Project : USDA ARS

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Research Project: Improving Plant, Soil, and Cropping Systems Health and Productivity through Advanced Integration of Comprehensive Management Practices

Location: Forage Seed and Cereal Research Unit

2019 Annual Report

Objectives
The long-term aim of this project is to address strategic, high priority needs of grass seed growers in the Pacific Northwest (PNW) by assessing and developing management practices that simultaneously improve crop productivity and advance soil health. This aim will be met by interrogating research questions that fall into two broad objectives. The first objective is primarily focused on improving crop production by lessening the overall impact of pests, weeds, and pathogens, improving the arability of marginal lands with novel soil amendments, and assessing the impacts of management practices on soil health and fertility. Objective 2 also aims to improve crop productivity by identifying key interactions between genetics, environment, and management (G x E x M). Within this objective, tradeoffs between intensifying production and advancing ecosystem services are quantified and better understood to help farms reach and sustain their potential, including the impact of crop rotation and other management practices on increasing populations of beneficial microbes and improving soil health. Collectively, Objectives 1 and 2 advance our understanding of how G x E x M interactions impact agroecosystem productivity and resilience. For Objective 3, these data will be synthesized and developed into decision-support tools and models to provide growers with concrete strategies for improved land management and cultivation of grass seed cropping systems. Objective 1: Identify and evaluate management practices that improve crop productivity and crop health or that enhance environmental quality. - Sub-objective 1A: Identify technologies to reduce priority pests, diseases, and weeds that limit the profitability and sustainability of the cropping system. - Sub-objective 1B: Assess the environmental and production outcomes from the application of biochar on marginal soils. - Sub-objective 1C: Determine the effectiveness of crop rotation in reducing populations of weeds, diseases, and invertebrate pests. Objective 2: Identify and assess key interactions between cropping system, environmental conditions and management practices that influence cropping outcomes and agroecosystem productivity. - Sub-objective 2A: Evaluate the impact of management practices, including crop rotation, on soil health parameters. - Sub-objective 2B: Assess the impact of cruciferous crop rotations on plant growth and microbiomes. Objective 3: Develop knowledge and decision support tools that enable growers to optimize production. - Sub-objective 3A: Develop and expand decision support tools that provide information about biochar to growers. - Sub-objective 3B: Develop models and decision aids that improve soil health and improve system productivity by decreasing the yield gap. - Sub-objective 3C: Develop strategies to reduce priority pests, diseases, and weeds and improve soil health.

Approach
The overall hypothesis of the project is that improved cropping practices in grass seed cropping systems provides simultaneous benefits to soil health and crop productivity. This hypothesis is tested within three objectives and their related subobjectives. In Objective One, we explore methods to reduce the populations of weeds and pests that limit productivity. This research is conducted in laboratory, greenhouse, and field experiments that determine if practices that promote soil health and lessen environmental impacts (application of soil amendments, selective herbicide application, and precision weed management) are detrimental or beneficial to crop yield. In Objective Two, the research aims to determine if conservation practices (cover cropping and reduced tillage) improve soil health, and if soil health can be attributed to improvements in crop yield. These objectives are met with laboratory, greenhouse, and field experiments that assess soil health and identify allelopathic responses mitigated by cover crops. The aim of Objective Three is to synthesize the information gathered in Objectives One and Two, and to create decision support tools that enable growers to optimize production. These tools will be provided to growers as web-based tool kits, models, or agronomic measures used to control pests, pathogens, and weeds, and to apply soil amendments. In general, these approaches aim to identify key interactions between genetics, environment, and management that simultaneously reduce farm inputs and improve ecosystem services by identifying and quantifying tradeoffs.

