Organic Wheat Farming Improves Grain Zinc Concentration

PLoS One. 2016 Aug 18;11(8):e0160729. doi: 10.1371/journal.pone.0160729. eCollection 2016.

Abstract

Zinc (Zn) nutrition is of key relevance in India, as a large fraction of the population suffers from Zn malnutrition and many soils contain little plant available Zn. In this study we compared organic and conventional wheat cropping systems with respect to DTPA (diethylene triamine pentaacetic acid)-extractable Zn as a proxy for plant available Zn, yield, and grain Zn concentration. We analyzed soil and wheat grain samples from 30 organic and 30 conventional farms in Madhya Pradesh (central India), and conducted farmer interviews to elucidate sociological and management variables. Total and DTPA-extractable soil Zn concentrations and grain yield (3400 kg ha-1) did not differ between the two farming systems, but with 32 and 28 mg kg-1 respectively, grain Zn concentrations were higher on organic than conventional farms (t = -2.2, p = 0.03). Furthermore, multiple linear regression analyses revealed that (a) total soil zinc and sulfur concentrations were the best predictors of DTPA-extractable soil Zn, (b) Olsen phosphate taken as a proxy for available soil phosphorus, exchangeable soil potassium, harvest date, training of farmers in nutrient management, and soil silt content were the best predictors of yield, and (c) yield, Olsen phosphate, grain nitrogen, farmyard manure availability, and the type of cropping system were the best predictors of grain Zn concentration. Results suggested that organic wheat contained more Zn despite same yield level due to higher nutrient efficiency. Higher nutrient efficiency was also seen in organic wheat for P, N and S. The study thus suggests that appropriate farm management can lead to competitive yield and improved Zn concentration in wheat grains on organic farms.

MeSH terms

  • Edible Grain / chemistry*
  • Edible Grain / growth & development
  • Organic Agriculture / methods*
  • Soil / chemistry
  • Triticum / chemistry*
  • Triticum / growth & development
  • Zinc / analysis*

Substances

  • Soil
  • Zinc

Grants and funding

The project was funded by WFSC Mercator Research Program (http://www.worldfoodsystem.ethz.ch/research.html) and was conducted in the framework of long-term farming systems comparison in the tropics (SysCom) program, which is financially supported by Biovision Foundation for Ecological Development, Coop Sustainability Fund, Liechtenstein Development Service (LED) and the Swiss Agency for Development and Cooperation (SDC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.