Optimizing Crop Productivity And Fertility Practices In Intermediate Wheatgrass, Roberta Bianchin Rebesquini

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The intensive management associated with many annual crops often includes recurring tillage, fertilization, and pesticide applications, which contribute to environmental concerns such as water pollution and soil erosion. Intermediate wheatgrass (Thinopyrum intermedium), recognized under the trade name Kernza®, is a perennial grass that can be managed to produce grain and biomass while providing desired environmental benefits such as soil conservation and nutrient cycling. There has been limited research on best management practices and crop productivity for this alternative dual-use crop in Nebraska. A field experiment was conducted beginning in 2021 to assess nitrogen (N), phosphorus (P), and potassium (K) management …

Evaluating Drill Interseeded Cover Crop Establishment And Nitrogen Impact In Irrigated Corn, Victor De Sousa Ferreira

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The adoption of cover crops as a strategy to improve soil health and cropping systems sustainability is on the rise in the United States. PRE herbicides with soil residual activity are widely applied in corn production systems to prevent early season weed development, crop-weed competition, and yield loss. When preemergence herbicides are applied in the field, the active ingredients remain in the soil rhizosphere for a period of time, killing weed seedlings as they emerge. However, PRE herbicides can also impact the establishment of interseeded cover crops. Greenhouse bioassay was conducted to evaluate the preemergence herbicide carry-over potential to interseeded …

Plasticity Of Sorghum Biomass And Inflorescence Traits In Response To Nitrogen Application, Kyle M. Linders

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Nitrogen is an essential nutrient required for growth and development in plants. Insufficient nitrogen availability can reduce vegetative growth and grain yield. However, nitrogen is a costly input for farmers, is energy intensive to manufacture, and runoff of excess nitrogen fertilizer impacts water quality. Compared to its close relative, maize, sorghum has much greater resilience to nitrogen and water deficit, and heat stress, allowing sorghum to be grown with fewer inputs and on marginal land. Variation in total biomass accumulation and grain yield between sorghum accessions, as well as between nitrogen conditions, can be largely explained by differences in vegetative …

Nitrification Inhibitor, Nitrogen Source, And Herbicide Effects On Soil Nitrogen Transformations And Corn Yield, William Neels

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Nitrogen fertilizer management continue to be challenging due to potential nitrogen losses under variable weather conditions. The objective of this was to evaluate the performance of nitrification inhibitors, nitrogen sources and herbicides on in-season nitrogen availability and agronomy indicators. A two site-year field experiment was conducted in silty clay loam soil in corn phase of the corn-soybean rotation at Central Nebraska. The treatments included three herbicide (no pre-emergence, Acuron, Resicore) and five nitrogen treatments: 1) control, 2) anhydrous ammonia, 3) anhydrous ammonia without nitrification inhibitor, 4) urea with nitrification inhibitors, and 5) urea without nitrification inhibitors. Results indicated that nitrogen …

Mycorrhizae In Maize (Zea Mays L.) Cropping Systems Respond Differently To Nitrogen Fertilization Under Increasing Crop Rotational Diversity, Morgan Mcpherson

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Arbuscular mycorrhizal fungi (AMF) remain a vital obligate symbiont of nearly all plants. It is well established that the symbiosis between AMF and host plant improves plant nutrient acquisition, alleviates abiotic and biotic environmental stressors, defends against plant pathogens, and contributes to overall plant fitness and productivity through modification of the soil habitat. Modifications include increased soil aggregation and stability, carbon sequestration through provision of fungal wall precursors to soil organic matter (SOM) formation, and enhanced nutrient cycling in the mycorrhizosphere. The goal of this dissertation was to assess how AMF respond to nitrogen (N) fertilization regimes in maize cropping …

Effects Of Different Water And Nitrogen Regimens On Yield Of Winter Wheat Produced In Nebraska, Joseph Emory Davis

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Wheat is the 3rd most prominent crop in the USA and approximately 50% is exported annually. Nebraska wheat production is 11^th in the country, and it plays a major role in the state's agricultural economy, especially in western NE. Generally, wheat is grown under dryland conditions and the region grows much more wheat on unirrigated land than it does on irrigated. However, deficit irrigation has shown great value in producing high yielding wheat with much less water than needed for other crops. Finding new ways to leverage irrigation in wheat production may help address the need to produce food …

