the Effects of Compost Application

SARE FW12-035. (12/31/2013). Comparing organic no-till with conventional tillage methods when direct seeding vegetables and incorporating cover crops. Sustainable Agriculture Research and Education Program, Washington State University, Good Earth. https://projects.sare.org/project-reports/fw12-035/

A two-year study in Western Washington tested organic no-till direct seeding for market garden veggies and showed that no-till beds can be prepared as much as six weeks earlier in the spring than tilled ones, which improves yields throughout the season. The experiment used four treatments on 60'x30' test beds that had not been tilled in the previous two years. This means that the no-till treatment is conducted on a third year no-till bed and the tilled beds showcase the effects of tilling after no-till for two years. This creates a direct comparison of prolonged no-till and the damage just one season of tilling can do. The four treatments were as follows: no-till + manure, no-till + cover crop + manure, tillage + manure, tillage + cover crop + manure. Used in this experiment were fava bean cover crops, chicken manure, and azomite mineral amendments. Year one tested with salad greens and year two tested with carrots.

For the salad greens, the no-till beds produced 150 lbs. more greens than the tilled beds. This is because the start date of planting for the no-till beds was April 9th compared with the tilled bed on June 19th (71 days later). The researchers would like to note that because of the earlier start date and subsequently more cycles of planting greens, the lettuce from the no-till beds is believed to have decreased in nutrients over the season. This a great marker to add for future research replication and verification.

For the carrots, the no-till beds produced 96 lbs. more carrots. The start dates for the no-till beds were two weeks earlier than the tilled beds. What was most astonishing about the carrots was the difference in appearance (see below). The no-till carrots were significantly larger and experienced less splitting and pest damage. This resulted in much more marketable carrots coming from the no-till beds as the tilled beds favored wireworms and rust flies. The researchers hypothesize that the tilling reduced predator populations of these two pests. This is a great marker to add for future research replication and verification. Also, weeding time was reduced by 25% in the no-till carrot beds.

The below soil test results showed a decrease in organic matter, cation exchange, and potassium for all treatment types over the two-year duration. The researchers believe this is due to back-to-back direct seeding of market crops. This is a style of farming they wouldn't normally do and the researchers recommend cycling a year-round cover crop between market vegetables. The soil test results were a bit inconclusive because it is not clarified which bed number correlates to which treatment type, they are only classified as no-till or tilled. It would be great to know what treatment correlates to which bed to better understand the impact of cover crops and manure application. With this information, you can begin to quantify the seasonal effects of certain crops on certain combined management and soil profiles.

Reports with Data:

https://projects.sare.org/wp-content/uploads/984160experiment-results-and-bibliography.pdf

No Till TV: Organic No Till for Vegetable Production by Good Earth (Gary Miller & Amy Plant)

Video: 16:57 - 18:29 Description of aggregates and showing how tillage (even small scale) affects worms. Followed by a description of nematodes and worms and the benefits of no-till.

23:50 Ribbon test for clay-rich soils.

SARE GW19-202. (10/31/2020). Climate mitigation through soil carbon sequestration: increasing soil resilience and plant productivity on rangelands through compost application. Sustainable Agriculture Research and Education Program, Western State Colorado University. https://projects.sare.org/project-reports/gw19-202/

"Climate change has already shifted temperature and precipitation levels in Colorado, making it hotter and drier." Typically, ranchers in the West harvest three cuts of hay during the season. However, in some locations in Colorado, like Gunnison, they only get one harvest. "The soil microbial community can play an integral part in increasing nutrient availability to enhance plant production and the C sequestration potential of soils." Through this project, the researchers aimed to understand how compost application increases the C sequestration potential of rangelands, if compost additions enhance SOM to increase a soils water holding capacity (WHC), and what is the correlation between compost additions, soil microbial community structure, and soil C sequestration.

