By Bryan O’Hara
For many years we have been composting various agricultural and forest materials at Tobacco Road Farm to provide for the soil fertility in order to raise vegetable crops without the use of pesticides. This practice has been highly successful though it has required more refinement as the environment continues to deteriorate and the soil’s need for rebalancing becomes increasingly important.
The composting system is the mouth and stomach of the farm system and prepares the nutritive materials for absorption into the soil. How we choose the appropriate materials to feed into this system, along with an examination of mixing, piling and application of this material, is the focus of this article.
Let us set the stage of how and why this compost is utilized on our farm. At Tobacco Road Farm in Lebanon, Connecticut, we focus on intensive vegetable production with 3 acres in crops. The vegetable fields produce tremendous volumes of crops year-round. The soils are typical of the Northeast with a sandy acidic nature. The impact of pollution and climate manipulations on our soils is tremendous. The forest surrounding the farm is in a rapid state of decline. There are die-offs of trees and vastly reduced numbers of insects, bats, frogs, snakes and birds.
The variety of pest insects and diseases of vegetable crops moving into the region continues to increase and is a reflection of the environmental conditions. It has been very useful to re-examine compost and its utilization through a holistic eye that can see these changes and adjust the compost system accordingly. This is similar to the way humans have had to adjust their diets in this modern age of illness.
We utilize many techniques to deal with these difficulties, including no-till (Acres U.S.A., October 2016), Indigenous Microorganism cultures (Acres U.S.A., September 2017), foliar feeding, side dressings and cover crops as well as composting.
The no-till nature of the growing system influences compost production dramatically. Since the compost will only be applied to the surface of the soil and not turned into it, it simplifies its making greatly by allowing for more bulking with carbon-rich materials like wood chips. This allows for more air infiltration and thus less turning. The top-dressing of compost also allows for a less-decomposed compost to be applied, which is of great benefit to the hungry soil life. Let’s have a look at the materials and the process.
For raw materials we blend relatively large amounts of carbonaceous wood chip, leaf and straw with nitrogen-rich cattle manure and vegetable wastes.
We maintain separate piles of all these ingredients on the farm and then blend them into compost windrows.
The wood chips come from our surrounding forest and is primarily deciduous in nature. Often the chips are from roadside clearing and contain the small, more nutrient-rich branches and also possibly leaf.
The chips are available from various sources that manage to pile this material directly from roadside clearing trucks or land clearing companies. The material is generally free, but transportation adds cost.
Wood chips are considered one of the cleanest materials in commercial composting as the trees generally receive little to no pesticide applications, and there is little foreign matter mixed in. Wood chips are the primary ingredient in our compost.
Leaves are also incorporated into the compost at a relatively high volume. Leaves are generally collected in the fall so ample space is provided to bring in this harvest. Landscapers are our choice of providers here, where we have a personal relationship and can secure high quality. Again the material is essentially free, however we pay to have the materials delivered. Municipalities also collect large volumes of leaves and are often looking to give them away, however they contain a fair bit of plastic debris that must be picked out. Leaves also offer less risk of chemical contamination, however caution should be applied if lawn grasses are mixed in to any great degree.
Straw is another source of high-carbon material and provides a diversity of ingredient to our mix. The potential for herbicide contamination in straw is substantial so straw is secured from local producers whose practices are appropriate or from large commercial organic farms. The danger of “persistent” herbicide residues is said to be the most challenging problem in commercial composting. The chemicals do not readily break down during composting and can damage vegetable crops.
This group of herbicides is used in the production of small grains and hay.
When necessary, we purchase 1,000-pound square bales from organic farms in the grain growing regions of Maine. Since the straw is purchased and trucking is often paid for as well, it is our most expensive compost ingredient and thus is used to a lesser degree.
Straw is seldom totally free of the seed if the grain was harvested with a combine, however some rye straw is purchased from a local farmer who harvests before the seed heads are formed, yielding a seed-free straw. This rye straw is long-stemmed and is often run through a bale chopper for use as mulch (this helps with decomposition as well).
When used in composting, the straw, which has been run through a combine tends to be shorter in length and is generally not run through the chopper; instead the bales with grain seed in them are roughly laid out to allow rain to sprout the seed. Then the straw can be utilized either as mulch or put into the compost, as the process of moving the straw after grain germination effectively kills the sprouted grain.
