The Critical Zinc Deficiency Levels in Indian Soils and Cereal Crops

A number of greenhouse experiments were conducted in which cereal crops were grown in pots of a wide range of Indian soils to which Zn was added. Levels of soil Zn extractable in DTPA were determined and related to the growth of these crops. DTPA extractable Zn was found to be a reliable predictor of the response of cereal crops to Zn added to the soils. Critical levels of Zn ranged from 0.38 to 2.00 mg/kg soil. Even on the same soil the range of critical limit for rice was the widest. The finding that a good reparation of Zn deficient and non-deficient soils could be obtained by using DTPA extractable critical Zn values has an important field application in that it provides a method of continuously monitoring the Zn status of different soil types and for predicting response of cereal crops to Zn fertilization. The critical Zn concentration in cereal crops below which Zn deficiency is likely to occur varied from 12 to 24 mg/kg. The leaf blade 3 from the top is the most sensitive in relating relative yields of maize shoots to Zn concentration in the tissue. The critical Zn concentration in ten weeks old wheat plants was found to be 17 mg/kg and 24 mg/kg for rice shoot on a dry weight basis. The critical Zn deficiency levels as determined by DTPA extraction varies from soil to soil and from crop to crop