Progress Report
This project began in September 2018, and continues research from 2072-21410-004-00D and 2072-22000-042-00D. Progress under Sub-objective 1A developed methods that will be used in subsequent years to advance our understanding of how marginally-selective herbicides can add to the arsenal of tools to control persistent weeds, including roughstalk bluegrass (RB, Poa trivialis). Data collected by grid sampling in a tall fescue seed field was used to produce a series of maps with the intention of targeting areas of RB infestations for control with the marginally-selective herbicide, glufosinate. Marginally selective herbicides can kill weeds, but may reduce crop yield. However, because seed prices were unusually high, the grower chose to not apply glufosinate to avoid yield loss. This prevented estimation of yield loss due to herbicide damage. It did, however, simplify the analysis to determine the effects of RB competition on tall fescue seed yield. Three fields were analyzed for relationships between combine yield monitor data, ratio of roughstalk bluegrass seed to tall fescue seed in windrow and combine seed hopper samples, and roughstalk bluegrass severity across the field. These analyses confirmed that the presence of RB populations significantly decrease tall fescue seed yield, and in some cases over 50 percent yield losses were measured. Weed maps were subsequently developed using combine yield monitor and ground truth data and provided to growers to control RB populations as described in Sub-objective 3B. Pyroligneous acid (PA) is an industrial byproduct that has the potential to control soil-borne phytopathogenic fungi. Progress under Sub-objective 1B demonstrated that PA is able to control the growth of Verticillium (V.) dahliae, a prolific plant pathogen, in vitro at very low concentrations. Experiments in the laboratory determined that PA-mediated control of V. dahliae is achieved regardless of the fungal life stage (vegetative mycelia, conidia, or microsclerotia). However, control of Microdochium nivale, the causal agent of Dollar Spot on turf grass, was not achieved using similar concentrations of PA. Ongoing experiments aim to validate these experiments in soil with a broader range of fungi. 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. These impacts are especially evident on marginal soils, including abandoned mine sites and metal-impacted agricultural soils. Progress under Sub-objective 1B was made to determine which biochars adsorb metals from soils. Soils were collected from a grass seed field in Idaho with concentrations of lead and aluminum that far exceed regulatory standards. Laboratory experiments using methods developed by the Environmental Protection Agency determined that biochars produced at high temperatures with a smaller particle size were ideal for absorbing metals. These data were used to design and implement a field experiment at an abandoned mine site in southern Oregon. The aim of the field trial is to determine if blends of amendments (lime, municipal biosolids, biochar, and microbial inoculum) outperform the business-as-usual model of adding lime. To facilitate this experiment, methods to culture endemic microbes from the nearby ecosystem were explored, including producing inoculum from organic matter and directly adding soil collected from the rhizosphere. Initial greenhouse trials indicated that inoculum cultured from different sources ultimately influenced the microbial rhizosphere populations. Ongoing analyses will determine if these methods are efficacious in field and greenhouse trials. The Juniper Biomass Optimization Project, a subordinate project relevant to Sub-objective 1B, investigated whether juniper encroachment, which is degrading rangelands throughout the Western U.S., can be economically treated as part of a biomass utilization framework involving biochar. The study focused on Wheeler County, Oregon, where the Soil Water Conservation District has initiated juniper removal on thousands of acres of private land. A biomass inventory component of the study developed critical improvements in inventory methods, using remotely sensed data gathered from Light Detection and Ranging, Geographical Information Systems, and Unmanned Aerial Vehicles resources. A harvest logistics component of the study developed algorithms that predict merchantable value of harvested biomass and identified areas where juniper removal is most economical. An economic analysis evaluated biochar production with a range of technologies, from hand-operated kilns to semi-stationary continuous-throughput units, and showed that all of these approaches can be profitable within five years, if markets can absorb the large quantities of biochar produced. Scientists in Corvallis, Oregon, also evaluated if juniper biochar can facilitate native bunchgrass reseeding in a pilot greenhouse study and two-year field trial. The greenhouse study indicated that juniper biochar can double germination rates by enhancing soil water content, but only if the biochar is tilled into soil, which is generally incompatible with restoration practices. The field study showed no improvement with biochar. Additional hydraulic modeling indicated that applying biochar on the soil surface improves soil moisture much more than tilling under extended drying. Ongoing research conducted under Sub-objective 3B.1 will facilitate the expansion of the Pacific Northwest Biochar Atlas, an online biochar decision support toolkit. New technologies to produce biochar were demonstrated in conjunction with industrial partners. Several biochars were obtained from this demonstration, and from other regional biochar producers. In addition, biochar was produced from novel feedstocks, including grape vines. Each biochar was characterized for physiochemical properties using International Biochar Initiative standards. These data will ultimately connect regional biochar users and producers by allowing users to identify biochars that ameliorate specific soil deficiencies or that meet other agronomic goals. Documenting crop rotation histories in the Willamette Valley can enable scientists to identify rotations that lead to positive cropping outcomes. Under Sub-objective 1C, significant progress was made in developing accurate landuse classifications to facilitate cataloging and analyzing multi-year crop rotation histories. Gaps in Landsat 7 imagery were repaired using statistical methods. Using these methods, more precise histories of crop rotations were obtained from satellite data. An independent database of approximately 200 fields whose detailed management history has been provided by cooperating growers has been created. Likewise, all crop rotation data was made publicly available through data repositories. Grass seed production in Willamette Valley (WV) of Oregon has traditionally employed practices that are known to degrade soil quality, including annual tillage and removal of crop residues. However, over the past few decades, a subset of growers has implemented conservation-oriented cropping practices that favor soil health, including high-residue loading, crop rotation, and infrequent tillage. While the soil benefits are evident to the seed producers who have adopted conservation-oriented practices, these benefits have not been observed in field studies. As a result, these practices have not been adopted by the broader seed cropping community. Significant progress was made under Sub-objective 2A to better understand how conservation-oriented production methods impact soils over a decadal time frame. To accomplish this, a pilot study was designed and conducted to: 1) validate grower observations that soil health and carbon accumulation is linked to duration of conservation management; and 2) determine the number of fields needed to detect a statistically significant correlation in the expanded year two chronosequence study. In the FY19, interviews with seed producers were conducted, and soil samples collected from fields managed under conventional or under conservation practices. These samples were analyzed for a broad suite of soil health metrics. Preliminary results indicate that conservation practices are linked to improved soil health scores; however, subsequent analyses are necessary to validate these results and to disentangle relationships between soil carbon accumulation and microbial activity. Progress was made under Sub-objective 2B. Cruciferous species produce a suite of well-known allelopathic compounds that alter the soil microbiome, including glucosinolates and isothiocyanates (ITC). These compounds alleviate pathogen pressure in several cropping systems. The ability of ITCs to positively select for beneficial microbes, including plant growth promoting rhizobacteria, is not well understood and has not been studied in seed cropping systems. Growers have reported larger yields in fields post-brassica rotation and when volunteer brassicas emerge in recently planted stands of perennial grasses. To determine if the presence of brassica species improve the growth of seed crops, a bacterial biosensor that detects the presence of ITCs in the rhizosphere was developed. Dose response curves indicated that the biosensor would be useful in determining biologically relevant concentrations of ITCs in soils. Thus, the biosensor is being deployed in ongoing greenhouse experiments to determine if ITCs are produced in the rhizosphere, if allelopathic impacts promote the growth of annual ryegrass, and if those effects are best realized through crop rotations or through intercropping with ryegrass and cruciferous crops.

