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  • Author or Editor: Carl J. Rosen x
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Consumer demand for organically grown produce has increased dramatically over the past decade, most likely because of the perceived benefits to the environment and human health. A major component of organic production is providing organic sources of nutrients to promote plant growth as well as sustain soil quality. Organic nutrition of plants can present opportunities and challenges to the grower. The primary objective of this article is to review scientifically based information dealing with the effects of organic nutrient sources on crop yields and quality, soil properties, and environmental risks. Effects of organic nutrient sources are often evaluated by comparison with conventional production, but this approach can be problematic because nutrient source may be confounded with many other cropping system components. Despite these drawbacks, a careful examination of the literature suggests the following conclusions. Soil quality is generally improved with application of organic nutrient sources, but careful management is required to avoid environmental risks of nitrate (NO3) leaching and phosphorus accumulation. Provided that nutrient supply is equal, yields with organic sources tend to be similar to those with inorganic sources. However, lack of available nitrogen (N) that is synchronous with plant demand often limits yields in organic cropping systems. Limited N availability and varied supply of other nutrients from organic sources may contribute to the differences sometimes observed in dry matter content, tissue NO3 and mineral concentration, vitamin C and other phytochemicals, and taste. Phytonutrient content also may be affected by differences in pest control strategies among cropping systems regardless of nutrient source. There is a slight, but significantly, increased risk of produce contamination by Escherichia coli and other enteric bacteria contamination on produce when organic nutrient sources are used, but if proper guidelines are followed, contamination with the lethal serotype O157:H7 does not appear to be a major concern. Appropriate management of organic inputs is critical to achieving potential benefits for crop production and soil quality.

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Five primocane raspberry (Rubus idaeus) cultivars were evaluated in a high tunnel and in the field at Grand Rapids, MN, which is located in U.S. Department of Agriculture (USDA) plant hardiness zone 3b. Bare root plants of five cultivars (Autumn Bliss, Autumn Britten, Caroline, Joan J, and Polana) were planted in the high tunnel and in the field, each with a randomized complete block design at 2 × 5.2-ft spacing on 8 May and 14 May 2008, respectively. A propane heater was used periodically for frost protection in the high tunnel. All five cultivars overwintered well and primocanes emerged with minor or no winter damage in the high tunnel in 2009. The high tunnel extended the growing season for ≈4 weeks in both years. Raspberry plants in the high tunnel produced higher yield than those in the field, total 154 lb (6655 lb/acre) from the high tunnel vs. 0.5 lb (43 lb/acre) from the field in 2008 and 379 lb (16,378 lb/acre) vs. 80 lb (3457 lb/acre) in 2009. ‘Caroline’ and ‘Polana’ had higher yields than ‘Autumn Bliss’; ‘Joan J’ and ‘Autumn Britten’ yields were intermediate and not different from ‘Caroline’, ‘Polana’, or ‘Autumn Bliss’ yields. In terms of harvest date, ‘Polana’ was the earliest among the five cultivars tested, followed by ‘Autumn Britten’, ‘Autumn Bliss’, and ‘Joan J’. ‘Caroline’ was the latest. Essential nutrients in leaves for all cultivars both in the field and in the high tunnel were within sufficient ranges. Spider mites (Tetranychidae) and raspberry sawflies (Monophanoides geniculatus) were the major insect problems. In conclusion, primocane-fruiting raspberries can be successfully grown in high tunnels and produce substantially higher yields than in field plantations in northern Minnesota or areas with similar climatic conditions.

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Composting of municipal solid waste (MSW) has received renewed attention as a result of increasing waste disposal costs and the environmental concerns associated with using landfills. Sixteen MSW composting facilities are currently operating in the United States, with many more in the advanced stages of planning. A targeted end use of the compost is for horticultural crop production. At the present time, quality standards for MSW composts are lacking and need to be established. Elevated heavy metal concentrations in MSW compost have been reported; however, through proper sorting and recycling prior to composting, contamination by heavy metals can be reduced. Guidelines for safe metal concentrations and fecal pathogens in compost, based on sewage sludge research, are presented. The compost has been shown to be useful in horticultural crop production by improving soil physical properties, such as lowering bulk density and increasing water-holding capacity. The compost can supply essential nutrients to a limited extent; however, supplemental fertilizer, particularly N, is usually required. The compost has been used successfully as a sphagnum peat substitute for container media and as a seedbed for turf production. High soluble salts and B, often leading to phytotoxicity, are problems associated with the use of MSW compost. The primary limiting factor for the general use of MSW compost in horticultural crop production at present is the lack of consistent, high-quality compost.

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