Farm Calls: Aerated Compost Bins on a NJ Farm

We visit with a NJ tree fruit grower who has instituted an equine manure management plan for his farm.
For a change of pace, on this farm call we asked the questions.

What benefits have you observed applying compost to your crops?
How did you go about constructing your compost bins?
Was it worth the effort?

Crop Benefits

What benefits have you observed applying compost to your crops?
Composts applied to my orchard soils, under the tree canopy, result in tree growth and performance benefits greater than what would be explained by the composts’ fertilizer value of nutrients alone. Trees have a larger caliper (diameter) at a younger age.

Weeds suppressed under the canopy (without herbicides) may account for part of this increased tree growth rate. This includes suppressing competitive yield robbing perennial weeds like nutsedge. While I am not organic, and do not believe in organic orchard production, I can manage acres of fruit with a backpack sprayer spot herbicide applications.

I also sense there is improved soil moisture retention in the orchard, also contributing to tree growth.

None of these observations depend on claims that compost improves soil biological health, which improves crop performance, but I definitely believe this to be true. Nature does not like bare soil. Traditional clean-cultivated soil under canopies is not the best way to grow fruit trees. Soil performs better covered, and compost in the orchard enables me to suppress weeds, retain moisture, and improve tree performance with covered soil.

Bin Construction

How did you site your aerated bins?
I started with an overall manure management plan complying with NJ manure regulations. To determine the best location for the bins, I chose a flat area that was not wet, subject to run-off, and away from environmental concerns. The area is close enough to electric, water, and the source of the manure I need to manage. It’s a large enough area to work with equipment, like loader, spreader, and trucks. The work area has an all weather surface; I chose gravel but a concrete pad would work as well.

How did you determine the size and number of bins?
I measured the cubic feet of material generated per day. A single bin should be large enough to handle two weeks of material. Manure placed in bins starts its biological composting in about two weeks. A two-week filling time maintains consistent bin temperature, consistent batch composting, and consistent quality composts. Expect compaction of the bedding material (e.g., straw will settle more than sawdust or wood shavings). Typically, volume reduces by about 1/3 during this time.

What experiences can you share about keeping construction costs low?
The floor on smaller bins, up to about 7’ x 7’, can be slatted wood sleepers, with PVC aeration pipe in gravel. Larger bins should have a poured concrete floor, with formed air plenums, covered by 2” x 6” boards spaced for airflow.

Tarps can be used as covers on smaller aerated bins, instead of a roof, to reduce cost and rain. Small aerated bins can be left open. Tarps can also be used for covering the curing and storage compost area after removal from aerated bins instead of a constructed roof.

While work areas need to be an all-weather pad, but they do not necessarily have to be expensive poured concrete. Crushed red shale stone works well because if a little gets scooped up with compost, it does not have soil and is not visible.

Other operating or storage tips can you offer?
Once the 30-days of composting is complete in the aerated bins, the compost can be co-mingled and stockpiled in bulk for distribution over time. The compost stockpile area can be formed from delivered precast 2’ x 2’ x 6’ concrete staking blocks, or wood construction, on a all-weather loading base. Larger structures will need a roof, while smaller structures can be tarped.

Have a plan to spread the material on site, sell the compost, or properly remove and dispose of this finished material, which has great value as a horticultural crop soil amendment. The compost will take another year to break down into a humus type product. While equine and livestock managers need help with the process initially, it quickly becomes routine. Aerated bin composting and storage confines manure to one location on the farm and truly gives a nice product.

A Worthwhile Effort

How effective is composting in your aerated bins?
The composting process proceeds well even in cold weather. More traditional windrow or static pile compost methods by comparison may stall in cold winter temperatures.

I have monitored and charted temperatures in my aerated bins on many occasions. As the compost process begins, temperatures quickly climb over a period of about one week, rising to 150-160°F, as long as the moisture level is correct.

Temperatures remain elevated for approx. two more weeks during composting, then begin a slow cooling taper for a week or two. The composting is completed in about 30 days. The compost can be removed even while warm days after 30 days to a curing, storage, and distribution pile area to refill the bin.

If kiln dried wood shavings were used as animal bedding substrate, you need to wet the manure in the bins to initiate the composting process.

Was constructing your Aerated Compost Bins worth the effort?
Yes! Our grower sums up the benefits of on-farm composting in aerated bins as a simple, cost-effective and environmentally friendly manure management system.
Here’s the take away from today’s farm call:

• Bin design can accommodate many different farm situations. Two to four bins can be constructed, based on the number of animals and on the type and quantity of bedding.
• Bin systems require less space than traditional windrow composting.
• During the composting phase, the material is aerated from below, with air supplied by means of a small blower and PVC piping in the floor; turning-labor, equipment, and handling are reduced.
• USDA NRCS requires manure in the composting system to reach 130°F for a minimum for three days to be considered compost. Aerated bins handily exceed this standard.
• Aeration speeds up the composting rate, while controlling the pile temperature; destroying pathogens, parasites, and weed seeds. The composting may degrade animal vaccines, antibiotics, deworming products, and pesticides.
• Aerated Bin Composting mitigates nuisance problems from flies, odors, and rodents.
• The process takes 30 days, based on temperature readings. The material is removed from the bin and allowed to ‘rest’ or cure for another 30 days. At this point, the compost material makes a great Jersey Coastal Plain soil amendment blend.
• The process reduces the volume of original material by approximately one-third, converting waste to humus rich soil amendment, which is good for the environment and crops.
• On-farm Aerated Bin Composting reduces or eliminates off-site disposal costs.
• Aerated Bin Composting serves as an overall manure management plan from horse to end use for farms.