Wednesday, November 15, 2006 - 1:55 PM

How Zinc Soil Chemistry Affects Health of People Who Eat Rice.

Sarah Johnson1, Jack D.C. Jacob1, Roland J. Buresh1, Julie Lauren2, and John M. Duxbury3. (1) IRRI, DAPO Box 7777, Metro Manilla, Philippines, (2) Tower Rd., Cornell University, Cornell University, 917 Bradfield Hall, Ithaca, NY 14853, (3) Cornell Univ, Tower Road, 917 Bradfield Hall, Ithaca, NY 14853

Zinc (Zn) deficiency is a human health concern in many parts of rice-producing Asia. Inadequate dietary intake of Zn can lead to decreased immune system function, leaving vulnerable populations more susceptible to infectious illnesses such as diarrhea and respiratory infections. In areas where people get a majority of their calories from rice consumption, increasing the amount of Zn in rice grains would contribute to mitigation of Zn deficiency-related diseases. Zinc deficiency has commonly been an agronomic problem in flooded rice production due to soil chemical changes with decreasing redox potential, which limits the availability of soil Zn for plant uptake.  Even when the agronomic Zn-deficiency problems have been overcome through Zn fertilization, differences remain in plant uptake of Zn based upon crop management practices such as irrigation and residue incorporation. In a field experiment, incorporation of maize or rice residue into a flooded rice paddy resulted in a decrease in Zn uptake by rice plants in spite of soil application of 10 kg Zn ha-1.  In a pot experiment, treatments that raised the soil redox potential by altering water management increased Zn uptake into rice plants, even when all treatments included soil application of 14 kg Zn ha-1.  Understanding the effects of crop management on Zn uptake will enable assessment of the effects of agronomic recommendations on human nutrition, and will aid plant breeding programs in their efforts to enrich food crops with micronutrients in varied environments.