The study was conducted at four test sites on perennial semi-native pastures in the Gunnison Valley in Southwestern Colorado. "The plant communities in these rangelands are domesticated by: Meadow Foxtail (Alopercus. prratensis), Kentucky Bluegrass (Poa pratensis), (Trifolium hybridum L), Dandelion (Taraxacum officinale). Known and present invasive are Curly Dock (Rumex crispus), Canada thistle (Cirsium arvens) and Prostrate Knotweed (Polygonum aviculare). The soils in this area are comprised of a Mysten series, which consist of excessively drained soils that formed in neutral or slightly acid sandy alluvial sediments derived mainly from granite (National Cooperative Soil Survey, 1975)." All four ranches are within 30 km of each other. The sites are all flood irrigated from early June to August 2019, but are grazed at different durations, frequencies, and densities. Compost, "GunniGold," a Class A bio-solid was applied to all sites from June 17th to June 21st, 2019, at a rate of 5cm per treatment plot (T1-5). The data collected from each site included drone footage, species diversity, biomass harvest, soil properties, field soil moisture, soil organic matter, soil organic carbon, and followed with statistical analysis.

In one year (2019-2020), four ranches in Western Colorado saw a 23% increase in soil organic matter across all sites and an average 66% biomass boost at 3/4 treatments after adding two inches of compost to their rangeland. For most of the growing season, there was a trend of increasing soil moisture relative to the control plots. For parts of the season, there was not a significant difference in soil moisture between treatments and control groups. The composted plots were preferred by cattle over control plots. The compost used for this experiment was a class A biosolid, or, the result of a wastewater treatment plant that produces compost.

SARE GS19-209. (08/31/2022). Improving resilience, sustainability and nutritional properties of specialty crops using composted spent coffee grounds. Sustainable Agriculture Research and Education, Texas A & M University. https://projects.sare.org/project-reports/gs19-209/

This research looks at a "key component of sustainable agriculture" - waste utilization. By testing if spent coffee grounds (SCG) can be used as a substitute for peat in potting mixes, a new pathway in waste recycling can be created. Peat releases CO2 when harvested, so SCG could be more eco-friendly and generate a local circular economy. The study tests how non-composted and composted SCG affect plant growth, germination, and carotenoid levels as a source of ammonium and nitrate when added to soil.

The experiment used three different treatments of the SCG - fresh, static-pile composted, and EcoDrum composted. These three coffee ground treatments were mixed with potting soil at the following rates: 10%, 25%, 50%, 70%, and 90% coffee ground:potting soil. The spent coffee grounds came from a cold-brew coffee company based in San Antonio, Texas. The non-composted SCG were collected from the delivery pile within 24 hours of drop-off, dried, cooled, and stored indoors in a plastic container. The Static-Pile composted SCG were removed from the delivery pile within 9-months of drop-off, brought to temps of 100˚-140˚F, dried for 48 hours, and sieved to 2mm before being stored indoors in a plastic container. The in-vessel composted SCG were taken from the initial dump pile to the Texas A&M Ecodrum in-vessel composter. The process began with four 200kg barrels of fresh SCG added to the Ecodrum. Subsequently, a barrel of fresh SCG was added every other day for 21 days. Then, turning was reduced to biweekly for 90 days.

Experiments with peas, spinach, radish, eggplants, and basil in the different ratios of SCG to potting mix, static-pile composted SCG to potting mix, and in-vessel composted SCG to potting mix, were used to test each mixtures capability. To measure success, the researchers used height of plant, number of flowers and fruit, fresh weight, fruit weight, fruit length, and dry weight.

The first experiment looked at germination rates in sugar snap peas, spinach, and radish planted in the three coffee ground treatments and subsequent six different ratios. With the peas, the research saw a decrease in days to germination in treatments of 50% composted SCG. With spinach and radish, there was a decrease in days to germination and a higher germination rate at 75% static-pile composted SCG than any other treatment. Ultimately, "composted SCG can be used as a biostimulant and partial peat replacement for these particular species."

The second experiment focused on growth of eggplants and basil within different treatments. With eggplants, they found that 10% composted SCG to potting mix resulted in a significantly higher biomass than the control, but between 10%-50% composted SCG did not change yields. When using ratios of non-composted SCG, the eggplant growth and development was significantly reduced in all treatments. With basil, they found no difference in biomass between 10%-25% composted and non-composted SCG. They also found that the control had higher biomass production than the 10% composted SCG mixture. Ultimately, the basil died in all non-composted SCG treatments greater than 50% SCG.

