May 29, 2009 Ludhiana
Paddy crop in Punjab suffers from the deficiencies of micronutrients, especially zinc and iron. This has been stated by Dr. J.S. Manchanda and Dr. D.S. Bhatti of PAU Department of Soils in their article published in the Progressive Farming. These scientists state that the deficiencies of essential nutrients have been on the rise in the crops due to intensive cropping that depleted the soil of Punjab of various nutrients.
Seventeen elements are considered essential for plant growth and these are divided into two groups, macro (carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium and sulphur) and micro-nutrients (zinc, iron, manganese, copper, molybdenum, boron, chlorine, and cobalt)', said the scientists adding that micro-nutrients are taken up by the plants in lesser amount than the macro ones. They said that zinc deficiency is confined to the soils having high pH, high calcium carbonate, high available phosphorus, low organic matter and irrigated with sodic waters while iron deficiency is a problem of highly permeable light texture soils high in pH and poor in organic matter. Farmers are generally taking care of the supply of macro-nutrients but ignore micro-nutrients thereby resulting in poor yield of crops under deficient conditions, they said. When a soil contains less than 0.6 kg available zinc and 4.5 kg available iron per acre is considered to be deficient in these nutrients. For knowing the nutrient status soil testing is important.
The symptoms of zinc deficiency in paddy start appearing at about 15-20 days after transplanting. First these appear on older leaves as light yellow spots in the inter-veinal areas and later the spots turn yellowish brown, in large, become rusty. The growth and yield of plants may be affected. Iron deficiency appears as inter-veinal chlorosis of new/young leaves. Later, the whole leaf turns yellow and under acute situation, leaves may undergo bleaching. Occasionally, radish spots may develop on the bleached area, said the scientists.
To manage zinc deficiency application of 25 kg of zinc sulphate heptahydrate (having 21 % zinc) or 16 kg of zinc sulphate monohydrate (having 33% zinc) per acre in deficient soils at the time of last puddling should be applied. Soil application of zinc proves better than foliar application, said they. The iron deficiency can be corrected by foliar application of 1% solution of ferrous sulphate. Although 2-3 sprays may be adequate, yet the number of sprays can be increased depending upon the severity of deficiency. The scientists mentioned that application of ferrous sulphate to soils along with zinc sulphate is not desirable. They suggest only foliar application of ferrous sulphate to mitigate iron deficiency. Further, prolonged ponding of water by making small plots can help overcome iron deficiency to some extent, said the scientists adding that incorporation of 40-50 days old green manure crop of dhaincha every year before transplanting can go a long way in reducing the occurrence of iron deficiency in rice.
Source: PAU, Ludhiana