Tobacco Road Compost Recipe
40% wood chip
20% leaf and/or straw
30% cattle manure mixture
10% vegetable scrap mixture
Mineral Additions at Assembly
(to about 30 yards-plus of base ingredients)
5-10% quarry dust or clay subsoil
100 lb gypsum
150 lb calcium silicate (wollastonite)
25 lb hydrated lime
250 lb talc (magnesium silicate)
100-200 lb soft rock phosphate
(1-3 months later)
250 lb talc
100-200 lb soft rock phosphate
5-10 lb elemental sulfur (depending on pH of pile)
50 lb agricultural sea salt (Sea-90)
40 lb manganese sulfate
5-10 lb sodium molybdate
5 lb zinc sulfate
5 lb copper sulfate
1 lb sodium borate
2 oz. cobalt sulfate
And a splash of selenium feed supplement[/box]
Grass-Fed Cattle Manure
The primary nitrogen-rich material we utilize is grass-fed cattle manure. This material is from a nearby herd that is fed the farm’s hay on in-field concrete feed pads during the cooler months. This allows for easy collection of the manure and spent hay, especially with a few well-placed large concrete blocks for the loader to push against.
Since the hay is produced on the farm, the potential herbicide contamination is low, and the cattle eating grass in a natural environment are very healthy and require very little to no veterinarian intervention.
The mixed hay and cattle manure piles on the pads often are heating and composting at a high temperature (above 150°F) before we even begin to haul them for further composting at the farm. Cattle manure has a long tradition of being the manure of choice for vegetable crop production. It composts very well, adds an appropriate biology to the composting process and is the easiest manure to use for high-quality compost. We have also used manures from various other animals, including our own poultry flock as well as fish processing waste.
With all of these materials, contaminants always need to be seriously considered including de-wormers, antibiotics and feeds grown using persistent herbicides. That being said, nothing has produced as beneficial a compost for us as the cattle manure. The manure is piled on a wood chip base, when brought to the farm, and covered with a high-carbon material like leaf/wood chip/straw to await further assembly.
The other primary nitrogen-rich material utilized in the compost is vegetable scrap backhauled from our co-op grocer and restaurant accounts, combined with the farm and household wastes. This material provides a lot of feed for the poultry, but generally does need to be covered with the high-carbon materials to keep it from attracting flies and varmints and to begin the composting process.
It is surprising how much carbon materials need to be mixed with this vegetable scrap in order for it to properly compost. This pile is also preheating to a high temperature before being mixed into the fully assembled compost windrows.
It is much harder to make high-quality compost using just this material as the nitrogen source, but it works well when combined with cattle manure.
Minerals are the final raw ingredient. Often we utilize a ground rock from our local quarries such as traprock (basalt) or sometimes granite. This material is the end result of rock crushing and is very inexpensive at $3 to $5 a ton plus trucking. It is high in silica, a much-needed nutrient for us, and provides a clay-like material to provide a base for the compost to build aggregates upon and for clay-humic complexes to form.
Clay subsoil from on-farm digging projects is also often incorporated. Other ground minerals of clay nature that are used in the compost are talc (magnesium silicate), wollastonite (calcium metasilicate) and rock phosphate (calcium phosphate).
Additional materials used include: gypsum (calcium sulfate), zinc sulfate, manganese sulfate, copper sulfate and cobalt sulfate along with sodium borate, sodium molybdate, sodium selenate and hydrated lime.
Seawater or liquified sea salt is also incorporated. Many of these materials and salts are utilized in very small quantities, and the formula is based upon tissue and soil laboratory testing, crop response in the field and other guidance. They are therefore somewhat unique to our fields’ conditions.
Although the formula on page 20 is specific to our farm, I’ve provided it to give you an idea of materials and amounts that have proven useful for our situation.
Composting Area, Method
The composting area is built up with a base of stone and processed gravel to allow for drainage and tractor traffic, though piles on top of topsoil may allow for even better soil microbe/compost pile interactions. The area has solid, easy access for truck deliveries of material. This always makes the truckers happy: an important component.
The raw materials are piled separately, except as noted when some carbon materials are premixed into the nitrogen-rich materials for preservation of quality. Generally all the materials described are present, however sometimes piles are assembled with more or less, or the complete absence, of a material.
The basic formula is something like 40 percent wood chip, 20 percent leaf and/or straw, 30 percent cattle manure and 10 percent vegetable scrap. On top of this is the quarry dust or subsoil and other minerals and clays up to a volume of about 10 percent, which of course gives 110 percent, but the point is that the loader takes four buckets of wood chip to two buckets of leaf to three buckets of cattle manure, etc.