When testing mineralization rates, the researchers concluded that SCG are slow to mineralize N. They found that higher microbial activity is present to breakdown SCG as evidenced by higher levels of CO2 respiration.

Ultimately, composted SCG can partly replace peat without harming plant growth at species-specific rates. Non-composted SCG can stunt growth.

SARE LS99-099. (12/31/2002). Economic and Environmental Effects of Compost Use for Sustainable Vegetable Production. Sustainable Agriculture Research and Education, Virginia Polytechnic Institute and State University, Virginia Coop Extension, Northern Piedmont Agriculture Research and Education Center. https://projects.sare.org/sare_project/LS99-099/?ar=1999

The study in Southern Virginia looked at how compost, manure, and fertilizer affect soil biology, chemistry, and physical properties through metrics like nutrient leaching, runoff, average yields, and economic return. In Virginia, conventional farms rarely use compost and only apply manure for nitrogen content. Additionally, conventional farms are "designed to optimize soil fertility by adding inorganic fertilizer on the basis of soil testing." However, "the availability, not the total amount of essential nutrients in the soil, limits crop production (King, 1990)."

This study replicated eight treatments on three farms. The treatments were:

• CTL - control = no amendments

• LC - low compost = 20% of agronomic N need met with compost.

• LCF - low compost rate with supplemental fertilizer = 20% of agronomic N needs met with compost, fertilizer used to meet the needs of N, P, K.

• AC - agronomic compost rate = N needs met fully with compost.

• BC - agronomic compost rate applied biannually.

• BCF - agronomic compost rate applied biannually with supplemental fertilizer for N, P, K.

• PL - poultry litter = N needs met with PC.

• F - agronomic needs met with fertilizer only.

Winter Rye was the cover crop and was incorporated into the soil each spring by disking. Over the three years this experiment was conducted, pumpkin, sweet corn, and bell pepper were grown.

What is of most interest for Close the Loop - Clark County, WA, are the soil types used in this study. Clark County is made up of mostly silt loam, clay loam, loam, gravelly loam, and cobble silt loam. This research was conducted on silty clay loam and silt loam.

To go even deeper, what these soils in Virginia share in common with the soils of Clark County, WA, is some of their parent material. Soils are made up of non-organic and organic parts. It is important to know the underlying bedrock of soils to understand the regional soil chemistry. The non-organic parts of the Virginia soil series derive from predominantly siliciclastic (26%), metamorphic (28%), and plutonic rocks (20%), with a small percentage of carbonate (2%) and volcanic rocks (2%) (https://macrostrat.org/sift/#/column/367). This creates an environment rich in diabase, basalt, gabbro, greenstones derived from metamorphosed sedimentary and volcanic rocks, and clay. In Clark County, we are surrounded by soils whose non-organic parts derive from siliciclastic (57%) and volcanic rocks (40%) (https://macrostrat.org/sift/#/column/268). This creates an environment rich in volcanic ash (oxidized minerals), basalt, andesite, diorite, gabbro, and alluvium. "The deposits of sand and gravel in the recent alluvium of the East Fork and main branch of the Lewis River, as well as the Pleistocene terraces associated with these rivers, are the result of transportation of sediments from the Southern Cascade mountains. These rocks, mainly andesites, basalts, pyroclastics, and sediments... have not been highly weathered and are fairly hard (https://www.dnr.wa.gov/publications/ger_ofr75-11_sand_gravel_clark_co_62k.pdf)."

