cubic feet of bin to process the food waste and bedding(1 cubic foot of worm bin/500 worms). Composting worms can be purchased from dealers Add worms to the top of the moist bedding when they arrive. The worms will disappear into the bedding within a few minutes.

CONTROLLING TEMPERATURE AND MOISTURE IN THE BIN/PIT

Redworms can survive a wide range of temperatures (40-80F), but they reproduce and process food waste at an optimum bedding temperature range of 55-77F. The worms should never be allowed to freeze. The bin/pit contents should be kept moist but not soaked. Do not allow rainfall to run off a roof into the bin/pit. This could cause the worms to drown. A straw covering may be needed in exposed sites to keep the bin/pit from drying out during hot summer weather.

MAINTAINING THE BIN/PIT

Food scraps can be continually added to the bin for up to 2 to 3 months, or until you notice the bedding material disappear. When the bedding disappears, harvest the worms and finished compost, then refill the bins with new bedding material. Overloading the bin with food wastes can result in foul odors. If you notice these odors, stop adding the waste until the worms have a chance to catch up. Overly moist food waste and bedding also cause odors. To relieve this roblem, fluff up the bedding to add air and check the drainage holes. As a general rule of thumb, keep the bedding material moist, but never soggy. Make sure the food waste is buried properly in the bedding. Exposed food wastes can attract fruit flies, house flies, and other pests. Keeping the bin/pit covered with straw or moist dark cloth also deters these pests. Garden centipedes can be a problem in the worm bin/pit, especially outside. These predators should be destroyed. Overly wet beds also can attract the earthworm mite, which may cause the worms to stop eating.

HARVESTING THE COMPOST AND WORMS

Once the pit/bin is ready for harvest, collect few kilos of fresh cow dung and keep it on the top of the bed in two or three places. All the worms will move towards the fresh dung and will stay underneath the fresh dung. Collect these worms and move them to the new pit/bin. Do this process a few times till you are satisfied that you have collected all or a significant majority of the worms.

The compost also can be placed in small piles on a tarp in the sun (or under bright lights inside). Because worms don’t like light, they will wiggle to the bottoms of the piles. After waiting 10 minutes, remove the upper inch or more of finished compost from each pile until you run into the worms. Allow the worms to again wiggle to the bottom of the pile and repeat the process. Combine what is left of the small piles into one big pile and again repeat the process. You should eventually end up with a pile of finished compost for your use. You will also get a ball of worms which you can reintroduce into the new bed/pit/bin.

You can directly apply the vermicompost on the top soil. This will certainly enrich the soil and enhance its fertility very substantially. Ofcourse, if you buy vermicompost from manufaturers and apply it may not be cost effective. As farmers we should try our best to produce items like vermicompost ourselves as all the inputs are available in the farm itself.