On the basis of concentration of nutrients, manures can be grouped into-1. Bulky Organic Manures 2. Concentrated Organic Manures.
1. Bulky Organic Manures:
Contain small percentage of nutrients and they are applied in large quantities. FYM, Compost and Green manure are the most important and widely used bulky organic manures.
I. Farm Yard Manure (FYM):
Decomposed mixture of dung and urine of farm animals along with litter and left over material from roughages or fodder fed to the cattle. FYM contains 0.5%N, 0.2% P2O5 and 0.5% K2O. Urine contains 1%N & 1.35%K2O. N present in urine is mostly in the form of urea which is subjected to volatilization losses. Size of trench- 6-7.5m long, 1.5-2.0m wide and 1m deep. Heaped upto height of 45-60 cm above the ground level, dome shaped and plastered with cowdung earth slurry.
The manure becomes ready for use in about 4 – 5 months after plastering. Chemical preservatives are used to reduce losses and enrich FYM. e.g. – gypsum, kainite, and superphosphate. Gypsum absorbs urine and prevents volatilization loss of urea and also adds Ca and S. Superphosphate also acts similarly and increases ‘P’ content.
Bacteria and Actinomycetes play active role in decomposition. 60-70% moisture in the initial stage and 30-40% moisture in decomposed manure (ready to use) as well as 50-60° C temperature under the heap are favourable for the activities of these micro- organisms.
Generally 10-20 tonne well decomposed FYM per ha is applied but > 20 tonne FYM /ha in case of fodder grasses and vegetables, at least 15 days before the sowing to avoid immobilisation of N. Entire amount of nutrient is not available immediately.
About 30% N, 60-70% P2O5 and 70% K2O are available to the first crop.
FYM is the most commonly used organic manure in India. One tonne of cattle dung can supply only 2.95kg. N, 1.59kg P2O5 and 2.95kg of potash.
Hot and Cold Manure:
The manure obtained from the excreta of horses and sheep is called hot manure in temperate countries where- as pig and cattle manure is called cold manure due to comparatively less vigorous decomposition and less rise in temp in manure.
Short and Long Manure:
Decomposed manure that has lost the structure of the original materials is called short manure while the fresh manure having pieces of straw and other materials is called long manure.
There is profuse fungal growth on the surface of moist manure, giving it an ashy grey appearance. It is referred to as fire fanging.
Composting is the process of reducing vegetable and animal refuse (rural or urban) except dung to a quickly utilisable condition for improving and maintaining soil fertility and decomposed material is called compost. Compost is like well- decomposed cattle manure in general appearance, more powdery and lighter in colour.
Ordinary compost can be enriched with N and P through Azotobacter and superphosphate respectively. When superphosphate is used during compost making it is called super compost and compost prepared by using N-fixing bacteria is called Azo compost. Azo compost is the cheapest source of N among all organic manures (N → 1.5%).
Superphosphate or rock- Phosphate @ 10-15kg/tonne of raw material is applied at the initial stage of filling the compost pit. Size of pit is about the same of FYM.
The compost made from farm waste like sugarcane trash, paddy straw, weeds and other plants and other waste is called Farm-Compost (0.5% N, 0.15% P2O5, 0.5% K2O). Farm compost prepared by Bangalore method contains 0.80 -1.24% N, 0.40-0.59% P2O5 and 2.0-3.3% K2O.
The compost made from town refuses like night soil, street sweepings and dustbin refuse is called Town compost (1.4%N, 1% P2O5, 1.4% K2O).
III. Night Soil (or Poudrette):
Night soil is human excreta, both solid and liquid. It contains 5.5% N, 4.0% P2O5 2.0%. K2O)
The dehydration of night soil, as such or after admixture with absorbing materials e.g. soil, ash, charcoal & sawdust produces a poudrette that can be used easily as manure. Poudrette contains 1.32% N, 2.8% P2O5 & 4.1% K2O.
