Effect of Cover and Green Manure Crops on Soil Health, Plant Health and Tuber Yield in Organic Sweet Potato Production

Graduate Student Final Report – Ceres Trust Research Grant

Graduate Student: Waana Kaluwasha, Department of Plant Sciences, University of Missouri- Columbia
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Faculty Advisor: Dr. Xi Xiong, Department of Plant Sciences, University of Missouri-Columbia
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Project Period: 2016 – 2017


Interest in organic sweet potato production in the United States has been growing as consumers and producers are becoming increasingly concerned about how their food is cultivated. Thus, there is a growing need for information on sweet potato production under an organic production system. Organic sweet potato growers are challenged by sustainable soil management, which impacts the occurrence of soilborne disease, weeds, and other pest issues that consequently reduce the tuber yield. Being organic, their options are limited for pest control, especially fungal disease that affects the roots and/or tubers reducing their marketable quality. The research aimed to develop a strategy of using cover and/or green manure crops, and to evaluate their effects on soil and plant health, as well as disease and weed suppression. The experiment was conducted at a Certified Organic Producer’s field based in central Missouri. Effects of rapeseed and cereal rye, incorporated as cover or green manure crops, were assessed in a randomized complete block design for a one-year period. Soil samples were collected for soil organic matter, pH, nutrients, and microbial analysis by using phospholipid fatty acid (PLFA) analysis three times over the course of the study. The PLFA assessed various groups of fungi and bacteria for their diversity and density. Evaluations also included weed coverage, sweet potato plant vigor, disease occurrence (Fusarium root rot), and sweet potato yield. Results from this experiment would increase our knowledge on how to best incorporate cover crops into organic sweet potato production by improving soil health as well as suppressing weed and disease.

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