Location: Forage Seed and Cereal Research Unit
2017 Annual Report
Objectives
This research will identify crop rotation practices used in Pacific Northwest (PNW) grass seed production systems over the past decade and quantify the benefits of crop rotation diversity in promoting long stand life and high probability of successful establishment of new stands. It will also determine the value of biochar from syngas production in improving soil chemistry and quality. These data will be used to analyze farm management options that promote sustainable and profitable farming complying with environmental regulations, making wise-use of natural and crop production resources. This work will address the cumulative effects of crop management practices, field application of char, and both current and proposed conservation programs at the landscape scale, and as part of Conservation Effects Assessment Project (CEAP), determine whether the specific combinations of practices, placement, and timing will achieve desired environmental goals. These studies will be conducted in a region of highly diverse cropping systems, complex hydrology and landuse patterns, and numerous mandates to meet natural resource quality standards, including the Clean Water and Endangered Species Acts.
Objective 1. Quantify the impact of specific management practices in forage seed and cereal production systems that impact productivity and profitability.
Sub-objective 1.1. Assess the impact of diverse crop rotations on reducing input costs and breaking weed and disease cycles associated with crop diversity that increase crop and soil productivity.
Sub-objective 1.2. Quantify the impact of on-farm energy produced from crop residues and utilization of the biochar co-product as a soil amendment on energy-related input costs, soil quality, and soil carbon and nitrogen dynamics.
Sub-objective 1.3. Identify microbial products and populations that enhance agricultural productivity by improving soil health.
Objective 2. Utilize quantitative data produced in Objective 1 to develop alternative sets of management practices that optimize farm profitability and sustainability.
Sub-objective 2.1. Utilize field data to calibrate SWAT and other complex modeling tools and quantify multiple environmental effects of on-farm energy production, stand duration, tillage and nitrogen use in management of seed and cereal crops.
Sub-objective 2.2. Evaluate the effects of differing mixtures of forage seed and cereal management practices on farm-scale profitability across a diverse landscape and identify optimal sets of practices appropriate in contrasting production environments.
Approach
Meeting societal expectations for stable supplies of food and fiber while maintaining natural resource quality requires knowledge of trade-offs among multiple, often competing, objectives. Profitability along with long-term sustainability and ecosystem trade-offs are impacted by production decisions, regulations, policy, and purchasing preferences. This research project will develop information on crop management practices that promote long-duration seed crop stand life and successful establishment of new stands, the potential of char produced by gasification of crop residues as a soil amendment and value-added farm product, and will culminate in optimization analyses utilizing these data so producers and policy-makers can be given sets of management options that achieve productivity, sustainability, and profitability in different ecosystems and under alternative climate change scenarios to help bring about economic sustainability at the farm level and ecosystem services at the landscape level. The information and technologies developed within these Pacific Northwest (PNW) agroecosystems are integral parts of Conservation Effects Assessment Project (CEAP), Renewable Energy Assessment Project (REAP) and GRACEnet (Greenhouse Gas Reduction through Agricultural Carbon Enhancement network). This approach will be applied to analyze biofuel production in the Upper Mississippi River and Columbia River Basins, contrasting agroecosystems.
Progress Report
Grass seed growers in Western Oregon use crop rotations to control pests, revitalize soil, and decrease weeds. Understanding the identity and the duration of the rotation, which bridges the cessation of one grass seed stand and the establishment of the next grass seed crop, can shed light on the roles that weeds or pests play in decisions to grow specific crops or to conduct quick or prolonged rotations out of grass seed production. Object-based classification techniques were used to identify eleven years of crop rotation sequences in western Oregon, in support of Subobjective 1.1. The significance of these crop rotations, the durations of stand grown prior to or following the rotation period, and general soil properties were evaluated using spatial statistics. The analysis showed that management operations within individual fields were more important in determining crop rotations than other factors, including soil properties or gradations in precipitation or temperature. By identifying the most commonly used crop rotations, hypotheses regarding the impact of specific management practices on the build-up or dissipation of pests during transitions from one grass seed crop to the next, can be proposed and evaluated.
