Effects of Conventional and Organic Agricultural Systems on the Root Health of Maize
Weinhold, Melissa C.
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Many plant pathogens attack a plant through its root system. A healthy root system is less susceptible to disease and so is vital to the health of the plant. This investigation focused on the health of the roots of the corn (Zea mays L.) plant under different conditions. We compared corn populations from four families that had been bred under farming conditions that employed conventional applications of mineral fertilizers with four populations that were derived from them but which were selected under organic farming conditions (only organic manures). The former populations were bred by the USDA and Iowa State University, the latter by Michael Fields Agricultural Institute (MFAI). In 1996, all these corn populations were grown in soil which had been in a grass alfalfa sod for three years. To test whether the breeding history affected the growth of roots and their health, we grew the populations on subplots with either mineral fertilization or sheep manure compost. Health of roots was determined from counts of total roots and discolored roots using the line-intersect method of Tennant (1975). The highest number of healthy roots were produced by the organically bred com growing under organic fertilization. The Iowa populations had a greater percentage of discolored roots than populations from MFAI and the BSSS family was the most prolific in overall production of roots. These results are consistent with the hypothesis that root systems grown under organic conditions are healthier than root systems grown in conventional conditions.