Field-Validation of Critical Limits for Applying Noncomposted Bovine Manure to North Central Region Vegetable Production Soils

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This project builds on completed research, using soil beds in controlled environment chambers, that resulted in preliminary recommendations for the safe application of non-composted bovine manure to soils. </p>
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In general, these recommendations were to apply non-composted bovine manure in late winter/early spring while soil still undergoes freeze/thaw cycling and to also follow the USDA National Organic Program standard of at least 120 days between manure application and harvest of vegetables whose edible portion contacts the soil surface or soil particles.</p>
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We also recommended against summer application of non-composted bovine manure prior to planting and harvest of fall harvested vegetables. However, reported shortcomings of model systems studies, as well as our preliminary field studies, clearly point to the need for field-validation of our preliminary recommendaitons before extending them to North Central region vegetable farmers.
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Field-validation studies will be conducted at University of Wisconsin-Madison Agricultural Research Stations in Lancaster, West Madison, and Hancock. The soils at these stations represent a wide range of soil types and histories in the North Central Region. </p>
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At each station, a research plot will be divided into 44 sectors, with each sector randomly assigned a combination of manure spreading date, tilling date, and addition/absence of additional straw spread with the manure. Manure (no more than 1 day old) will be applied at a rate of 67.2 metric tons (wet weight) per hectare. in the sectors, representative leaf and root crops will be planted for spring harvest (e.g. radish and lettuce planted in spring) or fall harvest (e.g. carrot planted in spring, lettuce planted in late summer). </p>
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Crops will be watered by rainfall, and irrigation if necessary, with amounts recorded. Vegetables will be sampled for numbers/presence of Escherichia coli at thinning and harvest. Soils will be anayized for numbers/presence of E. ccli at biweekly intervals. </p>
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Previous research has shown that indigenous (generally non-pathogenic) E. coli is a suitable surrogate for pathogenic E. coil and Salmonella that may occasionaly be present in noncomposted bovine manure. In addition, soil samples will be analyzed for numbers of protozoa and nematodes.</p>
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We will test the hypothesis that addition of straw to land-spread bovine manure will enhance protozoan and nematode predation of E. coil and lead to more rapid decreases in E. coil numbers. </p>
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The overall experiment will be carried out over two growing seasons and three winters. At the end of each growing season manure will be applied to control sectors and the effect of winter conditions on E. coli survival will be evaluated. </p>
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Results of soil analysis will be statistically analyzed to determine which treatment combinaiton leads to the most rapid decrease in numbers of E. coli. Results of vegetable analyses will also be analyzed and the collective results will be used to develop recommendations for North Central region vegetable farmers wishing to use noncomposted bovine manure as fertilizer.
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Bovine manure is a readily available fertilizer in the North Central region, but use of non-composted bovine manure in vegetable production may result in contamination of vegetables with disease-causing intestinal bacteria such as Salmonella and certain types of Escherichia coli. This project will field-validate recommendations on when and how non-composted bovine manure can be safely applied in the North Central region to prevent contamination of vegetables. </P>
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PROGRESS: 2002/01 TO 2002/12 <br>
During the fall, 2002, field plots were set up at the West Madison, Hancock, and Lancaster Agricultural Research Stations. At each site, non-composted bovine manure was applied to two randomly selected plots. In an additional two randomly selected plots at each station, a mixture of non-composted manure and chopped straw was applied. The manure or manure/straw was incorporated in the soil using a shovel, Initial sampling and analysis for indigenous Escherichia ccli was conducted for each plot and additional samples were taken and analyzed approximately one month after manure application. Additional samples will be analyzed for each plot when sampling is again possible in the spring. Decreases in E. coli numbers of approximately two orders of magnitude occurred between manure application and follow-up sampling, indicating the lethality of freeze/thaw cycling to E. coli in the manure-fertilized soil system. </p>
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IMPACT: 2002/01 TO 2002/12 <br>
It is expected that results of this project will provide North Central vegetable growers with reliable guidelines for application of non-composted bovine manure such that contamination of vegetables with feces-borne pathogenic bacteria does not occur. </p>