Rotational crops are an important management tool that have the potential to control weeds, improve soil health, and prevent plant disease. However, resources that evaluate or communicate the efficacy of rotational crops in meeting management goals are lacking. The goal is to develop crop rotation indexes that can help growers make management decisions. The development of crop rotational diversity indexes progressed. Object-based classification techniques revealed that crop rotation sequences differed in several ways, including the duration of the rotation, the identity of the crops (including fallow), and fall versus spring plantings of grass seed stands. The strength of the relationship between these factors and key indicators of the economic viability of grass seed production were calculated to determine if a specific rotational crop could help meet management goals. The first component of a crop rotation diversity index, the number of rotational years spanning grass seed crops, was calculated. Analyses of other factors, including management regimes, are ongoing and will contribute to the development of the indexes.
Biochar, a carbon-rich by-product of energy production, has received growing attention as a soil amendment that can improve soil structure, increase crop production, and sequester carbon. However, little is known about how biochar interacts with soil to influence soil moisture dynamics. In support of Sub-objective 1.2, we evaluated the potential for gasified wood and grass biochars to improve soil water retention in a range of agricultural soils throughout Oregon and Washington. Laboratory measures of moisture release showed increases in plant-available water at amendment rates as low as 1% by mass in most soils. Using a model of field hydrological balance (the Soil Plant Air Water model), the potential benefits of biochar amendment under dryland and irrigated field conditions were estimated from laboratory measurements. Under both current and projected climate conditions, biochar provided modest benefits for soil water conservation when applied at economically-feasible rates. In combination with other cultural practices, gasified biochars can provide benefits for drought adaptation.
Despite the agronomic benefits of biochar, few farmers have adopted biochar-based strategies that improve soil health and increase plant productivity. Lack of supply, cost, and application challenges have led to this disconnect between proof-of-function and adoption. Furthermore, intrinsic variability between biochar products has impeded the use of biochars in agricultural settings and has slowed the emergence of agronomic recommendations. To address some of the barriers that limit adoption of biochar-based amendments, web-based tools that help users learn about char, select chars that are appropriate for their soil needs and farm priorities, and locate biochar producers and suppliers were developed. Collectively, these tools transfer knowledge from researchers and early adopters to the general public. Additionally, these tools connect users to regional biochar resources in support of sub-objective 1.2. These tools are available to the public through a collaboration with Oregon State University at www.PNWBiocharAtlas.org.
Greenhouse experiments determined that coamending mine tailings with a mixture of biochar and lime, may help drive phytostabilization of the 76-acre Formosa Mine Superfund site, in support of Sub-objective 2.2. At many mine sites, the microbial-mineral interactions spawn a biogeochemical cycle that perpetuates and increases soil acidity, which generally impedes the establishment of plant communities. If the fundamental goal is to establish a permanent ground cover, it will ultimately be important to shift the microbial community structure to break this biogeochemical cycle. Reports have indicated that biochar applications impact microbial communities. Still, little is known about the dynamics of microbial communities in assisted phytostablization efforts, or if modulating these populations can accelerate plant establishment and/or stabilize favorable soil conditions. The purpose of these studies was to assess the microbial community at Formosa and determine the impact of adding biochar directly to mine soils, with and without lime addition. The microbial community was assessed using soil enzyme and droplet digital polymerase chain reaction (PCR) assays. In general, we observed significant increases in beneficial microbial populations. The results demonstrate that biochar can influence microbial communities in mine remediation efforts and may help propel the establishment of plant communities.