Understanding Nitrogen Limitation In Soybean, Nicolas Cafaro La Menza

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Meeting soybean demand on existing cropland area for a global population of 9.7 billion people by the year 2050 requires narrowing the existing gap between average producer yield and yield potential. Soybean relies on two sources on nitrogen (N): biological N2 fixation and indigenous soil N supply. As soybean yield continues to increase, it seems critical to know if there is a yield level at which potential contribution of indigenous nitrogen sources and fixation becomes insufficient to meet crop N requirements for high yields, while still maintaining or increasing protein and oil concentration. This study evaluated N limitation across 29 …

Benchmarking On-Farm Maize Nitrogen Balance In The Western U.S. Corn Belt, Fatima Amor Tenorio

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

A nitrogen (N) balance, calculated as the difference between N inputs and grain-N removal, provides an estimate of the potential N losses. We used N balance with other N-related metrics (partial factor productivity for N inputs, and yield-scaled N balance), to benchmark maize yields in relation with N input use in the US Corn Belt. We first used experimental data on grain-N concentration (GNC) to assess variation in this parameter due to biophysical and management factors. Subsequently, we used N balance and N-related metrics to benchmark yields in relation with N inputs in irrigated and rainfed fields in Nebraska using …

Nitrogen And Water Effects On Canopy Sensor Measurements For Site-Specific Management Of Crops, Nicholas C. Ward

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Water and nitrogen (N) are undoubtedly the two largest agricultural inputs globally. Coupled with advances in site-specific management technology their integration into production agriculture will allow for the most efficient use these crop input resources. Active canopy sensors offer the ability to measure biophysical plant traits rapidly and make assessments about plant status. Specifically, optical sensor measurements of light reflectance assess plant N status allowing for in-season and on-the-go N recommendations and applications; while infrared thermometers (IRT) measurement of canopy temperature can be used a tool for irrigation management. To evaluate how these technologies work among different plant stress environments …

High Yield Soybean Management: Planting Practices, Nutrient Supply, And Growth Modification, Evan Sonderegger

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Growers are constantly seeking ways to improve yield in soybean [Glycine max (L.) Merr.]. There has been much interest in the use of selected alternative practices to maximize soybean yield. These practices include planting soybean at higher than recommended seeding rates, planting soybean in narrow rows, breaking apical dominance to induce branching, application of strobilurin fungicides prophylactically to minimize disease and extend the seed filling period, the use of N fertilizer both in furrow and foliar applied, and the use of seed treatments to promote early stand establishment and health. Field studies were conducted at the University of Nebraska …

A Review Of Cover Crops For Eastern Nebraska, Tyler Williams

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The focus of this project is two fold, first to provide a short literature review of cover crops (CC) and then discuss the results from a field experiment that was designed to evaluate the nitrogen contribution from cover crop mixes to the subsequent corn crop. The literature review will focus on the aspects of CC that are related to the field of study. Cover crops, as defined by the United States Department of Agriculture (USDA) are crops that are agronomically sound and grown for the purpose of erosion control or other objectives related to conservation or soil improvement. Cover crops …

Evaluation Of Algorithm Thresholds For Crop Canopy Sensor-Based In-Season Nitrogen Application In Corn, Brian T. Krienke

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Nitrogen fertilizer is frequently the most limiting nutrient in corn production. Typically most nitrogen is applied before planting. Since nitrogen can leave the soil system fairly easily, the result can be an inefficient use of nitrogen fertilizer. Previous research has shown increased efficiency with no reduction in yield by applying nitrogen later in the season when the crop is actively growing, with rates regulated spatially through the use of active crop canopy sensors. This study evaluated the potential for N cutoff thresholds using a sufficiency index as the threshold value for areas with poor stand or an unrecoverable N deficiency. …

An Integrated Crop- And Soil-Based Strategy For Variable-Rate Nitrogen Management In Corn, Darrin F. Roberts

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Nitrogen (N) management in cereal crops has been the subject of considerable research and debate for several decades. Historic N management practices have contributed to low nitrogen use efficiency (NUE). Low NUE can be caused by such things as poor synchronization between soil N supply and crop demand, uniform application rates of fertilizer N to spatially variable landscapes, and failure to account for temporally variable influences on soil N supply and crop N need. Active canopy reflectance sensors and management zones (MZ) have been studied separately as possible plant- and soil-based N management tools to increase NUE. Recently, some have …