Organic Manure, Green Manure, and Biochar: Improving Soil Structure – Part I
Introduction:
In many villages, farmers are noticing gradual changes in the condition of their fields. Soil that was once relatively easy to plough is becoming hard and cloddy. After the first rain or irrigation, water sometimes remains on the surface instead of moving into the soil. When the field is ploughed, large clods are often seen.
There is another change that farmers frequently talk about. Earlier, a normal dose of fertiliser could produce good crop growth, but in some fields the same fertiliser dose does not give the expected response. Farmers may apply additional urea or other fertilisers. Yet the crop can still appear pale and the yield may not improve.
These observations should make us look beyond fertilisers alone and focus on the condition of the soil.
Soil is much more than the medium in which a crop grows. It contains organic matter, microorganisms, earthworms, air and water. These components work together to maintain soil structure and support healthy root growth. Continuous cultivation, residue burning, inadequate addition of organic matter and imbalanced fertiliser use can gradually affect these properties.
The situation, however, is not irreversible. Soil health can be improved with regular management. Farmers do not always need expensive inputs or complicated technologies. Some simple practices, when adopted according to local soil and crop conditions, can help improve soil structure, nutrient cycling and water management.
Based on field observations and agricultural experience, four practical approaches are discussed here: proper use of well decomposed farmyard manure, green manuring, inclusion of pulse crops in the cropping system, and appropriate use of biochar.
1. Proper Use of Well Decomposed Farmyard Manure
Farmyard manure is one of the oldest sources of organic matter available to farmers. However, the quality and stage of decomposition of manure are important.
One common practice is to remove fresh dung from the cattle shed and apply it directly to the field. While this may appear convenient, fresh manure is not always the best option for immediate field application.
Why should fresh manure be avoided?
Fresh manure contains relatively unstable organic materials. Depending on its composition and the soil conditions, its decomposition can temporarily affect the availability of some nutrients. It may also contain weed seeds and other unwanted materials if it has not been properly composted.
Well decomposed manure, on the other hand, is generally easier to handle and provides a more stable source of organic matter.
What should good manure look like?
Well decomposed farmyard manure is generally dark brown to black, crumbly and relatively uniform in appearance. It should not have a strong smell of fresh dung.
Wherever possible, manure should be allowed to decompose properly before field application. A period of around four to six months can be used as a practical guideline, although the actual decomposition period depends on moisture, temperature, turning and the method used for preparation.
For field application, the quantity should be decided according to manure quality, soil condition and the nutrient requirement of the crop. As a practical farm-level recommendation, farmers may consider around 3–4 trolley loads of well decomposed farmyard manure per acre, subject to the size and capacity of the trolley.
Where vermicompost is available, it can also be used as a concentrated organic input. Around 1.5–2 tonnes per acre may be considered wherever appropriate, but the quantity should ideally be adjusted according to soil-test results and crop requirements.
Organic manure does more than supply nutrients. Regular addition of organic matter can improve soil aggregation, support microbial activity and help create better conditions for root growth. In heavier soils, improved aggregation can also support better movement of air and water.
The important point is not simply to add more manure every year. The quality, maturity, quantity and method of application all matter.
2. Green Manuring: A Low-Cost Way to Add Organic Matter
For farmers who have limited access to farmyard manure, green manuring can be a useful option.
Green manure crops are grown primarily to improve the soil rather than for harvesting grain. Crops such as dhaincha (Sesbania spp.) and sunnhemp are commonly used for this purpose.
If there is a suitable window between two main crops, green manure can be incorporated into the soil before it becomes too mature.
Which crop should be selected?
The choice depends on the local climate, available moisture, cropping system and duration of the fallow period.
Dhaincha is particularly useful in many parts of India because it grows relatively quickly under suitable moisture conditions and produces substantial biomass.
Farmers should use a seed rate appropriate for the crop and local recommendation. For dhaincha, approximately 12–15 kg seed per acre may be used as a practical range in suitable conditions, although recommendations can vary with seed quality and sowing method.
When should it be incorporated?
Timing is important.
Green manure should generally be incorporated while the plants are still relatively young and succulent, commonly around 45–50 days after sowing, depending on crop growth and local conditions. Incorporation can be done using a rotavator, harrow or suitable tillage implement.
If the crop is allowed to become too old and woody, decomposition may take longer and the immediate benefits may be reduced.
What does green manure contribute?
A well grown green manure crop adds a significant quantity of fresh biomass to the soil. The exact amount depends on crop growth, plant population, soil fertility, moisture and climate.
Leguminous green manure crops can also contribute nitrogen through biological nitrogen fixation. However, the nitrogen contained in the plant material does not become immediately available to the following crop in its entirety. A portion is released gradually as the organic material decomposes.
This gradual release is one reason green manuring can be useful as part of an integrated soil-fertility management programme.
The decomposition of organic residues can also influence nutrient cycling and, under suitable conditions, may improve the availability of some nutrients.
For farmers, the main advantage is simple: green manure converts sunlight, water and a short fallow period into organic biomass that can be returned to the soil.
Conclusion
Improving soil health is not a one-time activity; it is a continuous process that requires the regular addition and proper management of organic matter. Farmyard manure and green manuring are simple and locally available practices that can help rebuild soil organic matter, improve soil structure and support better nutrient cycling.
The quality and timing of these practices are as important as their quantity. Well-decomposed farmyard manure should be preferred over fresh manure, while green manure should be incorporated at the appropriate stage to ensure effective decomposition and nutrient release.
For Indian farmers, particularly those facing declining soil quality, water-related challenges and rising input costs, such practices can form an important part of an integrated soil-health management approach. However, their effectiveness depends on soil type, climate, crop, moisture availability and the overall farming system.
Organic manure and green manuring provide the foundation for rebuilding soil health. In the next part, we will explore how pulse crops and biochar can complement these practices and contribute further to improved soil structure, nutrient management and long-term soil sustainability.










































