Project : USDA ARS

ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Research Project #431860

Research Project: Increasing the Productivity and Resilience to Climate Variability of Agricultural Production Systems in the Upper Midwest U.S. while Reducing Negative Impact on the Environment

Location: Soil and Water Management Research

2019 Annual Report

Objectives
1. Assess the environmental impacts of crop management practices that have the potential to improve soil health and decrease greenhouse gas emissions in the Upper Midwest. a. Develop a perennialized row crop system that reduces the environmental footprint of agriculture and improves its resilience, without adverse impacts on water usage and profitability. b. Develop new knowledge regarding soil nitrogen cycling and nitric and nitrous oxide production mechanisms. c. Develop new knowledge of chemical triggering compounds of microbial activity. 2. Increase nutrient use efficiency and reduce nutrient losses to leaching, runoff and atmospheric emissions in Upper Midwest cropping systems. a. Develop improved methods to quantify and to reduce losses of reactive N gases from fertilized cropping systems. b. Evaluate manure management practices for improvement of nutrient cycling and reduction of reactive nitrogen losses on large dairies.

Approach
All the objectives of this project have a common focus on quantifying the impacts of management practices, including crop rotation/cover crops, irrigation, and synthetic N fertilizer or manure amendments, on GHG emissions and nutrient availability for crop uptake or susceptibility to loss to the environment. The different objectives complement each other in several ways. In order to gain insights from multiple perspectives, the methods for each objective range across scales, including large field and larger plot studies (sub-objective 1a); replicated small-plots (2a); soil column mesocosms (2b); and laboratory microcosms (1b, 1c). The same set of soil types representing a range of Minnesota agricultural soils from across the state, including soil from both field experiments (1a and 2a), will be used in the microcosm and mesocosm experiments (1b, 1c and 2b). Thus, results from the three laboratory experiments each of which have different primary objectives, will inform and help to interpret results of the other lab studies; and results from the lab experiments under more controlled conditions will inform results of the field experiments that are subject to dynamic climate conditions. Both of the field experiments (1a and 2a) will measure greenhouse gas emissions and ammonia volatilization losses from cropping systems under similar soil types (the same soil series) but with different management regimes, which may also allow for cross-site comparison of results. This research also complements efforts within several national projects and initiatives, including the Greenhouse Gas Reduction through Agricultural Carbon Enhancement (GRACEnet), Resilient Economic Agricultural Practices (REAP), Dairy Agro-ecosystem Working Group (DAWG) and Long-Term Agricultural Research (LTAR) networks; and as such will involve collaboration with several colleagues from other ARS locations, universities and other organizations.

Progress Report
Sub-objective 1a. Develop a perennialized row crop system that reduces the environmental footprint of agriculture and improves its resilience, without adverse impacts on water usage and profitability. The second year of a two-year field experiment designed to determine the nitrogen (N) requirements for corn grown in a kura clover living mulch (KLCM) was completed and the data were analyzed and submitted for publication. Results showed that first-year corn following two-three years of forage management did not require fertilizer N to maximize yield and profitability, while second-year corn required a fertilizer N rate near local university guidelines for corn following soybean. An economic analysis was also completed which showed that net return from corn grain and stover in the KCLM system averaged over both growing seasons was $138 per ha greater than a conventional corn comparison. Sub-objective 1b. Develop new knowledge regarding soil nitrogen cycling and nitric and nitrous oxide production mechanisms. Incubation experiments using three soil types in triplicate, each at five temperatures, with and without addition of a nitrification inhibitor analyzed for seven response variables (NH+4, NH3, NO2-, NO3-, NO, N2O and pH) on 11 sampling dates resulted in a large data set (> 900 data points) that required extensive analysis. Two separate publications are being prepared to report the complete results of this experiment; one manuscript describes a process-based model of nitrification and associated gas production and compares model simulations to a subset of the data in the absence of nitrification inhibitor; and one manuscript applies the model to data with nitrification inhibitor. The first manuscript is well-developed and should be submitted before end of the fiscal year. Sub-objective 1c. Develop new knowledge of chemical triggering compounds of microbial activity. Due to the government shutdown, a series of soil incubation experiments that were underway prior to the shutdown had to be terminated. This resulted in 3-4 months of extra effort, due to the loss of analytical data that could not be collected during the furlough. The experiments were restarted and data are being collected and analyzed statistically as they are generated. The goal is to be back on schedule with milestones by next year. Sub-objective 2a. Develop improved methods to quantify and to reduce losses of reactive N gases from fertilized cropping systems. The field experiment was expanded using extramural funds obtained from Eurochem Agro and in collaboration with University of Minnesota – St. Paul researchers. The first year of the two-year field study was successfully completed at three field sites including an experiment with corn in St. Paul, Minnesota, and two experiments in Becker, Minnesota one with corn and one with potato. Each experiment was continued for a second year and is progressing as planned, with measurements of nitrous oxide emissions, nitrate leaching, soil nitrogen, plant tissue nutrient content and crop yields. Each experiment is comparing seven replicated treatments, including (i) a no-fertilizer control, (ii) urea only, (iii) urea plus the nitrification inhibitor DMPSA, (iv) urea plus the urease inhibitor NBPT, (v) urea plus DMPSA and NBPT, (vi) urea plus a microbial inoculant, and (vii) urea plus DMPSA and the microbial inoculant. A laboratory incubation experiment was also completed comparing a subset of these treatments. The automated flux chamber system for semi-continuous measurement of greenhouse gas fluxes is still undergoing repairs and testing. Sub-objective 2b. Evaluate manure management practices for improvement of nutrient cycling and reduction of reactive nitrogen losses on large dairies. A manuscript on the column leaching experiment to evaluate losses of nitrogen (N) and phosphorus (P) from manure and non-manure sources on a range of soils was drafted. Additional field experiments, in collaboration with an ARS researcher in Madison, Wisconsin, and a University of Minnesota – St. Paul researcher, were conducted through a second winter. The experiments are designed to determine P and N release from a snowpack with application of dairy manure under, within, or atop the snowpack. The experiments will provide data for model development and extend earlier laboratory work that described nutrient release to water over expected range of temperatures in Minnesota.

