In recent years, in an overzealous pursuit of organic farming with concern for protecting the environment, use of fertilizers and agricultural chemicals has been discouraged, and it is advocated to supply all the plant nutrients through organic manure only. Total organic farming may be a desirable proposition, but is not feasible to practice and sustain at high levels of crop production in modern commercial agriculture as we do not and cannot have enough organic manure to meet the requirements for all our arable lands.
Total organic farming would be possible only under subsistence farming as practiced in our country under traditional low-productive agriculture a few decades back. It might also be possible under certain special situations like horticultural farming where sufficient organic manures like FYM or composts would be available for recycling and where the consumer would be ready to pay extra premium prices for the ‘green products’ to compensate for their comparatively lower productivity and higher cost of production.
The food security of our ever-growing population has been made possible in our country by increasing foodgrain production from about 50 million tonnes in 1950 to more than 220 million tonnes now, by raising high-yielding varieties of crops, adopting Integrated Nutrient Management practices involving both manures and fertilizers, and controlling pests and diseases through Integrated Pest Management practices. At this juncture, it would be unwise and un-remunerative to cultivate crops without fertilizers and using manures alone. What is needed is a judicious combination of organic manures and fertilizers and not exclusive use of either.
Sources of nutrients
Plants absorb all the nutrients only in inorganic ionic forms, irrespective of the sources through which they are supplied. They cannot differentiate between the nutrients supplied through manures or fertilizers.
The nutrients supplied through organic and inorganic sources do not function differently within the plant. The nutrients from the organic and inorganic sources differ only in their relative availability for the crop uptake. The nutrients from the fertilizers are readily available as most of these are in water-soluble forms. The nutrients supplied through the organic manures become available for the crop uptake slowly but for longer duration due to the slow decomposition rate of the manure and consequent gradual release of the nutrients, through mineralization into the labile pool. Once released, nutrients from both the fertilizers and manures behave similarly in the soil, passing through the usual chemical and biochemical transformation reactions.
Quality of crop produce
It is true that the quality of the agricultural produce, particularly horticultural produce like flowers, vegetables and fruits, improves when the nutrients are supplied through organic manures than in the forms of fertilizers. This is because of the supply of all the growth principles like enzymes, hormones, growth regulators, etc., besides all the essential plant nutrients from the manures. As a result, the metabolic functions are regulated more effectively, resulting in better synthesis of proximate constituents like carbohydrates, proteins, fats, oils etc., leading to improvement in the quality of the produce.
Fertilizers supply one or a few nutrients only and not the growth principles like enzymes, vitamins and growth regulators, which are essential for quality of the produce. This is the reason for the better quality of the produce obtained with the application of manures and not due to differences in the nature and properties of the nutrients supplied through manures and fertilizers.
The distortion in soil fertility and deterioration in soil health are due to improper and indiscriminate use of fertilizers, exclusively supplying a few essential elements like nitrogen, phosphorus and potassium only, irrespective of the status and availability of these nutrients in the soil. These lopsided fertilization practices have led to imbalances in the status and availability of plant nutrients due to excess of certain nutrients and deficiencies of some others. This distortion in soil fertility can be corrected only with proper and judicious manure – fertilizer schedules based on soil fertility evaluation results.
Question of scale
Intensive agriculture on commercial high-productive scale cannot be sustained for long through total organic farming. This is because yield levels come down drastically without fertilizers, as the demands of the crops for certain nutrients like nitrogen, phosphorus and potassium in comparatively higher amounts cannot be met with organic manures alone. Although the indiscriminate use of fertilizers and chemicals has a potential for polluting the environment, it does not warrant exclusion of fertilizers altogether from the soil fertility management programmes, as the consequences can be disastrous.
Integrated Soil Fertility Management using manures, fertilizers and bio-fertilizers will facilitate restoration, improvement and maintenance of soil fertility, which will guarantee agricultural production at high levels with high-quality produce as well. Agriculture at high levels of productivity can be sustainable only through such integrated ways using manures, fertilizers and bio-fertilizers in judicious combinations. This will also safeguard the environment and natural resources from being polluted and exhausted.
The philosophy of sustainable agriculture will become a bitter irony, if fertilizer use is reduced or excluded in the name of quality improvement of produce or environment protection, as such exclusion would lead to subsistence farming over the years in the near future. So, we must rediscover our green renaissance through integrated soil fertility management practices involving manures, fertilizers and bio-fertilizers to ensure and sustain environment-friendly high-productive, good quality agriculture not only now but in future too. Neither organic nor inorganic but ISFM (Integrated Soil Fertility Management) must be the set rule of sustainable high-productive, good-quality agriculture to ensure food security.
(The article is the personal view of Dr. K. Kumaraswamy, formerly Professor of Soil Science & Agricultural Chemistry, Tamil Nadu Agricultural University, Coimbatore – 641 003, email: firstname.lastname@example.org)