determinants of soil and wheat zinc concentrations: an on ... · determinants of soil and wheat...
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Determinants of soil and wheat zinc concentrations: an on-farm study in Madhya Pradesh, India
Master thesis Julian Helfenstein Supervised by Prof. Emmanuel Frossard, ETH Dr. Gurbir Bhullar, FiBL Department of Environmental Systems Science (D-USYS), ETH Zürich July 2015
On-farm study of zinc in organic and conventional wheat cropping systems
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Abstract Zinc plant nutrition is of key relevance in India, as a large fraction of the population suffers from zinc malnutrition and many soils are naturally low in extractable zinc. To date, there is no known on-farm study comparing zinc grain density in organic and conventional wheat production in India. In this on-farm study in Madhya Pradesh we analyzed soil and wheat grains on 30 organic and 30 conventional farms, focusing on soil extractable zinc, wheat grain yield, and wheat grain zinc concentration. Results show that soil total and extractable zinc concentrations are similar in organic and conventional cropping systems, but organic wheat accumulated more zinc in the grains (p = 0.03). In addition to higher zinc concentrations, organic wheat grains also contained more nitrogen (p = 0.058) and sulfur (p = 0.046), suggesting higher protein density, despite attaining the same yield level as conventional (p = 0.94). Multiple linear regression revealed that soil total zinc and total sulfur concentrations best predicted soil extractable zinc (adjusted R2 = 0.25); available phosphorus, exchangeable potassium, and silt content best predicted yield (adjusted R2 = 0.24); and yield, available phosphorus and the cropping system best predicted the grain zinc concentration (adjusted R2 = 0.33). Overall, it appears that organic grains contained more zinc due to combined effects of lower available phosphorus levels in the soil, higher grain protein concentration, and in some cases lower yield. The study thus underlines the potential of well-managed organic wheat cropping to increase food security in Madhya Pradesh by producing competitive yields with improved zinc and protein concentrations.