Accomplishments
1. Rotary zone tillage improves the performance of corn in perennial living mulch systems. Perennial living mulches are farming systems that provide the environmental benefits of cover crops in row crop agriculture, including reductions of erosion and chemical runoff, without the need to replant each year. One plant that is commonly used as a living mulch is kura clover, a long-lived legume that spreads by rhizomes. Strip tillage can be used to establish rows in it for planting corn or soybeans, but yields are often reduced compared to conventional production. We hypothesized that one reason for yield reduction might be early season competition for light, water, and nutrients, and that this could be ameliorated by creating a wider tilled zone. To test this hypothesis, we employed a novel rotary zone tillage unit (RZT) that uses rotary tines to create a wide (30 cm) cleared zone for each row. This system was compared against a traditional shank-based strip tillage unit (ST) for corn production over two growing seasons. We measured early season temperature and water content within the rows, biomass production of both corn and kura clover, and corn yield in both systems. In both years, corn emerged earlier and developed faster in the RZT plots. There was no significant difference in yield in the first season between the systems, but in the second season there was a substantial benefit to the rotary zone tillage system, which produced 4.0 Mg ha-1 in grain and 3.5 Mg ha-1 more stover, with no significant impact of kura clover biomass production. We conclude that the RZT system improves the likelihood for successful corn production in perennial living mulch systems, which should improve the adoption rate of this promising new farming system.

2. Biostimulant additives for co-application with urea result in unintended nitrogen losses. Urea is the dominant form of nitrogen (N) fertilizer in much of the USA and globally. Various additives have been designed for co-application with urea to improve performance of N-intensive crops including potato. Few if any studies have compared microbial ‘inhibitor’ additives with so-called ‘biostimulants’ designed to enhance plant growth or microbial activity. Over two potato growing seasons in an irrigated potato system in Minnesota, we found that a biostimulant containing N-fixing microbes (NFM) increased nitrous oxide (N2O) gas emissions by more than 30%, in contrast to the inhibitors, which decreased N2O emissions by more than 40%. Also, in the wetter of the two growing seasons, NFM also increased NO3- leaching by 23%. Biostimulants can have unintended impacts on reactive N losses and should be used with caution pending additional study to better understand their effects on biological processes and to quantify their performance in other agro-ecosystems. These results will assist producers and policy makers in developing practices for improving nutrient use efficiency and reducing nitrogen losses to the environment.

3. A perennial living mulch reduces fertilizer N requirements and increases profitability of corn. Kura clover living mulch (KCLM) systems have been investigated for their incorporation into upper Midwestern row crop rotations to provide ecosystem services through continuous living cover, but factors affecting agronomic performance and nutrient management are not well defined. Field experiments conducted in 2017 and 2018 showed that first-year corn following two-three years of forage management did not require fertilizer N to maximize yield and profitability, while second-year corn required a fertilizer N rate near local university guidelines for corn following soybean. The net economic return from corn grain and stover in the KCLM system averaged over both growing seasons was $138 per ha greater than a conventional corn comparison. The KCLM cropping system provides a new economically viable option for corn growers.

U.S. DEPARTMENT OF AGRICULTURE

Soil and Water Management Research: St. Paul, MN