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  • Author or Editor: Sharon J.B. Knewtson x
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A survey was conducted of 81 growers managing 185 high tunnels in Missouri, Kansas, Nebraska, and Iowa to collect information about their high tunnel management practices. The survey was administered from 2005 to 2007 using internet-based and written forms. The average respondent had 4 years of high tunnel experience. The oldest tunnel still in use was 15 years old. Twenty-five percent of respondents grew crops in their high tunnels year-round. Tomato (Solanum lycopersicum), lettuce (Lactuca sativa), spinach (Spinacia oleracea), cucumber (Cucumis sativus), pepper (Capsicum spp.), leafy greens, and flowers were the most common crops. Organic soil amendments were used exclusively by 35% of growers, and in combination with conventional fertilizers by an additional 50% of growers. The summary of management practices is of interest to growers and the industries and university research and extension scientists who serve them. Growers typically reported satisfaction with their high tunnels. Growers with more than one high tunnel had often added tunnels following the success of crop production in an initial tunnel. Labor for crop maintenance was the main limiting factor reported by growers as preventing expanded high tunnel production.

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Microbial tea from a commercial source and a homemade manure tea were evaluated for 2 years under organic and conventional fertility regimens. Testing with different fertility regimens allowed broader assessment of tea efficacy. Collard green (Brassica oleracea L. var. acephala cv. Top Bunch) yield and soil microbial activity were measured after microbial tea applications were made in three fertility treatments (conventional, organic, or no fertilizer amendment) on a previously unfertilized sandy loam soil. Spinach (Spinacia oleracea L. cv. Hellcat) and collard green yields were determined after commercial microbial tea application to a silt loam soil previously managed with organic or conventional vegetable crops in open fields and under high tunnels. Results indicated that nutrient additions influenced crop yields, even doubling yield. This demonstrated that improved nutrient availability would affect yield at the chosen locations. However, microbial tea applications did not affect crop yield. These results did not support the hypothesis that microbial tea improves plant nutrient uptake. Additionally, soil microbial respiration and biomass were unaffected after two or three tea applications.

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Growers have indicated that changes in soil quality under production in high tunnels is an important problem, but these have not yet been quantified or critically assessed in the central Great Plains of the United States. We conducted surveys of grower perceptions of soil quality in their tunnels (n = 81) and compared selected soil quality indicators (salinity and particulate organic matter carbon) under high tunnels of varying ages with those of adjacent fields at sites in Kansas, Missouri, Nebraska, and Iowa in the United States. Fourteen percent of growers surveyed considered soil quality to be a problem in their high tunnels, and there were significant correlations between grower perceptions of soil quality problems and reported observations of clod formation and surface crusting and to a lesser extent surface mineral deposition. Grower perception of soil quality and grower observation of soil characteristics were not related to high tunnel age. Soil surface salinity was elevated in some high tunnels compared with adjacent fields but was not related to time under the high tunnel. In the soil upper 5 cm, salinity in fields did not exceed 2 dS·m−1 and was less than 2 dS·m−1 under 74% of high tunnels and less than 4 dS·m−1 in 97% of high tunnels. The particulate organic matter carbon fraction was higher in high tunnels than adjacent fields at 73% of locations sampled. Particulate organic matter carbon measured 0.11 to 0.67 g particulate organic matter per g of the total carbon under high tunnels sampled. Particulate organic matter carbon in the soil was also not correlated to age of high tunnel. Soil quality as measured in this study was not negatively impacted by use of high tunnel structures over time.

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The sustainability of soil quality under high tunnels will influence management of high tunnels currently in use and grower decisions regarding design and management of new high tunnels to be constructed. Soil quality was quantified using measures of soil pH, salinity, total carbon, and particulate organic matter (POM) carbon in a silt loam soil that had been in vegetable production under high tunnels at the research station in Olathe, KS, for eight years. Soil under high tunnels was compared with that in adjacent fields in both a conventional and an organic management system. The eight-year presence of high tunnels under the conventional management system resulted in increased soil pH and salinity but did not affect soil carbon. In the organic management system, high tunnels did not affect soil pH, increased soil salinity, and influenced soil carbon (C) pools with an increase in POM carbon. The increases in soil salinity were not enough to be detrimental to crops. These results indicate that soil quality was not adversely affected by eight years under stationary high tunnels managed with conventionally or organically produced vegetable crops.

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