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Iowa State University

2018

Plant Sciences

Graduate Theses and Dissertations

Cover crops

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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 ...