The similarity of parent material - basalt, gabbro, and clay - means that there are similar mineralogical components to the soil profiles from both areas. The chemical non-organic portions of soil can be very telling as to what soil amendments are needed to sustain plant growth. For instance, soils derived from mafic materials - like those in Clark County and this SARE experiment - tend to be more acidic, needing inputs of limestone (Ca) to neutralize pH for plant growth. Additionally, the chemical make-up of the non-organic parts of soil impact the CEC, pH, ionic strength, types of ions in solution, and ultimately impact rates and ability of aggregation. Knowing these soils have similar geologic origins, with Virginia experiencing more regional metamorphism, it is fair to consider the research results as a more accurate forecasting to how Clark County soils can behave with compost amendments. Below are the soil profiles of Clark County and the SARE-researched Virginia soil series. Important to note, the Jackland loam is the most similar to Clark County soils, the Weaver silt loam is similar in texture, but is more felsic than the silt loams found in Clark County, and the Fauquier series is the least geochemically similar of the Virginia soils.

Most common Clark County Soils: https://clark.wa.gov/sites/default/files/dept/files/public-works/Stormwater/Regulations_Codes/CCWWHMSoilGroupMemo.pdf

Clark County, Washington Open Data

The Olympic series consists of very deep, well drained soils formed in residuum and colluvium weathered from basic igneous rocks. Silty clay loam, forest.

• Parent materials include basalt, andesite, and less commonly diorite and gabbro.

All of the following soil series formed from alluvium. The alluvium of Clark County is derived of andesite, basalt, and pyroclastics.

The Lauren series consists of deep, well drained soils formed in alluvium and loess containing volcanic ash. Gravelly loam, pasture.

The Wind River series consists of very deep, well drained soils formed in an alluvium or outwash. Located on terraces. Fine sandy loam, cropland.

The Hillsboro series consists of deep, well drained soils formed in mixed alluvium. Silt loam, cultivated.

The Hesson series consists of very deep, well drained soils that formed in mixed alluvium. Clay loam, pasture.

The Sauvie series consists of deep, poorly drained soils that formed mainly in alluvium. Typically located on floodplains. Silty clay loam, cultivated.

The Hockinson series consists of very deep, somewhat poorly drained soils formed in alluvium. Loam, pasture.

The SARE-researched soil profiles:

NPAREC on Faquier silt clay loam: The Fauquier series consists of very deep, well drained soils that have moderate permeability. They formed in material weathered from greenstone and similar mafic rocks. Silty clay loam, mixed hardwood forests.

Bracketts farm on Jackland silt loam: Soils of the Jackland series are very deep, moderately well drained and somewhat poorly drained with very slow permeability. They formed in residuum that weathered from diabase, basalt and gabbro of the Northern part of the Piedmont plateau. Silt loam, mixed hardwood and pine forest.

Cascades farm on Weaver silt loam: The Weaver series is a member of the mesic family of Fluvaquentic Eutrudepts. Contains lime nodules. Silt loam, cultivated.

Experiment breakdown and results:

Soil Health indicators:

At Brackett's farm, on the Jackland loam, the background nutrient levels of P, K, and Mg were high initially. "The initial K base saturation of 22.5% was two to four times higher than the other sites." The BCF treatment had higher concentrations of P, K, and Mg and CEC than the control, fertilizer, low compost treatments, and BC. However, it is worth noting that the "treatment randomization placed the BCF treatment at the end of each row where higher amounts of nutrients existed." Within the AC and BCF treatments, the pH was raised compared to all other treatments. The AC, BC, and BCF treatments had higher C and N concentrations than the CTL and F. At all sites, low compost rate treatments did not have a considerable difference in N and C values than the CTL and F treatments.

Comparatively to other sites, Cascade farm on the Weaver silt loam had higher CEC, organic carbon, calcium and pH to start. In the first year, Ca dominated the CEC, but decreased in all treatments except the CTL after the initial amendment application. Within the AC, BC, and BCF treatments, the concentrations of P, K, and Mg increased with time and had higher concentrations than the CTL, LC, and F treatments. No difference in CEC was measured. Nitrogen and organic C concentrations were highest in the AC treatment. At all sites, low compost rate treatments did not have a considerable difference in N and C values than the CTL and F treatments.