In perennial grass seed crops, the economic loss due to weeds is substantial and the indirect cost of weed management is even more considerable. Therefore, novel herbicides are needed to control annual seed germination in perennial crops, including Tall Fescue and Perennial Ryegrass. Progress within Sub-objective 1.3 significantly advanced our understanding of the evolution and distribution of the genes that underpin the production 4-formylaminooxyvinylglycine (FVG), a germination arrest factor (GAF) that specifically inhibits the germination of weedy grasses. Biosynthetic enzymes, regulatory factors and transporters essential for FVG production and accumulation are encoded by the GAF vinylglycine (gvg) gene cluster. In order to understand more about the diversity and general underpinnings of FVG production, the evolution of the gvg gene cluster was examined by sequencing the genome of several FVG-producing bacteria and by mining databases of microbe genomes. Over 30 bacterial strains with FVG-associated gene clusters, including Pseudomonas fluorescens, P. syringae and several non-pseudomonas bacteria were identified. The distribution and genetic context of the gvg cluster among bacterial species suggested that it had been inserted multiple times in different bacterial lineages. The fate of gvg clusters post insertion reveals examples of gene loss and gene decay but little rearrangement. Outside of Pseudomonas, further diversification is apparent through insertion of other genes perhaps leading to niche adaption. The frequency in which the cluster appears in unrelated strains suggests a useful function for FVG for diverse bacteria living in a variety of environmental habitats.
The novel herbicide FVG also acts as an antibiotic towards the plant pathogen Erwinia amylovora, the causal agent of fire blight in orchard crops. Although application of FVG may control E. amylovora, resistance to FVG emerges quickly under laboratory conditions. Understanding the mechanisms that underpin FVG resistance could increase the efficacy of anti-Erwinia activity, and lend insight into antibiotic resistance mechanisms, in support of Sub-objective 1.3. In collaboration with scientists in Regina, Saskatchewan, the mechanism of FVG-resistance was determined by analyzing genome variants of spontaneous E. amylovora mutants. Our research indicated that antibiotic resistance was due to null mutations in the L-asparagine permease, a protein normally involved in the import of amino acids. Artificial expression of the L-asparagine permease gene, ansP, in normally resistant Escherichia coli under laboratory conditions was sufficient to impart FVG susceptibility. This suggests that FVG is imported through this permease and that resistance to FVG is imparted by preventing its import. We also determined that mutations in ansP do not confer resistance to aminoethoxyvinylglycine (AVG), a compound that is structurally similar to FVG. Because resistance to AVG and FVG are conferred by different mutations, a mixture of oxyvinylglycines may be a more reliable option for controlling E. amylovora in orchard crops.
The Soil Water Assessment Tool (SWAT) was used to predict regional environmental and agronomic impacts under different climate models, in support of sub-objective 2.2. Crop yields and soil erosion were modeled using SWAT by imputing downscaled daily weather predictions from 10 separate climate models for 2010 to 2099. Average temperature differences between the last (2090-2099) and first (2010-2019) decades of the models ranged from +2.6 to +5.7 °C, with average annual precipitation differences from -78 to +219 millimeters. The model predicted that changes in precipitation and temperature would contribute to an increase in soil erosion from 2 megatonnes/ hectare (MT/ha) under current conditions to 38 MT/ha for the most extreme case. The model also predicted that yields from winter wheat, grass seeds, and legumes may decrease up to 50% by 2090-2099.
Accomplishments
1. Agronomic models predict the impact of climate variability on crop yields and soil erosion. Crop yields and soil erosion were modeled with the Soil and Water Assessment Tool (SWAT) by ARS researchers in Corvallis, Oregon. Daily weather from 10 separate climate model ensembles were used to model scenarios from 2010 to 2099. Increases in temperature and precipitation influenced soil erosion, which increased from a modeled value of 2 MT/ha under current conditions to 38 metric tons per hectare (MT/ha) for the most extreme case. Changes in temperature and precipitation also influenced crop yields. The highest yields of winter wheat and grass and legume seed crops occurred in 2010-2019 model runs, with reductions exceeding 50% by the year 2099. This research with models like SWAT are valuable for predicting agroecosystem response to changes in climate.
2. Decision-support tools provide a regional resource for biochar users and producers. Despite the agronomic benefits of biochar, few farmers have adopted biochar-based strategies to improve soil health or increase plant productivity. The disconnect between discovery and implementation can be attributed to a general lack of standards and agronomic recommendations regarding application rates and techniques. ARS researchers in Corvallis, Oregon, in collaboration with researchers from Oregon State University, have designed decision-support tools that aim to diminish some of the uncertainty regarding the use of biochar on farms. These web-based tools help users learn about biochar, select biochars that are appropriate for their soil needs and farm priorities, and find biochar producers and suppliers. Collectively, these tools will transfer knowledge from researchers to the general public, provide resources, and connect users to regional biochar resources.
