Zinc deficiency in vertisols of India and Australia

• Indian Council of Agricultural Research, India
• CSIRO Division of Soils, Australia

Large area of Vertisols, which are important cropping soils in subtropical India, Africa and Australia, are deficient in zinc. Correction of deficiencies by addition of zinc is expensive, and therefore requirements need to be predicted accurately. Predictions based on current soil tests are unreliable, because there is little accurate information on the factors that influence zinc uptake. There is also concern, particularly in India, that the effects of zinc applied to Vertisols are short-lived, leading to low recovery of applied zinc by crops.
The central activity of the project will involve field trials on Vertisols in Madhya Pradesh, India and in southern Queensland, Australia. Responses of wheat grown in winter and sorghum in summer to applications of zinc will be measured. Wheat and sorghum are important dryland crops in both areas.
The effects of zinc application will be examined in a number of ways. Scientists in Australia will undertake a detailed physico-chemical characterisation of the soils employed, and will assess the changes over time in the chemical status of applied zinc in the soils. This work should enable scientists to identify the soil properties that most critically affect zinc availability to plants and to devise effective methods for routine measurement.
Vesicular-arbuscular mycorrhizae (VAM) are microorganisms capable of significantly increasing zinc uptake by crops growing in Vertisols. The scientists in Toowoomba Australia and in Jabalpur, India, will examine the mechanism whereby VAM aids zinc absorption (including the ability to absorb insoluble zinc reaction products), and will characterise the sites of field experiments according to their VAM status.
Trials at the Queensland Wheat Research Institute will elucidate the interactions of other factors on the uptake of zinc. These factors include species differences in sensitivity to zinc supply and the influence of drying of the fertilised soil layer on zinc deficiency and plant response.
Comprehensive models for predicting zinc requirements will be developed from the trials, which will relate responses of crops treated with zinc fertiliser, measured in the field experiments, to soil, plant and environmental factors.
Results of the project will be communicated to the All-India Coordinated Programme on Micronutrients and to Indian farmers through state government agencies and the Fertiliser Association of India. There is a potential spillover benefit for farmers on the Vertisols of Africa, and farmers in Australia will also benefit through the State government agricultural extension networks.