Organic Content in Soil

Owing to the efforts under the Green Revolution wherein farmers adopted modern inputs and technology to increase production, India successfully avoided the spectre of food shortages. But this came at a cost in the form of overexploitation of natural resources, especially soil and water. The crisis is so extreme that it has brought the issue of sustainability these natural resources to the fore.

Significance of Organic Content in the Soil

About 58% of organic matter mass exists in the form of carbon. Soil organic carbon (SOC) is extremely important for agriculture because:

• Farmers may apply urea or di-ammonium phosphate, but it is adequate SOC levels will what ensure that the nitrogen and phosphorous from these chemical fertilisers would be bio-available to crops.
• Organic matter is the source of food for the microorganisms that help increase the porosity and aeration of soils.
• The soil’s moisture-holding capacity increases with higher carbon levels, thereby reducing water runoff.

Hence it can be said that there is a direct correlation between SOC levels and soil productivity and, by extension, the sustainability of agriculture. Further, there is a link between climate change as well.

Atmospheric carbon dioxide is stored in the form of SOC through the process of absorption in crop production and plant residue retention in soil. This sequestration of atmospheric carbon dioxide is a powerful mitigating measure for climate change.

Depleting Organic Content in the Soil

The sample testing results from the Centre’s Soil Health Card Scheme shows a dismal picture. The SOC levels were found to be very low in most parts of India. The soils in temperate climates have better carbon levels. But it was quite the opposite in hot and tropical atmospheric areas where the soils tend to lose carbon through decomposition (mineralisation) of plant residues. Rising temperatures from climate change have further aggravated the situation.

Soil Health Card Scheme

Soil Health Card (SHC) is an initiative of Department of Agriculture & Co-operation under the Ministry of Agriculture and Farmers’ Welfare and is being implemented through the Department of Agriculture of all the State and Union Territory Governments.

A SHC gives each farmer soil nutrient status of the holding and advice them on the dosage of fertilizers and also the needed soil amendments to maintain soil health in the long run.

Besides fertilizer recommendations and soil amendment required for the farm, the SHC contains  the status of his soil with respect to 12 parameters, namely N,P,K (Macro-nutrients) ; S (Secondary- nutrient) ; Zn, Fe, Cu, Mn, Bo (Micro – nutrients) ; and pH, EC, OC (Physical parameters).

The SHC is made available once in a cycle of 3 years and it indicate the status of soil health of a farmer’s holding for that particular period. The SHC given in the next cycle of 3 years will be able to record the changes in the soil health for that subsequent period.

Improving Organic Content of Soil

Cropping Pattern

Plants take in atmospheric carbon dioxide and convert it into food through photosynthesis process. Crops producing more aboveground and root mass contribute to long-term productivity by enhancing soil organic matter. A change in cropping patterns to ensure high SOC and long-term productivity, will not take place unless the desired alternative crops are remunerative. It requires an appropriate policy intervention including encouragement to set up agri-processing units for such crops, which in turn will make it profitable for farmers to grow them.

Residue Management

The aboveground mass remaining after harvesting of the grain and dried stalks must be returned to the soil as much as possible. This requires scientific crop residue management.

The crop residue when burnt gets converted into carbon dioxide. Burning of crop stubble has a negative impact not just on the environment and human health, but also on soil fertility. Farmers burn the leftover straw and stubble after harvesting of paddy mainly because of the narrow time window to prepare their fields for sowing the next wheat crop. Hence a strategy focused on both in situ and ex situ management of residue is necessary.

At present, the issue is being addressed through the subsidised provision of implements such as Happy Seeder, Super-Straw Management System attachment, mulcher and chopper-shredder. But all this is mostly in areas closer to the national capital. For sustainable farming and improving soil health, all the states must pitch in.

Organic Matter from External Sources

There is clear evidence that when nitrogen, phosphorus and potassium are used in conjunction with the farm yard manure, the fertiliser response ratio itself goes up with rising SOC levels.

Therefore the use of compost must be promoted and further building of vermicompost pits or ‘Nadep’ mud/clay brick tanks can be subsidised using from MGNREGA and other schemes. Even urban green waste and manure from sewage treatment plants can be returned to farm soils.

Crop Rotation

It is necessary to plant legumes, either as a summer or full replacement crop in the Kharif/rabi season in the rice-wheat system. Legumes have root nodules harbouring rhizobium bacteria that fix nitrogen from the atmosphere. This nitrogen helps in binding and in retaining carbon in the soil for a longer time.

But the Farmers are hesitant to cultivate pulses due to lack of a proper system of procurement at minimum support prices, unlike that for wheat and paddy. Inclusion of pulses in the public distribution system would go a long way in promoting the cause of soil health as well as nutritional security for our masses.

No-till Implements

No-till implements deserve a big push. Organic carbon is retained in large soil aggregates. Deep ploughing equipment that breaks these aggregates results in SOC loss, whether through runoff with water or evaporation as carbon dioxide.

Zero-till seed drills, Happy Seeders and Direct Seeded Rice machines will ensure minimal disturbance of aggregates and less depletion of organic matter.

Building Awareness

There is a need to launch a comprehensive awareness programme for enhancing the organic matter content of soils, with specified and time-bound targets.