Across all sites, soil bulk density was lower in the AC, BC, and CF than in the CTL and F after the second and third growing seasons. Higher bulk densities tend to indicate a more compacted or denser soil. A reduction in soil bulk density trends towards a good thing, especially for clay rich soils. Additionally, even the LC and LCF rates lowered soil bulk density. This shows the correlation between bulk density and organic C additions. The third year of the experiment showed the first indicator of a difference in soil water content among treatments - the AC, BC, and BCF treatments held more water than other treatments. This proves that the compounding years of organic amendments increases soil water holding capacity.

Yields:

Across the board, no treatment effects were noticed for first year pumpkin yields. This supports the idea that it takes time to see the benefits of compost application. In the second year, the Jackland series corn yields had no difference among treatments and it was a low-productivity year due to natural circumstances. "These factors inlcuded excess early soil moisture that reduced germination, seedling vigor, and N availability; poor farm management (i.e. irrigation timing and weed control); and severe mid- to late-season soil moisture deficit plus excessive heat." For the Weaver series, the corn yields of year two were relatively high, but there was not a significant difference among treatments. In year three the Jackland loam saw low yields and no improvement with three years of treatments. Coinciding with poor farm management was a late spring frost and mid-season drought. "The Jackland loam soil is an inherently low productivity soil and even three annual applications of compost at agronomic N rates were not sufficient to improve productivity." The Weaver series saw high yields, but due to its initial high concentration of soil C and ample water table, the naturally productive soil did not benefit from any treatments. It was observed that the AC and PL treatments had the highest Rye biomass with the AC treatment producing 3x the biomass of the CTL.

Overall, the project outcomes resulted with high annual application rates of compost improving soil physical and chemical properties, but crop yields were only improved in places where native soil productivity is not extremely high. The amendments with a combination of high organic matter and nutrient availability produced the highest crop yields (high compost rates, compost + fertilizer, and poultry litter). "Low annual compost rates provide little advantage over the unamended soils."

The most important result to be aware of are the soil phosphorus levels when using organic materials as a nitrogen source. The recommended Virginia Tech P2O5 levels are 100lbs/ac. The following are the average results of the experimental treatments:

• LC + LCF = 128 lbs/ac

• AC = 638lbs/ac

• BC and BCF = 843 lbs./ac

• PL = 202 lbs/ac

Throughout this experiment, the quantities and prices of most inputs were recorded in addition to the hours of labor invested in each management practice. Ultimately, the mean gross margins are negative or zero except for the pumpkin control fields. "Only seven plots in the experiment produced enough yield to cover the variable cost of production," although the "labor investment in these small plots is considerably higher than would be expected in a commercial operation." The mean gross margins declined from 2000-2002 for all treatments except AC and BC. The researchers found that the cost/acre was high because straw mulch is expensive, the price of compost is high, and the scale of the operation made insufficient use of the capital and labor available.

SARE OW20-358. (12/31/2023). Compost for Carbon Sequestration on Irrigated Pasture. Sustainable Agriculture Research and Education Program, Colorado State University Extension. https://projects.sare.org/project-reports/ow20-358/

This project studies the use of compost on rangelands in Western Colorado as a way to store carbon and involve ranchers in fighting climate change. The project builds on existing California research that showed compost improves soil and plant growth. The experiment, with trials at two locations, tests the effects of a single compost application on grass productivity, carbon storage, and and species composition. The three different treatments used are compost, compost and fertilizer, fertilizer only, and control plots.

The compost was applied in 2021 and soils data was collected in spring of 2022 and 2023. Rather than applying at a rate of (# of inches of compost)/acre, the researchers applied the compost based on a per ton basis, quantified by the nitrogen demand of crops relative to the available nitrogen in the compost. The end result soils data has not yet been released.

However, of interesting note, stakeholders, especially local producers who manage the land, are actively involved in evaluating the practice of compost application and identified compost quality as an important factor to learn more about. Because of this, the research team sampled four industrial compost for salts, nitrogen, and other nutrients, and chemical characteristics. The link to the results are found here: https:/ty/projects.sare.org/wp-content/uploads/Compost-Data-Handout.pdf . From their results, they found that compost made from chicken manure was much higher in salts. This was useful because some areas in Western Colorado already have high salt content in their soils. Conducting something like this for regional compost facilities may be of use for WA farmers to better select compost that fits their soil chemistry and land use needs.