Accomplishments
1. Surface soil moisture content and rainfall timing define slug emergence patterns. Slugs are persistent and serious pests in grass seed crops, and primarily cause damage to young grass seedlings. Producers of grass seed crops struggle to effectively control slugs with metaldehyde and iron phosphate baits due to their rapid removal from the soil surface by earthworms, bait weathering, label restrictions, and cost of the product. Knowledge of when slugs are active can help target bait applications to times when it will be most effective. Results from four years of detailed field plot studies by researchers in Corvallis, Oregon, were used to derive a regression model quantifying the impact of surface soil moisture content and rainfall on slug emergence patterns. Slug counts increased proportionally with soil moisture content. Improved specification of the soil moisture factors defining slug emergence patterns will help growers know when to start intensively monitoring their fields and to better anticipate the timing and numbers of slugs likely to appear in new plantings.

2. Repair of gaps in Landsat 7 imagery improves accuracy in classifying landuse in a complex landscape. Limited supply of high-quality satellite imagery is a critically limiting factor in accurate remote sensing classification of crops and other landuses across wide areas. Mechanical failure of a rotating mirror in the satellite Landsat 7 on May 31, 2003, resulted in data gaps covering 22% of the viewing area. Limitations inherent in all earlier procedures to fill in these missing gaps were overcome in a new method, Multi-Step Block Mapping on Principal Component Uniformity, developed by researchers in Corvallis, Oregon. Applying this method to the complex landscape of western Oregon approximately doubled the number of useful images available for remote sensing classification of crops and cropping sequences over a 14-year period. These new classifications have improved year-to-year consistency, allowing scientists to better characterize crop rotation sequences and more accurately measure perennial crop stand life. Detection of events such as the need to replant grass seed crops after failure of crop stand establishment will allow future research to be better focused on the most problematic conditions faced by growers.

3. Model impact of climate change in western Oregon with the Soil Water Assessment Tool (SWAT). Climate change has the potential to drastically impact crop production and ecosystem services through alterations in temperature and precipitation patterns. SWAT is a well-developed, commonly-used model for studying the impact of environmental factors on crop production across landscapes, including the off-site movement of sediment and nutrients from fields to streams, rivers, lakes, and reservoirs. Scientists in Corvallis, Oregon, used Soil Water Assessment Tool (SWAT) to model the consequences of climate predictions that alter wintertime precipitation in western Oregon from the current rain-snow mixture to rainfall-dominant conditions on soil erosion. This transition is interpreted by SWAT as leading to drastically increased soil erosion and sediment transport in the area’s streams and rivers. Additionally, the results of the model suggest that that farmers will likely have to make changes in their choice of crops grown based in part on which ones tolerate the warmer weather and altered precipitation patterns.

U.S. DEPARTMENT OF AGRICULTURE

Forage Seed and Cereal Research Unit: Corvallis, OR