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Cover Crops and Nitrogen Retention
Cover crops are an integral component of cropping systems because they grow in the fall and early spring - that is, times when the soil would not have a growing corn or soybean crop. At present, cover crops are grown to benefit soil quality and reduce nitrate loss. In the future, ongoing research at ISU promises to identify additional benefits such as weed suppression. Cover crop acres are growing exponentially. The Iowa Nutrient Reduction Strategy highlights cover crops as a flagship strategy for nitrate loss reduction. We are working to understand how cover crops can be inserted to corn-based crop systems to maximize cash crop yield, soil quality and nutrient loss reduction.
Nitrogen Use Efficiency
Soil organic matter increases crop yield amount and stability. Soil organic matter - not nitrogen fertilizer - is the largest source of crop nitrogen uptake and environmental nitrogen loss. For example, approximately 10% of Iowa corn acres are non-responsive to nitrogen fertilizer in any given year despite yields that exceed regional averages- however, predicting those acres is extremely challenging.
To increase nitrogen retention and nitrogen use efficiency, we must improve our understanding of the processes that control inorganic nitrogen fertilizer transformation to soil organic matter, and subsequent re-transformation of soil organic matter back to crop-available inorganic nitrogen (a process known as 'mineralization').
Biophysical Factors Affecting Nitrous Oxide Fluxes
Soil is the largest terrestrial source of nitrous oxide. In agricultural cropping systems, nitrous oxide typically represents the largest net greenhouse gas flux. Increases in farm efficiency are well known to reduce nitrous oxide emissions. We take advantage of cropping systems experiments to advance our basic understanding of biophysical controls on nitrous oxide flux while improving agroecosystem models and management strategies. Much of our current work is funded by USDA NIFA as part of a regional greenhouse gas monitoring network that we coordinate: www.sustainablecorn.org
Forecast and Assessment of Cropping sysTemS (FACTS; 2015-present)
FACTS is an ongoing project developed to forecast and evaluate real-time soil-crop dynamics in specific ISU fields. Predictions and measurements will be frequently updated as new information becomes available during the growing season.
What we do:
- During the growing season we provide real-time measurements and forecasts for weather, soil water and nitrogen, crop water and nitrogen, yield predictions, crop stage and heat/frost stress.
- Before/after the growing season we benchmark production, economic, and environmental performance, estimate the yield gaps, and perform what-if scenario analysis to identify management practices with the highest profits and lowest environmental impacts.
Why we do it:
- To provide quantitative answers to questions that farmers commonly ask such as what is going to be the yield this year, how much nitrogen is in the soil today, do I have enough soil water for the next few days, what if I had used more nitrogen, planted more seeds, gotten more rain.
- To improve the science behind predictive tools, ground-truth predictions, and explore different approaches to accurately forecasting yields.
Low-cost nitrate sensors to populate genotype-informed yield prediction models for next generation breeders
Our civilization depends on continuously increasing levels of agricultural productivity, which itself depends on (among other things) the interplay of crop varieties and the environments in which these varieties are grown. Hence, to increase agricultural productivity and yield stability, it is necessary to develop improved crop varieties that deliver ever more yield, even under the variable weather conditions induced by global climate change, all the while minimizing the use of inputs such as fertilizers that are limiting, expensive or have undesirable ecological impacts. By coupling a network of innovative, low-cost nitrate sensors across multiple environments within the heart of the corn belt and advanced cropping systems modeling (APSIM, the most widely used modeling platform), the proposed research will enhance our understanding of and ability to predict yield and Genotype x Environment interactions. The integration of nitrate (N) dynamics into this model is expected to greatly increase the accuracy of its predictions. Because we will also integrate genotypes into this model, the proposed research outlines a new and innovative approach for breeding crops that exhibit increased yields and yield stability. It will be possible to readily translate this approach to other crops. By generating data on nitrate concentrations in soil and in planta at unprecedented spatial and temporal resolution at multiple sites with different soil characteristics and weather, the proposed research will also improve our understanding of N cycles in both the soil and plant. Although essential to plant growth and high yields, when over-applied N can result in a variety of serious negative externalities, some of which are currently the subject of high-impact litigation in Iowa. Project outcomes have the potential to provide guidance to farmers about how to apply sufficient but not excessive amounts of N fertilizer, resulting in both economic benefits to farmers and positive environmental externalities.Our focus on creating a new approach to breeding for yield stability meets the USDA sustainability goals to "satisfy human food and fiber needs" and "sustain the economic viability of farm operations". Our focus on nitrogen meets the USDA sustainability goals to "enhance environmental quality" and to "make the most efficient use of nonrenewable resources...and integrate, where appropriate, natural biological cycles and controls". More specifically, this proposal addresses the NIFA-Commodity Board co-funded priority for "development and application of tools to predict phenotype from genotype" and the "the development of high-throughput phenotyping equipment and methods".
Improving cereal rye cover crop BMPs to increase adoption of cover crops by Iowa farmers (2018-2020)
Issue: The Iowa Nutrient Reduction Strategy (INRS) calls for cover crop implementation on over 12 million acres, which equates to every other field. Despite numerous environmental benefits associated with cover crops, many farmers are still hesitant to change their current production practices. Major barriers to introducing cover crops as a conservation practice include cost of implementation, yield drag, and knowledge. This multi-disciplinary team will address the barriers of using cover crops and develop best management practices (BMPs) for including a cover crop in a corn-soybean production system in Iowa for “hesitant” farmers. Using these data, we will develop a set of BMPs with a partial cost budget to encourage farmers to include cover crops in corn-soybean production systems, and therefore meet the INRS goals of cover crop acreage adoption in Iowa.
Objective: This research will evaluate the effect of cover crop seeding rate, seeding method, and termination timing on corn production, soil health and nutrient recycling. Treatment effects on (i) cover crop and corn growth and development (ii) weed, pest and disease pressure, (iii) nutrient recycling and (iv) soil health will be assessed. In addition, partial budgets for treatments will be developed, and Iowa farmers surveyed to identify common methods of seeding cover crops users and perceived efficacy of those methods.
Approach: A comprehensive field study at the ISU Ag Engineering and Agronomy Farm, with smaller studies at the ISU Southeast Research Farm, Crawfordville, and Northwest Research Farm, Sutherland will be done. Experimental treatments will consist of a three seeding rates, two planting methods (drilled and broadcast) seeding rates, and rye termination timing. Cover crops will be seeded after soybean. The following data will be collected: cover crop growth and development in the fall and spring; corn growth and development throughout the growing season; weed, insect and disease pressure; soil and plant nitrate, soil health parameters. Relationships between data variables will be evaluated to improve our understanding of factors influencing the winter rye-corn cropping systems.