On-farm composting for residue managementin Spokane County, WA

SUMMARY
Two compost piles were established on May 14, 2002, of Kentucky bluegrass straw bales broken or water-damaged and not suitable for livestock feed or other uses. A low-input, static pile was 3 feet high and 5 feet wide at one end, increasing in size along its 65-foot length to 8 feet high and 20 feet wide. The size change was to assess the optimum dimensions for composting to occur. Fifteen 4-inch-diameter perforated drainpipes were placed across the pile at 4-foot intervals to increase aeration. During piling, the bluegrass straw was inoculated between layers with soil and mature compost so as to increase microbial populations. The high-input pile was a windrow 8 feet wide, 4 feet high and 555 feet long. Straw bales were positioned using a tractor with a front-end loader and bales were broken up with a bale processor. A windrow established in 2000 was about 600 feet long.

Moisture and temperature readings were taken in 2002 from each of three piles until equilibrium was reached with a Farmex DHT1 brand hay probe at seven marked sites along each pile. In 2003, readings were taken from two turned piles – the mature pile established in 2000 and the new one in 2002 – but not the static pile.

Before spreading the compost, 1-gallon samples were selected from the 2000 windrow to test weed seed viability. The process was repeated in 2003 from the 2002 windrow.

The high-input pile established May 14, 2002, was turned on June 17 and July 25, first with a Caterpillar bulldozer, which tended to push rather than turn the pile, then on June 1 and Sept. 19 in 2003 with a compost turner fabricated from a John Deere 6602 grain combine. The turner worked well as long as the compost was not too wet. Three hundred gallons of aqua ammonia (20-0-0-0) were applied to the new high-input windrow on June 13, 2002.

To determine yield benefit, finished compost from the mature pile was applied in the fall of 2002 at a rate of 48 tons per acre to a nearby eroded hilltop in four replications comparing compost and no compost.

Soil samples were taken from each plot in fall 2002 before spreading compost and again in spring 2003. A mixture of Rod/Madsen soft white winter wheat was planted across the strips with a liquid blend of 80-20-0-20. (The previous crop was lentils.) The wheat was harvested in August 2003.

OBJECTIVES
The goal was to demonstrate effective on-farm composting as a way of managing residue and reclaiming eroded hilltops in an area of eastern Washington with 18 to 22 inches of rainfall.

Specifically, the project sought to:
1. Compare two composting methods for input costs and rate of composting of Kentucky bluegrass straw
a. A static compost pile consisting of layers of straw and soil that was not turned, so it composted slowly (low input)
b. A faster composting method in which a compost windrow is built and turned regularly (high input). Water and nitrogen would be added to speed the process

2. Evaluate mature bluegrass compost as a means of increasing organic matter and crop yields on eroded hilltops.

RESULTS
1. Comparison of composting methods.

The static pile established in 2002 matured little during the project, although it has settled a little and serves mainly as a rodent condo. The compost windrow established in 2000 was mature enough to apply to fields in 2002. The turned windrow established in 2002 achieved a mature consistency (like fine topsoil) in the spring of 2004, ready for application. It took two years to mature under prevailing conditions. The process could be speeded using the combine turner consistently, but moisture will still be a limiting factor.

When the high-input windrow was fresh and newly turned, temperatures at 30 inches inside quickly reached 100 F with a recorded high of 108. Temperatures at individual sites reached 130 and 137 within the first week after turning, but the temperatures were neither universal nor sustained. The optimal temperature to kill weeds with rapid composting is 130-140 F. The next season, when the compost was nearing completion, the maximum average temperature reached 95 F then tapered off. Conditions in the 2000 pile were not hot enough to kill weed seeds. Temperatures in the 2002 pile reached almost 110 F, which may have reduced weed seed viability.

2. Evaluation of mature compost.

Average winter wheat yield in the compost treatments was 64 bushels per acre compared with 56.2 in the check plots, a significant difference. Application of compost also significantly increased organic matter in the first foot of soil. There were no differences in test weight or soil nitrogen in the spring.

Moisture levels never reached the optimal 40% with any piles, remaining in the 25-35% range. Microbe populations are diminished below 40% moisture.

The carbon:nitrogen ratio in the samples was 16.8:1 compared with a ratio in the uncomposted bluegrass straw of 139:1. A ratio in the range of 15:1 to 20:1 is in the neutral range where it neither generates nor consumes N, so soil microbes are able to function at an optimal level. Above 20:1 additional N is needed to digest the carbon. Below 15:1, nitrogen is available and released into the soil.

It is anticipated that as the applied compost breaks down further, more N will become available, providing additional N to crops grown in subsequent seasons. The benefits of increased organic matter should also provide long-term benefits to the soil.

While input costs for the system can be calculated, the amount of compost has yet to be determined, precluding calculation of the cost of making the compost or a cost-benefit ratio. This is being attempted as the compost is used.

BENEFITS OR IMPACT ON AGRICULTURE
While the composting project is still progress, several statements summarize observations and conclusions from the project to date:
1. Waste residue is a valuable product.
2. Crop productivity, at least preliminarily, improved significantly where compost was applied in trial test strips.
3. Organic levels were raised in the eroded areas of the test strips.
4. Compost can be made without manure as a feedstock.
5. Recycled crop waste or plant materials require several years to break down with just turning.
6. Temperatures needed to sterilize weed seeds were not reached.
7. The static pile method was not a satisfactory way to reach the results desired; it took too long to set up and still is not ready to be spread.
8. Transporting compost is a time-consuming and costly operation, so it’s best to make the compost where it’s needed in the field.
9. Turning residue with a locally designed and built grain combine turner significantly increased the efficiency of making compost.
10. Summer rains would have helped speed up the composting process (2003 was a drought year).

PRODUCERS ADOPTION/REACTIONS FROM PRODUCERS
Project coordinator David Ostheller observed that the agricultural community in the area was interested in the project and impressed with the finished compost product.

While local farmers were interested in seeing the project, none indicated they would follow suit on their farms. However, interest is growing in organic grain production as a means of adding value to a portion of the crop as evidenced by attendance at a workshop on organic grain production that Spokane County Extension held in Spokane in January 2004.

It does appear that more people will begin to take an active interest in composting. Indeed, the region has ample bluegrass straw and crop residues that could be recycled on the land as compost.

RECOMMENDATIONS
Ostheller said he plans to pursue organic farming on part of his farm, and this project has helped him to understand the value of plant material as a resource.

“This project has opened my eyes to a whole other world out there that is trying to farm more naturally,” he said. “In our area this was possible when my grandfather farmed, but at great cost in soil erosion.”

He said he also plans to explore making compost tea, a more concentrated nutrient that would be easier to apply. To incorporate more direct seeding and management practices into his farm, Ostheller is designing a drill that will band compost below the seed.

“I hope that with this composting project I will not have to depend on animals to make this system work,” he said.

OUTREACH
The composting project received a fair amount of media attention, including articles in the Capital Press, Western Farmer Stockman and local publications.

In addition, the composting project was a stop on two direct seeding tours for a USDA-SARE research project led by Diana Roberts, area extension agronomist with Washington State University, in June 2002 and June 2003. It was also a stop on a Spokane County Extension tour in July 2003. More than 60 farmers participated in the tours and expressed interest in the project experiments. Fact sheets outlining the projects and results to date were handed out, a poster showing the steps involved was set up and Ostheller demonstrated the compost turner, generating considerable discussion by those attending.