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Mathieu Ngouajio and Milton E. McGiffen Jr.

Organic agriculture is growing in importance worldwide. In the United States, the rate of increase of organic growers was estimated at 12% in 2000. However, many producers are reluctant to undertake the organic transition because of uncertainty of how organic production will affect weed population dynamics and management. The organic transition has a profound impact on the agroecosystem. Changes in soil physical and chemical properties during the transition often impact indirectly insect, disease, and weed dynamics. Greater weed species richness is usually found in organic farms but total weed density and biomass are often smaller under the organic system compared with the conventional system. The improved weed suppression of organic agriculture is probably the result of combined effects of several factors including weed seed predation by soil microorganisms, seedling predation by phytophagus insects, and the physical and allelopathic effects of cover crops.

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Hongjian Wei, Wen Yang, Yongqi Wang, Jie Ding, Liangfa Ge, Michael Richardson, Tianzeng Liu, and Juming Zhang

and 2020). The correlation among physiological responses, soil properties, leaf morphology, mechanical strength, cell wall component, and wear tolerance was calculated by Spearman’s test at two significance levels, P < 0.05 and P < 0.01. Linear or

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Nancy G. Creamer, Mark A. Bennett, Benjamin R. Stinner, and John Cardina

Four tomato production systems were compared at Columbus and Fremont, Ohio: 1) a conventional system; 2) an integrated system [a fall-planted cover-crop mixture of hairy vetch (Vicia villosa Roth.), rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and barley (Hordeum vulgare L.) killed before tomato planting and left as mulch, and reduced chemical inputs]; 3) an organic system (with cover-crop mixture and no synthetic chemical inputs); and (4) a no-input system (with cover-crop mixture and no additional management or inputs). Nitrogen in the cover-crop mixture above-ground biomass was 220 kg·ha-1 in Columbus and 360 kg·ha-1 in Fremont. Mulch systems (with cover-crop mixture on the bed surface) had higher soil moisture levels and reduced soil maximum temperatures relative to the conventional system. Overall, the cover-crop mulch suppressed weeds as well as herbicide plots, and no additional weed control was needed during the season. There were no differences in the frequency of scouted insect pests or diseases among the treatments. The number of tomato fruit and flower clusters for the conventional system was higher early in the season. In Fremont, the plants in the conventional system had accumulated more dry matter 5 weeks after transplanting. Yield of red fruit was similar for all systems at Columbus, but the conventional system yielded higher than the other three systems in Fremont. In Columbus, there were no differences in economic return above variable costs among systems. In Fremont, the conventional systems had the highest return above variable costs.

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Kirandeep K. Mann, Arnold W. Schumann, Thomas A. Obreza, and Jerry B. Sartain

The soils under Florida citrus production have very poor natural fertility. Furthermore, on some sandy soils, the problems of spatial variability in yield and soil properties are very common. The poor growth areas of a field have a much lighter soil

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Huisen Zhu and Deying Li

where the major water sources contain high salt levels also experience salinity problems. Salts cause physiological stress on turfgrasses ( Slavens et al., 2009 ) and have negative effects on soil properties including structure, water movement, and

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Shawna Loper, Amy L. Shober, Christine Wiese, Geoffrey C. Denny, Craig D. Stanley, and Edward F. Gilman

plot) in each block. Half of each plot was planted with ornamental plants and the other half was planted with turfgrass (subplot) as described previously. The soil treatments were assigned randomly within each block. Soil properties were analyzed using

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Kuan Qin and Daniel I. Leskovar

on watermelon yield, quality, WUE, and soil property changes under a deficit irrigation schedule. WUE can be measured at the crop level (yield-to-water use ratio), plant level (biomass-to-water loss ratio), and leaf level (CO 2 assimilation

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Ashley A. Thompson and Gregory M. Peck

, compost increased soil properties that are associated with long-term soil fertility, such as OM, soil C, and microbial respiration. It is possible that these increases will positively impact orchard productivity in future years. Increased soil mineral

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Amit Bhasin, Joan Davenport, Scott Lukas, Qianwen Lu, Gwen Hoheisel, and Lisa W. DeVetter

growth, yield, fruit quality, floral bud set, cold hardiness, tissue macronutrient concentrations, and select soil properties. It was hypothesized that postharvest N fertilizer applications would result in increased yields by promoting plant growth from

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Alba A. Clivati McIntyre, David M. Francis, Timothy K. Hartz, and Christopher Gunter

18% to 27% ( Sacks and Francis, 2001 ). The majority of the variability was the result of unknown causes or interactions between variables (25% to 50%). We postulated that location differences are closely tied to soil properties and soil fertility