IV. Sewage and Sludge:
The solid portion in the sewage is called sludge and liquid portion is sewage water. Both the components are separated and are given a preliminary fermentation and oxidation treatments to reduce bacterial contamination and offensive smell, otherwise soil quickly becomes ‘sewage sick’ owing to the mechanical clogging by colloidal matter in the sewage and the development of anaerobic organisms which not only reduce the nitrates already present in the soil but also produce alkalinity.
These defects can be removed by thoroughly aerating the sewage in the settling – tank by blowing air through it. The sludge that settles at the bottom in this process is called activated sludge’ (3-6% N, 2% P2O5 & 1% K2O).
V. Sheep and Goat Manure:
It contains 3% N, 1% P2O5 & 2% K2O.
It is applied to the field in two ways:
(i) Sweeping of sheep and goat sheds are placed in pits for decomposition and it is applied later to the field.
(ii) Sheep penning, wherein sheep and goats are allowed to stay overnight in the field and urine and faecal matter is added to soil.
VI. Poultry Manure:
3.03% N, 2.63% P2O5 & 1.4% K2O, Litter is the straw, peat, sawdust, dry leaves etc. are used as bedding material for farm animals and birds. It absorbs urine and faeces voided by animals and birds.
VII. Green Manure:
Green undecomposed plant material used as manure is called green manure.
It is obtained in two ways:
(i) By growing green manure crops in the field and incorporating it in its green stage in the same field. It is called green manuring.
(ii) Green leaf manuring is the application of green leaves and twigs of trees, shrubs and herbs collected from elsewhere especially waste land fields, bunds & forests to the field. Forest tree leaves are the main sources for green leaf manure e.g. neem, mahua, Glyricidia, Karanji (Pongamia) sesbania, subabul, Indigo etc.
Lentil is used in Kashmir for green manuring in paddy. Sunnhemp is most outstanding green- manure, well suited to almost all parts of country. Dhaincha does well in alkaline and waterlogged soils. Berseem for orchards and irrigated crops of cotton and sugarcane.
Plants at flowering stage contain the greatest bulk of succulent organic matter with low C:N ratio. The incorporation of the green manure crop at this stage allows a quick liberation of N in available form. The fertilizer value of the legume crop can be increased by manuring it with superphosphate (@100kg/ha). It increases ‘p’ content of green manure crops and thus converting an inorganic fertilizer into an organic manures. It has residual affects also.
Green manuring gives 60-80 kg N/ha on an average.
Green manuring crops having stem nodulation are:
(a) Sesbania rostrata – It is the fastest N2– fixing plant @ 100-285 kg N/ha in 45-55 days.
(b) Aeschynomene afraspera
2. Concentrated Organic Manures:
Concentrated organic manures have higher nutrients than bulky organic manures.
1. Bird guano- The excreta and dead remains of the birds. 7-8% N, 11-14% P2O5 & 2-3% K2O.
2. Fish guano – The refuse left over after the extraction of oil from the fish in factories, is dried in paved yards and used as manure 7% N & 8% P2O5.
3. Fish manure – 4-10% N, 3-9% P2O5 & 0.3-1.5% K2O
4. Raw bonemeal – 3-4% N, 20-25% P2O5
5. Steamed bone meal – 1-2%N, 25-30% P2Os
6. Blood meal – 13-20% N, rich in Iron and its application gives a deep rich colour to the foliage, much appreciated by ornamental gardeners.
7. Meat meal/meat guano/tankage – 8-9% N and 7% P2O5.
8. Calcined bone – 37% P2O5
9. Oilcakes – Sunflower cake – 7.8% N, Groundnut cake – 7.2% N, Cotton cake – 6.5% N.
Non-edible oilcakes are used as manures especially for horticultural crops (edible fed to cattle). Nutrients present in oilcakes, after mineralisation, are made available to crops 7-10 days after application.
Oilseed cakes need to be well powdered before application for even distribution and quicker decomposition. Neem cake reduces nitrification means acts as nitrification Inhibitor.