Reclaiming Simple Clod

Published: Friday 31 January 2003

Reclaiming Simple Clod

-- (Credit: N Thiagarajan)Soils are a very slow renewable resource. To reclaim them requires, above all, a long-term plan. With falling productivity, the realisation has sunk in that soils cannot be blindly mined, and that humans cannot just plough through the ecology they interact with.

apply gypsum: Seven lakh ha of land in Punjab and Haryana have been reclaimed using techniques such as applying gypsum or lime to salt-affected soils, or cultivating salt-tolerant crops along with nutrient and water management. But these technologies are expensive. And it takes a long time to make the soil fertile. Besides, salinisation is not always reversible, even with major investments in drainage facilities.

manage nutrients: Scientists believe integrated nutrient management (farmyard organic manure used in combination with chemical fertilisers) is the best way to tackle micronutrient deficiency in soils (see diagram: Go with the flow). Experiments conducted by icar proved that use of npk fertilisers (in recommended quantities) combined with 10 to 15 tonnes of farmyard manure per ha could as much as triple yields obtained from nitrogenous fertilisers alone. The potential for rural compost alone is 600 million tonnes. Urban compost adds up to another 15 million tonnes and green manure about 30 million tonnes. Less than 50 per cent of this potential has been harnessed so far.

microbes and earthworms: There is a teeming, if invisible, army of microbes in the soil and subsoil that support plant growth and recycle nutrients; an estimated 100 million bacteria, and 10,000 different species, in every gram of arable soil. The top 15 centimetres may contain as much as 4,000 kg of live microorganisms. These process organic manure twice their weight, making nutrients available to plants in readily usable form. However, their contribution has not received the kind of attention it ought to have.

There are also other organisms that help improve soil quality. Earthworms, for instance, function as 'underground farmers', turning the soil over. Just one acre of land could be home to over a million earthworms, eating about 10 tonnes of leaves, stems and dead roots a year and ploughing 40-odd tonnes of soil. This is also the basis of a process called vermiculture, where worms are used to decompose organic waste into nutrient-rich vermicompost. Vermicompost improves soil structure, texture and aeration, as well as its water-holding capacity.

what about sludge? In India, farmers in and around cities and towns apply sewage sludge to agricultural land, especially for growing vegetables and other horticultural crops. However, there has been some controversy surrounding the use of sludge, especially in the us. (see: 'Fresh evidence', Down To Earth; Vol 11, No 16; January 15, 2003) Waste materials from households and industrial units have heavy metals -- such as lead, chromium, cadmium and arsenic -- in toxic levels. There could also be pharmaceutical wastes, or pathogens. There's a long way to go before this application finds use as a source of organic manure. As Dilip K Biswas, chairperson, Central Pollution Control Board, puts it dryly, "We do not have any standards for sewage sludge for land application."

or sequestration? The spectre of climate change, and global warming, has brought to the fore the issue of soil carbon sequestration. It is now touted as a two-pronged solution: it could make up for loss of soil carbon over years of land degradation; and help reduce greenhouse gases. Soils, through inorganic chemical reactions, convert atmospheric carbon dioxide into soil inorganic compounds such as calcium and magnesium carbonates. Plants also absorb carbon directly from the atmosphere through photosynthesis. Subsequently, some of this plant biomass is indirectly sequestered as soil organic carbon when the plant decomposes.

biggest hope: Perhaps the biggest hope is a re-recognition of the value of traditional farming systems, and creating what may be called farming eco-technologies that combine modern methods with traditional practices (see box: B Vishwanath's dream come true?).

but then... It is intriguing that the hundreds of scientific conferences and fora, which have discussed eroding soil fertility in India, have had little influence on government policies. Part of the problem is that scientists are not involved in the fertiliser or agriculture policy-making process in India. These policies are influenced by various pressure groups, such as the fertiliser industry and groupings of big farmers.

Soil scientists unanimously aver that if soil health, and by implication crop yield, has to improve, the focus has to shift from crops to soil. But who will make the bureaucrats understand this? Much research is available, and even more data. But not a single figure can match the intentions of politicians, who only like short-term experiments with soiling democracy. Isn't it execrable that scientists have not been involved in any serious macro-level planning to restore depleted soil fertility?

Recently, the nbss-lup has come out with a soil map of India, the first-ever. It took 1,500 personnel over 10 years to prepare; and samples were taken every 10 km. The survey accounts for diverse factors, such as physical, chemical and biological properties, soil depth, particle size, soil temperature, and climate. Is the Union Cabinet aware of this? Does it plan to use it for the country's better future?

But then, B Vishwanath no longer delivers the presidential address at the Indian Science Congress.

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