Browsing by Subject "Cover crops"
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Item Assessing Biodiversity in Summer Cover Crop Rotations for Beneficial Arthropod Conservation(2022-05) Candelaria-Morales, NaomyIntensive vegetable crop practices can have detrimental effects on soil health, draining soil of organic matter reserves and necessitating nitrogen (N) inputs. These amendments can support crop productivity but may have considerable environmental consequences including overfertilization, water eutrophication, and reduce fauna (Agostini et al., 2010). In addition, many vegetable crop rotations are characterized by high plant density but low beneficial arthropod and pollinator habitat diversity (Carreck and Williams, 2001). Habitat simplification may cause declines in beneficial arthropods, which can lead to insufficient pollination services and increased pest pressure (Hogg et al., 2011; Wilson et al., 2018). Out of numerous arthropod services, pollination, pest control, dung burial and wildlife nutrition have been estimated to value at least $57 billion USD (Forister et al., 2019). Because of sheer amount of agricultural land, comprising over 40% of all U.S. land, agricultural ecosystems present valuable opportunity in maintaining biodiversity (USDA, 2012). Constant forage availability from early spring to late summer is particularly imperative for the survival of social insects with long-lived colonies, such as bees (Carreck and Williams, 2001). The use of cover crops can expand the seasonal availability of floral resources in agroecosystems (Hooks et al. 1998; Landis et al. 2005). In a two-part study, this research investigated the effects of summer-planted cover crops on soil nutrient contributions and beneficial arthropod density, diversity, richness and evenness. Part one consisted of a one-year (2019) field trial study where nine treatments, each containing one to seven species of cover crops, were evaluated for flowering, aboveground biomass production and nitrogen (N) content, soil-N contribution after biomass incorporation, and beneficial arthropod visitation. A seven-species mix composed of oat (Avena sativa L.), field pea (Pisum sativum subsp. Arvense L.) and 5 clover species (Trifolium spp.) added the largest amount of biomass (8747 kg/ha). Likewise, this mix contributed the most organic N (265.6 kg N/ha) and maximum soil -N subsequently increased after biomass incorporation (10.9 mg -N/kg of soil). Part two consisted of a two-year (2020-2021) study evaluating the ability of two rotational systems of summer cover crop species, selected from 2019 trials, to provide key multifunctional ecosystem benefits to vegetable crop production. The first system was an early cover crop planting followed by a broccoli cash crop, and the second system consisted of an early planting of spring lettuce followed by a late summer cover crop planting. In all three years, buckwheat (Fagopyrum esculentum Moench) and phacelia (Phacelia tanacetifolia Bendth.) monoculture produced most abundant floral resources. Beneficial arthropods observed included pollinators (native, honey and bumblebees), predators (syrphid flies and minute pirate bugs), and parasitoids. Increased floral diversity was associated with abundance of flies in the family Syrphidae. Phacelia monoculture was most attractive for bees in the families Apidae and Halictidae, both of which may provide pollination services. These results highlight floral visitation patterns as an indicator for beneficial arthropod community support and conservation. Summer-planted cover crops are an underexplored rotation option for organic farming systems in the Upper Midwest and may support a wide range of ecosystem services including increases in available soil N and beneficial arthropod services.Item Factors affecting the successful establishment of an overseeded winter rye cover crop in northern climates(2012-07) Wilson, Melissa LoraineIncorporating cover crops in the corn-soybean rotation is one way to improve soil quality over time and reduce nitrogen and erosion losses. In the Upper Midwest, however, cover crops can be difficult to establish after harvest of the main crop due to the short growing season. Overseeding prior to harvest may allow more time for growth. Three experiments were conducted to determine what factors are most likely to affect successful establishment of overseeded winter rye into standing corn and soybeans. The first experiment field tested aerial seeding at multiple locations in southeastern Minnesota to characterize the physical and chemical properties that affect fall biomass production. Precipitation within a week of seeding was found to be the most important factor in establishing a successful cover crop. The second experiment further elaborated on this by testing soil water potential and temperature on germination of rye seeds under laboratory conditions. Total germination was significantly decreased by decreasing water potential in the sandy loam, but not the clay or silt loam, suggesting that moisture content may be more important than water potential at the soil surface. Increasing temperature decreased total germination, most likely due to the increased incidence of mold at higher temperatures. The third experiment evaluated three overseeding techniques for standing soybeans: aerial seeding (AS), tractor-mounted air-flow spreader (TAF), and tractor-mounted fertilizer broadcast spreader (TBS). The AS treatment resulted in the lowest seeding density overall while the TBS treatment resulted in the highest density and was the most variable across plots. The differences in seeding density led to significant above-ground rye biomass differences in fall, although by spring, biomass was not different across seeding treatments. Soybean yields were not different across seeding techniques, suggesting that any of these practices are viable for on-farm use. Finally, the potential for overseeding cover crops, aerial seeding in particular, as a practice in the Upper Midwest was evaluated. Some of the current limitations include unpredictable weather, lack of aerial applicators, inconsistent stands due to pilot error and seed predation, and high costs.Item Implications of adopting soil health practices on the economic performance of Minnesota row crop operations(2021-02) Wilts Johnson, KatherineProduction agriculture has a large dependency on Earth’s resources, resulting in a strong endorsement of reduced tillage and cover cropping systems