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Iowa State University

Plant Sciences

Graduate Theses and Dissertations

Cover crops

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Investigating The Interactions Between Cover Crops And The Soybean Cyst Nematode Through Lab, Greenhouse, And Field Studies, Chelsea Jean Harbach Jan 2019

Investigating The Interactions Between Cover Crops And The Soybean Cyst Nematode Through Lab, Greenhouse, And Field Studies, Chelsea Jean Harbach

Graduate Theses and Dissertations

Throughout the past decade, the acres on which cover crops have been planted in agricultural systems in the United States has increased. In traditional row cropping, cover crops are sown shortly before or after the harvest of corn or soybean and grown through the fall to provide ground cover for approximately one third of the year during which the soil would otherwise be bare. Cover crops have many known environmental benefits, but the effects they may have on soybean cyst nematode (SCN), Heterodera glycines, are not well established. This dissertation describes experiments conducted i) in the laboratory and greenhouse to ...


Cover Crop Effects On Maize Productivity: Insights From Statistical And Process-Based Models, Guillermo Marcillo Jan 2018

Cover Crop Effects On Maize Productivity: Insights From Statistical And Process-Based Models, Guillermo Marcillo

Graduate Theses and Dissertations

Winter cover crops can be an effective strategy to buffer soil and water impairing effects from intensively managed agriculture. While cover crops have shown potential to sequester off-season nitrate, control weeds, or promote nutrient cycling, knowledge gaps persist in regard to maize impacts driven by cover crop decision making. In this context, statistical and process-based models can be valuable tools for predicting changes in maize systems that include a winter cover crop. In a meta-analysis combining peer-reviewed research from several regions in the US, grain yields were found to change between 0 and 21% when maize (Zea mays L.) followed ...


Evaluating The Impacts Of Midwestern Cropping Systems On Soil Health And Subsurface Drainage Water Quality, Brian Dougherty Jan 2018

Evaluating The Impacts Of Midwestern Cropping Systems On Soil Health And Subsurface Drainage Water Quality, Brian Dougherty

Graduate Theses and Dissertations

Agricultural nutrient management practices are an important component of the effort to improve water quality in the Mississippi River Basin. In particular, there is concern about nutrient export to the Gulf of Mexico via loss from subsurface drainage systems. Optimizing the use of fertilizers and animal manures in combination with other management practices has the potential to minimize negative impacts on water quality. Farmers are increasingly challenged to maximize crop production while utilizing fertilizers and animal manures in an efficient and environmentally friendly manner. An increasing awareness of the potential to address these issues by improving soil health has also ...


Drivers Of Yield And Nitrogen-Loss Tradeoffs: Cropping System Evaluations With Process-Based Modeling, Rafael Alejandro Martinez-Feria Jan 2018

Drivers Of Yield And Nitrogen-Loss Tradeoffs: Cropping System Evaluations With Process-Based Modeling, Rafael Alejandro Martinez-Feria

Graduate Theses and Dissertations

The Midwest is one of the most productive agricultural regions, but mitigating loss of nitrogen (N) from cropland is needed to improve environmental quality. Tradeoffs between crop yield and N loss have been linked largely to the inefficient use of N fertilizers, but the contributions of more systemic factors such as soil characteristics, crop sequences, and genotypes have not been thoroughly studied. This dissertation examines and quantifies the impact of various genetic, environmental and management drivers of crop yield and N-loss tradeoffs in the maize and soybean cropping systems of the US Midwest, and identifies potential management strategies to lessen ...


Integration Of Summer And Fall Cover Crops In Vegetable Cropping Systems, Raymond Albert Kruse Jan 2015

Integration Of Summer And Fall Cover Crops In Vegetable Cropping Systems, Raymond Albert Kruse

Graduate Theses and Dissertations

The demand for locally produced vegetables is growing in the Midwest, including Iowa. However, since vegetables are a small fraction of total cropland in the state, little research exists on approaches and techniques to increase the sustainability of vegetable production systems. Including cover crops in vegetable crop rotations can contribute to sustainability in vegetable cropping systems. This research investigated the integration of summer and fall cover crops in vegetable cropping systems to reduce weeds and nutrient leaching, improve soil chemical and biological properties, and enhance crop growth, yield, and produce quality. Cover crops studied in this research included buckwheat (Fagopyrum ...


Suitability Of Winter Canola (Brassica Napus) For Enhancing Summer Annual Crop Rotations In Iowa, Rafael A. Martinez-Feria Jan 2015

Suitability Of Winter Canola (Brassica Napus) For Enhancing Summer Annual Crop Rotations In Iowa, Rafael A. Martinez-Feria

Graduate Theses and Dissertations

Winter canola (Brassica napus) could be a good candidate for enhancing cropping systems in Iowa because of its potential to provide environmental benefits and produce a marketable crop compatible with existing grain production and distribution schemes. However, it is still uncertain whether this crop would be suitable for helping balance environmental and financial goals of conventional cropping systems under the environmental and market conditions unique to Iowa. The work presented in this thesis is an effort to assess the suitability of winter canola for providing environmental benefits while fitting within the logistic and economic constrains of current cropping systems. Based ...


Evaluation Of Cover Crops In Reduced Tillage Systems For Organic Production, Dan Edward Cwach Jan 2012

Evaluation Of Cover Crops In Reduced Tillage Systems For Organic Production, Dan Edward Cwach

Graduate Theses and Dissertations

Negative environmental impacts associated with intensive pesticide use and over-fertilization in conventional production have encouraged many producers to investigate organic methods. In the most current (2008) U.S. Department of Agriculture (USDA) statistics on organic agriculture, land under certified organic production increased to 4.8 million acres, with 194,637 acres of organic corn (Zea mays L.), 125,621 acres of organic soybean [Glycine max (L.) Merr.], and 164,888 acres in organic vegetable crops. In order to enter the expanding organic market and meet certified organic requirements, producers must implement a soil-building plan that focuses on preserving soil organic ...


Alternative Weed Management Practices: Effects On Weed Control, Grapevine Performance, And Soil Quality In An Established Midwestern Vineyard, Lisa Marie Wasko Jan 2010

Alternative Weed Management Practices: Effects On Weed Control, Grapevine Performance, And Soil Quality In An Established Midwestern Vineyard, Lisa Marie Wasko

Graduate Theses and Dissertations

Sustainable grape production entails the implementation of management practices that control weeds, maintain grapevine performance, and conserve soil quality. Conventional weed management practices include herbicide application and/or cultivation. These practices compromise soil quality by limiting additions of organic matter and exposing the soil surface, thereby leaving it prone to degradative processes. With the expansion of continental climate viticulture in areas with rain-fed agriculture, such as in the Midwest, there is a need for sustainable weed management practices that optimize production while conserving soil quality. The primary objective of this investigation was to evaluate weed management practices in an established ...