SARE SW99-008. (12/31/2003). The Transition from Conventional to Low-Input or Organic Farming Systems: Soil Biology, Soil Chemistry, Soil Physics, Energy Utilization, Economics, and Risk. Sustainable Agriculture Research and Education Program, Colorado State University Extension. https://projects.sare.org/project-reports/sw99-008/

Over a 12-year study, organic farming doubled soil carbon over 10 years and was the most profitable compared to conventional methods. "Runoff from cover-cropped systems was 1/3 that from conventional systems. The conventional farming systems were least efficient at storing excess N." Despite lower yields, organic and low-input farming practices are gaining popularity due to environmental and health concerns, with the Sustainable Agriculture Farming Systems (SAFS) project at UCDavis exploring alternative strategies like cover cropping for sustainability. The results show that while organic yields were about 10% less than conventional, they achieved higher prices. Plus, both organic and low-input systems maintained yields with significantly reduced pesticide use. Additionally, it is important to note that the average difference between yields of organic versus conventional agriculture are less than the year-to-year variation of annual county averages for each crop.

One of the main drivers of this research is Pm-10 being recognized as an air quality concern. Pm-10 is particulate matter with a diameter of 10 micrometers or less. This dust can be produced from agricultural practices and causes respiratory issues in humans. Increasing soil health can reduce erosion of all kinds, decreasing Pm-10 production as a result. Additionally, some other issues of focus for this research is Agriculture being the largest consumer of water and main source of polluted runoff in California. Ultimately, Agriculture must change production to either cut costs or increase yields, or both.

The soil types at the Agronomy Farm of UCDavis are the Reiff Loam and Yolo Silt Loam. Looking at Davis, California on MacroStrat.org, you can see this valley is composed of siliciclastic, carbonate, and volcanic material (tuffs, or, a mixture of volcanic debris and ash.) As stated in the annotated bibliography for SARE LS99-099, the soils of Clark County have parent materials composed of siliciclastic and volcanic rocks. This indicates that not only are the soil textures similar at this site location, but the non-organic chemical and mineral components are similar.

The treatment types for this project are as follows:

Three, four year rotations: growing tomato, safflower, bean, and corn.

• Conv-4: using the typical management practices of the surrounding area. Use of synthetic fertilizers and pesticides. No cover crops.

• Low-input: fertilizer and pesticide inputs were reduced with use of legume cover crops and mechanical cultivation for weed management.

• Organic: managed according to the regulations of California Certified Organic Farmers (1995). So, no synthetic chemical pesticides or fertilizers. Used were cover-crops, composted animal manure, mechanical cultivation, and limited use of approved products. One, two year rotation:

• Conv-2: using the typical management practices of the surrounding area. Use of synthetic fertilizers and pesticides. No cover crops.
  

Results:

• Low-input yields for tomato, safflower, and corn averaged 97%, 84%, and 108% of conventional plots, respectively.

• Organic yields for tomato, safflower, and corn averaged 88%, 90%, and 94% of conventional yields, respectively.

• For this experiment, the conventional yields were higher than the county average.

• They found more diseases in the Conv-2 rotation than the Conv-4 rotation.

• Ultimately, pesticide use can be decreased by half with little to no decrease in yields.

• "Management systems that rely on organic inputs as sources of fertilizer have different dynamics of soil nutrient availability than systems receiving mineral sources."

• "Understanding soil biology is especially important in cover crop systems, which rely on below-ground biota to liberate plant nutrients."

• https://pdfs.semanticscholar.org/6c9c/d8f268d784134cf459bfa0f47cf3889aad90.pdf

For the economic and risk component of this research, costs, returns, and profits were used to simulate the economic performance of a hypothetical 810-ha (2000 acre) farm based on the current prices within the region (1995). They used the American Society of Agricultural Engineer's formulas to calculate the costs of equipment, fuel, lubrication, and repair. The link to the economic results (pp.34-42) are no longer found online - no conclusions available.