P N TAKKAR former director of the Indian Institute of Soil Science, Bhopal, and currently principal scientist at the Indian Agricultural Research Institute, New Delhi, has been working on micro and secondary nutrients in soil and plant nutrition for the past 30 years. He has primarily focussed on identifying nutrient deficiency disorders in different soils and crop conditions. He spoke to AMIT NAIR on the nutrient deficiencies and toxicity of soil in India
Why are soil micronutrients important in agriculture?
Any country can be held to ransom if it does not have food security. We have to take appropriate measures to see that we are self-reliant on the food situation. The soil contains different types of elements which are essential for the development of a healthy plant. Soil overuse -- when one practices intensified agriculture of raising more crops per unit-time and over dependence on high analysis fertilisers -- depletes the micronutrient reserves in the soil. Such soil in the near future will fail to sustain agricultural produce.
How severe is the micronutrient problem in India?
In India, the depletion of soil micronutrient is a cause for concern. Most soils in India are generally poor in fertility as they have consistently been depleted of their nutrient resources due to continuous cultivation.The micronutrient deficiencies of zinc, iron, manganese and boron are widespread and are associated with specific soils or soil cropping systems. This has resulted in the soil becoming a poor food crop producer.
Which are the states that are severely affected by this problem?
The states severely affected include Punjab, Haryana, Bihar, Uttar Pradesh, Madhya Pradesh, Gujarat, Tamil Nadu and Andhra Pradesh. In most of these states micronutrient deficiencies are widespread.
How is the present practice of farming responsible for micronutrient depletion?
The national thrust has been on maximisation of food production to feed its expanding population. This has resulted in the depletion of micronutrient reserves. Modern agriculture, which relies heavily on intensive cultivation and use of fertilisers, has depleted the micronutrient reserves of the soil. Unless immediate steps are taken to replenish the micronutrient reserves, the soil will lose all its fertility.
Has the use of fertilisers and pesticides or both aggravated the problem?
The improper or imbalanced use of fertilisers has worsened the problem at many places. The increasing use of fertilisers generally devoid of micronutrients has brought about the problem related to micronutrient deficiencies by depleting the resources in the soil. Although fertilisers are essential for increasing production, they should be used very judiciously.
A number of extensive experiments on manuring and fertilisation have resulted in the depletion of the available micronutrient status of soils, particularly zinc. Pesticides have nothing to do with aggravating the micronutrient problem.
What are the factors that affect the soil micronutrient depletion?
A few important factors which affect the soil micronutrient status are extensive cultivation of fertiliser-responsive high-yielding varieties on marginal soil. Large-scale deforestation has also led to the reduction of organic matter and depletion of soil micronutrient. In addition, long-term application of nitrogenous and phosphatic fertilisers and intensive cropping (raising of more crops per unit time involving dependence of high analysis fertilisers) have played a major role in depleting the soil micronutrient levels.
What is the impact of soil micronutrient on animal and human health?
One should be clear that animals and humans depend largely on plants for their mineral requirements and the plants in turn depend on soil micronutrients for their growth and yield. Although, these micronutrients are required in extremely small quantities, they are nevertheless as important as macronutrients. A large number of these micronutrients are very essential to animals and humans for their growth and reproduction since these micronutrients are building blocks for all life forms. A deficiency in iron and zinc is common in humans and zinc and copper in animals.
What should be the strategy to minimise micronutrient depletion in soils?
One alternative is growing micronutrient-efficient crops and their cultivars to minimise depletion of micronutrients.
Do you think the measures undertaken by the government are adequate ?
The government has taken a few important steps but more needs to be done. Firstly, the government has to set up coordinating centres in all the states to study the soil micronutrient problems and bring about corrective measures.
However, there is also a need to strengthen the soil testing laboratories with experts and modernise equipment. Polyclinics should be set up for providing micronutrient advisory services to the user for improving the soil productivity along with other services.
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