Brief Summary of Minutes of Annual Meeting

Accomplishments by major objectives of the Project:

1. Gain a more thorough understanding of the influence of macro- and micro-scale ecosystems and landscape properties on soil N dynamics.

Soil health tests are important for determining impacts and evaluation of management practices on soil N dynamics. Activities have focused on evaluating various tests of soil health and effects of cover crops and nitrogen-efficiency-enhancing products on soil nitrogen availability.

Short-term Outcomes:

(A) Two components of the Haney soil health nutrient tool (HSHT) accounted for the most variation in economic optimum N rate (EONR). Both accounted for >50% of variation in EONR for N applied. With additional research, these two components may help improve N recommendations for corn in the Midwest in comparison with the soil health score.

(B) Similar to other soil measurements, mineralizable C had multiple sources of variability: spatial, temporal and analytical. This underscores the need for the development of a standardized and universally adopted protocol. The sources of variability were soil-specific and may be a substantial hurdle to its utility as a robust soil health metric.

Outputs:

Products in 2018 include: seven state reports (CA, IA, KY, MN, MS, NE, TN); 23 grants; 15 peer-reviewed publications; and 18 presentations at professional meetings and meetings for commodity groups, producers and stakeholders Please see attachments for details. Students trained included 14 graduate and 8 undergraduates.

Activities:

(A) Evaluated the Haney soil health nutrient tool (HSHT) for its potential in determining corn nitrogen recommendations, using research results from a study conducted at multiple sites across eight Midwest states. (B) Examined numerous sources of laboratory variability associated with mineralizable C, with the overall goal of understanding the influence of each source variability to determine whether this test is robust enough for adoption by the soil test industry. The analysis included soil from eight studies on 72 agricultural cropland sites from across the United States, using permutations of soil processing and rewetting protocols (n = 1142 individual observations) to determine the sources of variation associated with these procedures. (C) Numerous other studies, e.g., use of cover crops and use of spatial statistics for optimizing N fertilizer use.

2. Explore optimization of nitrogen management practices through interrogation of corn nitrogen use efficiency datasets from studies conducted across the North Central region.

Soil N tests are key to optimizing yields, while also preventing over application of fertilizer N. Some field sites, for example, show no yield response to fertilizer N addition but still have high yields. A test that predicts when a site will respond to N fertilizer, but has high yields, is crucial to understanding what factors contribute to these high-yielding sites and how N application can be reduced based on that knowledge.

Short-term Outcomes:

A combination of two soil N tests, 14-d aerobic incubation and tetraphenyl borate extraction, best predicted AONR.

Outputs:

The combination of the two above tests shows potential for reducing and optimizing N fertilizer rates, which would reduce the cost of N fertilizer for farmers and reduce reactive N pollution.

Activities:

A large data set with 56 site-years of N response trials from the North Central region (dataset from NC1195 committee) was analyzed for N response and factors that may predict response.

3. Develop nitrogen management decision-making tools for crop advisers and growers.

Activities are focused on 1) improving the ability to forecast N rate requirements in Iowa and 2) engaging the general public, growers, and crop advisers in learning about N cycling in Iowa agricultural systems and N reduction strategies.

Short-term Outcomes:

The Corn Nitrogen Rate Calculator web site (http://cnrc.agron.iastate.edu/) had 103,084 page views and 12,523 unique visitors in 2018. Since its inception in May 2018, the website for Nitrogen Model for Iowa Agricultural Systems (https://www.nrem.iastate.edu/nmodel/) has received nearly 150 unique visitors. This website is also used in teaching about the N cycle for students in Introductory Ecology at Iowa State.

Outputs:

Products include one journal article and one is in review. The online Corn Nitrogen Rate Calculator N response database was updated with new research data for corn following soybean and continuous corn. One new website is available to the public.

Activities:

1) Corn yield results from a long-term N rate by rotation research site near Ames were used to investigate the potential for the Agricultural Production Systems sIMulator (APSIM) model to improve or supplement current N rate recommendations.

2) A website was created that provides access to and instructions for a user-friendly, process-based simulation model for the general public. The topic: N cycling in Iowa agricultural systems.

Milestones:

1) Complete research on soil N testing and N response across diverse soils, the residual effects of long-term N application on soil N supply and crop yield response in corn cropping systems, and N rate and tillage effect on corn yield by September 2020.

2) Submit publications by March 2020.

3) Disseminate the research outcomes to peers, producers and other stakeholders in 2019-2020.