on row crop farms from conservationists and soil health specialists. Despite this endorsement, there are low adoption rates of these conservation practices which directly affect agriculture production and profitability. Part one of this study uses an ordinary least squares model to determine the impact of conservation and conventional tillage systems on yield for Minnesota corn, soybean, and spring wheat farms. Part two of this study uses the yield estimates from part one to estimate the impact of cover crop adoption on field-level profitability, considering cover crops as both a single-year and multi-year decision. Results indicate that many cover crop scenarios do not show positive cash flows unless used with cost-share assistance. Results also indicate that the profitable cover crop scenarios incorporate the lowest cost options of cover crop seed, planting, and termination methods.Item Integrated weed management in soybean(2013-10) Flipp, Amanda MarieStudies were conducted in 2011 and 2012 at two sites at the Southern Research and Outreach Center in Waseca, MN to evaluate different combinations of row spacing, soybean varieties, and early season weed control treatments on giant ragweed, common lambsquarters, and tall waterhemp density, biomass, and seed production. The early season weed control treatments consisted of a pre-emergence herbicide, winter rye cover, and radish/pennycress cover mixture. Overall, a flumioxazin, acetochlor, or winter rye treatment were the most effective in reducing weed density, biomass, and seed production. These two treatments generally resulted in at least a 50% reduction in total weed density compared to the control. A flumioxazin or winter rye treatment resulted in no weed seed production of common lambsquarters at Site 1 in 2011, compared to 2018 seeds m-2 in the control. Results demonstrate the importance of early season weed control as part of a comprehensive weed management plan. Soybean row spacing and variety were not as effective in reducing weed density, biomass, and seed production. However, they were important as part of an integrated weed management strategy when used in combination with the winter rye cover crop and flumioxazin or acetochlor in controlling weeds in soybeans. A fully integrated approach is needed to control weeds, either to prevent herbicide resistant weeds or to manage herbicide resistant weeds.Item Methods and knowledge towards the improvement of legume cover crops for the Northern U.S.(2021-01) Wiering, NicholasCorn and soybean production currently occupy 67% of all Minnesota cropland. Cover cropping, though up more than 40% since 2012, only occupies 2.7% of MN cropland. Logistically, the short growing season in northern states hinders establishment and return on investment for cover crops compared to environments with longer growing seasons. Nonetheless, summer-annual production without winter vegetative cover leaves soil barren for most of the year, making it vulnerable to soil erosion via water or wind. Projections of rainfall intensification in the Upper Midwest may worsen the situation, where ~10 t per hectare of soil are already lost in the Lake States each year. Without vegetative cover from late autumn to early spring, un-sequestered nitrates are easily lost to ground water or waterways, which is accelerated by the 37% of MN cropland above tile drainage. Cover crops provide one method to reduce these negative externalities of crop production on MN landscapes. However, the immediate challenge is incorporating them into an already established cropping system, without reducing the productivity or profitability of that system. Legume cover crops, if able to survive harsh winters, could provide an economic incentive to farmers due to biological N fixation, which could also reduce global reliance on synthetic-N, which is the most energy-expensive input for convention farmers. However, very little effort has been made to improve legume cover crops for Northern U.S. cropping systems. To improve the performance and adaptability of legume cover crops, foundational research will be required that provides knowledge of traits of interest (Chapter 2), methods to select desirable phenotypes (Chapter 3), and resources to facilitate variety improvement (Chapter 4). Though the challenges of cover crop improvement and implementation are much the same for legume species, this thesis primarily focuses on improvement efforts for the winter-hardy annual legume, hairy vetch (Vicia villosa R.).Item Wet Meadow Revegetation Following Invasive Plant Control(Minnesota Department of Transportation, 2008-01) Iannone III, Basil V.; Galatowitsch, Susan M.Phalaris arundinacea invades sedge meadow restorations, forming persistent monotypes that prevent community establishment. Eradicating Phalaris, however, leaves restored ecosystems prone to reinvasion. In order to restore desired plant communities, methods to control Phalaris are needed. To determine if reducing light by sowing cover crops and reducing nitrogen by incorporating soil-sawdust amendments would prevent Phalaris invasions, a study was conducted under conditions similar to a restored wetland in two experimental basins with controlled hydrology. Seeds of a 10-species target community and Phalaris were sown in plots with high diversity, low diversity, or no cover crops in soils with or without sawdust amendments. Nitrogen, light, tissue C:N ratios, firstyear seedling emergence, establishment, and growth, and second-year above ground biomass were measured. Only high diversity cover crops reduced light and sawdust reduced nitrogen for about 9 weeks. Similar trends in firstyear seedling data and second-year biomass data suggested Phalaris control efforts should focus on establishing perennial communities rather than implementing separate resource-limiting strategies. Sowing high diversity cover crops resulted in Phalaris-dominated communities, making cover crops an ineffective Phalaris control strategy. Using sawdust amendments did not reduce Phalaris invasion much beyond what the target community did but resulted in a community similar to those of natural sedge meadows by increasing the abundance of seeded species from the Cyperaceae family and colonization of non-seeded wetland species. The target community apparently reduced Phalaris invasion by reducing both light and nitrogen. Regardless, no treatment fully prevented invasion, making follow-up Phalaris control necessary to ensure community recovery.