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Protecting Soil and Air Quality

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The ARS soil and air research program protects soil resources essential for U.S. agricultural production, optimizes management of crop nutrients and greenhouse gas emissions from agricultural soils and byproducts, and enhances production management in the face of global climate change. Farms face the challenge of increasing production for a growing population while maintaining profitability, preserving and enhancing natural resources, and instilling public trust. The following FY 2019 highlights demonstrate how ARS helps farmers meet these challenges through research-based practices.

Innovative manure treatment reduces nutrient pollution and creates commercial products. Manure is often used as a farmland amendment to provide nitrogen, phosphorus, and organic matter for crops. Excess phosphorous found in some manures, however, can contaminate rivers, lakes, and bays through runoff. The recovery of phosphorus and proteins from manure prior to application to fields could be advantageous to offset treatment and storage costs, and to lessen the environmental impacts to land. ARS researchers in Florence, South Carolina, developed a new biorefinery process that recovers value-added phosphorus, proteins, and amino acids, and leftover solids from manures. An additional breakthrough came when sugars from sucrose, sugarbeet molasses, and peach waste were used as natural acid precursors to further lower treatment costs. These precursors allowed rapid fermentation, which produced abundant acids. These acids extracted nearly all the phosphorus and the acids also caused nearly all of the proteins to be concentrated in an easy-to-collect precipitate. The process is also effective at extracting phosphorus and proteins from other biological materials such as algae and soybean meal. The recovered proteins can be used to produce amino acids, and the recovered phosphorus can be used as a recycled material to replace commercial phosphate fertilizers. This innovation provides a means to create new revenue stream from farm wastes.

Perennial living mulch systems increase sustainability of corn production. Perennial living mulches are a farming management option that provide the environmental benefits of cover crops, such as reductions in both erosion and chemical runoff, but without the need to replant each year. One plant that is commonly used as a perennial living mulch is kura clover, a long-lived legume that spreads by rhizomes, but the factors affecting its agronomic performance and nutrient management are not well defined. ARS scientists in St. Paul, Minnesota, have been developing the management systems needed to successfully integrate kura clover-based living mulch systems into corn and soy production. They have also developed a novel rotary zone tillage (RZT) system that, in contrast to conventional strip tillage, create 30-cm rows, which more effectively eliminates early season kura clover and reduces corn competition for light, water, and nutrients. The scientists have also shown that due to kura’s nitrogen fixation ability, first-year corn following 2 to 3 years of kura management for forage does not require nitrogen fertilizer to maximize yield and profitability, and second-year corn requires only a reduced application of nitrogen fertilizer. The net economic return from corn grain and stover in the kura-corn system averaged over two seasons was $138 per hectare more than conventional corn production. The combination of the RZT management of the kura living mulch cropping system provides a promising system for corn growers that can return significantly greater economic and ecological outcomes.

Decision support tool promotes adoption of precision agricultural practices on small and medium farms. Auto-guided tractors can reduce on-farm inputs by as much as 20 percent and save producers $10.8 to $13.5 million annually through gains in equipment efficiency and enhanced yields. Moreover, auto-guided tractors also help producers reduce the possible overapplication of fertilizers and herbicides, which in turn reduces the negative environmental footprint of crop production and avoids unintentional input costs. ARS scientists in Fayetteville and Booneville, Arkansas, and University of Arkansas research partners developed a decision support tool that promotes the adoption of precision agriculture technologies such as auto-guided tractors and other self-propelled machinery that reduce overapplication of on-farm nutrients and inputs by 10 to 20 percent. Their Tractor Guidance Analysis software incorporates parameters tailored for the size of different farming operations and generates estimates for 1) reductions in seed, organic and inorganic fertilizer, and chemical inputs given differing terrain attributes; 2) efficiency gains and feasibility of technology adoption by determining break-even prices based on farming operation type, farm size, and capital investment requirements; and 3) subsequent soil health and water quality effects from reduced agricultural inputs based on in-field data. This tool was released in 2018, and scientists have provided hands-on training to farmers and agricultural workers via field days and stakeholder meetings. The Tractor Guidance Analysis software has been especially effective in advancing the use of auto-guided tractors and self-propelled machinery on small farms that have not traditionally adopted precision agriculture technologies.

Adapting anaerobic soil disinfestation (ASD) for commercial production systems. The loss of methyl bromide for soilborne pest control left few registered soil fumigants, and these fumigants are not effective for the spectrum of pests that were previously controlled using methyl bromide. This leaves specialty crop growers at risk. ARS researchers in Fort Pierce, Florida, and their cooperators conducted field trials with commercial producers to assess the efficacy of ASD through a combination of composted or pasteurized pelleted poultry manure and feedstock sugarcane molasses applied under totally impermeable film for crop production without chemical soil fumigation. Use of ASD resulted in yields that were equivalent or higher than those attained from chemical fumigation and demonstrated break-even prices, resulting in consistent, positive returns for growers. Demonstration trials on commercial farms, conducted for multiple crops and seasons, resulted in adoption of ASD, particularly in buffer zone areas in which chemical fumigants cannot safely be applied. This approach provides specialty crop producers with an option for pest control for areas in which they currently have none. ASD requires slight modifications to the pre-plant practices currently employed, but provides economic, worker safety, and environmental benefits.

Reducing phosphorus problems by intensive investigation of best management practices. Although phosphorus runoff from pastures fertilized with animal manure can cause serious water quality problems, long-term studies on the effectiveness of grazing management practices in combination with other best management practices (BMPs), such as rotational grazing, have never been carried out. Scientists from ARS in Fayetteville and Booneville, Arkansas, and University of Arkansas research partners conducted a long-term study to evaluate the effectiveness of grazing management and buffer strips on phosphorus runoff from pastures. The15-year study on 15 watersheds had 5 treatments: hayed, continuously grazed, rotationally grazed, rotationally grazed with an unfertilized buffer strip, and rotationally grazed with an unfertilized fenced riparian buffer. They found that phosphorus runoff was reduced 36 percent with unfertilized buffer strips; reduced 60 percent with fenced, unfertilized riparian buffers; and reduced 49 percent by converting pastures to hayfields. Using buffer strips and converting pastures to hayfields can be effective BMPs for reducing phosphorus runoff in southeastern U.S. pastures. The data can also be used to determine weighting factors for BMPs in phosphorus indices used for nutrient management planning.

Inexpensive vegetative buffers around poultry facilities reduce air pollution. Vegetative environmental buffers (VEBs) are composed of selected trees, shrubs, and/or tall grasses that are frequently installed near the exhaust fans of poultry houses to control and reduce the off-site transport of potential pollutants such as particulates and ammonia. NRCS has historically developed guidelines and tools for the design and selection plants for VEBs, but the effectiveness of VEBs in controlling emissions has not been adequately quantified. ARS researchers in several locations (Florence, South Carolina; Beltsville, Maryland; Lubbock, Texas; and Ames, Iowa) in collaboration with colleagues at universities in Delaware, Iowa, Maryland, Oklahoma, and Alberta, Canada, used state-of-art laser systems and micrometeorological techniques to quantify dispersion and removal of particulates and ammonia from a poultry house surrounded by a VEB. Particulate capture efficiency ranged from 20 percent to 70 percent depending on meteorological conditions; ammonia removal was 22 percent, and net downwind ammonia dispersion was reduced 51 percent. NRCS is using these results to refine and bolster the standards that define the mitigation potential and limitations of the vegetative buffers.