3. Biochar can increase the amount of water held in soils. Biochar, a carbon-rich by-product of energy production, has received growing attention as a soil amendment that can improve soil structure, increase crop production, and sequester carbon. However, little is known about how biochar interacts with soil to influence soil water dynamics. ARS researchers in Corvallis, Oregon evaluated the potential for gasified wood and grass biochars to improve soil water retention in a range of Pacific Northwest agricultural soils. Laboratory and field measurements were used to inform a model of field hydrological balance. Under both current and projected climate conditions, the Soil, Plant, Air, Water (SPAW) model indicated that biochar provided benefits for soil water conservation when applied at agronomically-feasible rates. These results indicate that gasified biochars can provide benefits for drought adaptation or water conservation.
4. Inoculated biochar facilitates phytostabilization at abandoned mines. In the western United States, there are over 30,000 abandoned mines that adversely affect soils, watersheds, and rural communities. Phytostabilization is a highly effective method that prevents metals and low pH runoff from entering ecosystems. However, soil conditions at mine sites are not typically conducive to plant establishment because biogeochemical processes select for microbes that create extremely acidic soils and prevent plant growth. Therefore, efforts to remediate mine soils often fail after endemic microbial communities reestablish their populations. ARS researchers in Corvallis, Oregon, in collaboration with other ARS and Environmental Protection Agency researchers, determined that biochar inoculated with beneficial microbes may be able to break the biogeochemical cycles that engender and perpetuate acid mine drainage. This discovery may provide cost-effective options to remediate abandoned mines, improve water quality, and expand biochar markets.
5. The success of rotational crops is a key factor in determining perennial stand length. Grass seed producers in the Willamette Valley of Oregon use crop rotations to manage weeds, control pests, and reduce plant disease prior to establishing a new grass seed crop. Eleven years of remote sensing data indicates that the length and identity of the crop rotation varied greatly. Researchers in Corvallis, Oregon evaluated remote sensing data to determine if this variability was attributable to innate factors, like soil properties or local weather, or if it is attributable to the ability of the rotation to meet management goals. Because researchers found that short rotations and long rotations occurred next to each other, they concluded that soil properties and localized weather were not the primary drivers of crop rotation decisions. Instead, they observed patterns which suggested that the success of the rotation in meeting management goals (weed and pest control) likely prompted decisions to either establish new stands of grass seed crops or to continue cultivating rotational crops. Understanding how growers use rotational crops to meet management goals on a regional level can help increase agricultural productivity in the Willamette Valley.
Review Publications
Okrent, R.A., Trippe, K.M., Maselko, M.B., Manning, V. 2017. Functional analysis of a biosynthetic cluster essential for production of 4-formylaminooxyvinylglycine, a germination-arrest factor from Pseudomonas fluorescens WH6. Microbiology. 163(2):207-217.
Mueller Warrant, G.W., Trippe, K.M., Anderson, N.P., Sullivan, C.S. 2017. An 11-year history of crop rotation into new perennial ryegrass and tall fescue. Seed Production Research at Oregon State University. 153:9-14.
Mueller Warrant, G.W., Trippe, K.M., Whittaker, G.W., Anderson, N.P., Sullivan, C.S. 2017. Spatial methods for deriving crop rotation history. International Journal of Applied Earth Observation and Geoinformation. 60:22-37.
Mueller Warrant, G.W., Anderson, N.P., Sullivan, C.S., Trippe, K.M. 2017. Spatial variability in slug emergence patterns - Third year results. Seed Production Research at Oregon State University. 153:41-45.
Mueller Warrant, G.W., Whittaker, G.W., Trippe, K.M. 2016. Remote sensing of perennial crop stand duration and pre-crop identification. Agronomy Journal. 108:2339-2354.
Okrent, R.A., Manning, V., Trippe, K.M. 2017. Draft genome sequences of seven 4-Formylaminooxyvinylglycine producers belonging to the Pseudomonas fluorescens species complex. Genome Announcements. 5(18):e00277-17.