The cattle manure and vegetable scrap also contain fair amounts of the more carbon-rich materials so overall the pile is quite high in carbon and moderate in nitrogen. This allows the pile to heat to a generally lower composting temperature of about 120°F, which favors a more fungal-rich compost, which is what we’re after due to our soil conditions.
The high volume of wood chip allows bulking of the pile that gives the ability of the pile to breathe and allows for adequate air infiltration, greatly reducing the need for turning, which is of benefit to fungal organisms.
The piles are built into windrows of about 15 feet wide and 6 feet high with varying lengths. Upon initial construction, wood chip is piled first at the base about a foot thick, then the other materials are piled atop this with as much mixing with the tractor bucket as can be done quickly and efficiently.
As the tractor is assembling, the minerals — talc, hydrated lime and wollastonite — are sprayed onto the pile. This liquefying and spraying requires two people as some of the minerals do not go into solution, and they must be constantly agitated in a large stock tank of water by hand.
A heavy-duty sump pump then moves the slurry to another person with a hose who is spraying down the pile.
This gives us a better mix into the pile and greatly cuts down on our exposure to the aggravating silica dusts and hydrated lime. The gypsum and rock phosphate are often applied dry as they are less dusty, and this helps cut down the amount of minerals that need to be agitated.
The pile is then covered with a bit of straw to provide a “skin,” and the biodynamic compost preparations are applied; they are a blessing for the pile. The pile is allowed to sit for a period of a month or more before it is turned. This is generally the only turning the pile receives and is an opportunity to further mix the materials as well as apply additional minerals.
The piles are turned using a loader tractor, and basically the windrows are moved sideways. At turning, additional talc and clay minerals are supplied, however a second stock tank is now mixed with the various salts that go into solution, and that is sprayed on as well.
The vast majority of mineral additions to our fields happen through the compost. This allows for digestion of these minerals into more accessible and biological forms and is very useful for the more difficult-to-access minerals like silicates.
It is also very useful for buffering the potential damage that the use of the soluble minerals could inflict upon the soil biology if applied directly.
The introduction of most of the materials, especially the soluble salts,later in the composting process seems best in terms of timing as it allows the process to be well underway before introduction of materials that could reduce biological activity. Also the piles are better prepared to buffer and hold these soluble nutrients at this time.
The addition of these mineral materials goes a long way toward increasing the soil’s fertility. Our soils have been damaged by past agricultural activities and the impact of various pollution sources. The pollution impact, combined with the use of various agricultural chemicals, has resulted in organic materials that are highly imbalanced, so as feedstocks for the composting system they are lacking in various mineral nutrients and excessive in others. In other words, it is difficult to take materials from a dying forest or from damaged agricultural soils and turn them into high-quality compost without some adjustment.
The knowledge of how to adjust the compost recipe comes from a variety of sources, including trialing various composts for their impact on soil and crop health, utilizing long-term soil and tissue testing to see mineral nutrient trends, biodynamic principles and spiritual guidance.
The temperature of the piles is monitored, and generally the hot cattle manure and vegetable scrap materials start to cool to about 120°F when they are incorporated in the windrows with such large volumes of carbon. This is the condition that we are seeking as our crops respond well to the more fungal-rich compost, which these lower temperatures encourage.
The compost is considered ready for use when the temperatures have dropped close to ambient and the nitrogen-rich manure and vegetable scrap has decomposed. Often there are still partially decomposed carbon materials left; this is ideal as with surface application these less-decomposed materials provide excellent food for in-field soil biology. So the compost at this stage resembles a mulch/compost mixture.
Moisture & Air
Other conditions to monitor as the piles progress include moisture and air. When there is more air there is less water, and vice versa. Generally in our environment in the Northeast there is sufficient rain for composting, so rarely do we have to add moisture, however the piles do need coverage during periods of excessive rain, often in the cooler months.
To cover these piles we use large, black plastic tarps, often silage-style tarps that have previously been used to cover straw or for field occultation. These used tarps have a few holes, which are helpful in allowing the piles to breathe while shedding the vast majority of rain.
Proper air penetration into the pile is provided by the coarse nature of the materials composted, along with moisture control and proper sizing of the piles.
Insufficient air will lead to anaerobic conditions which results in off-smelling compost with a black color similar to swamp muck. If this occurs we recycle this material into a new compost pile.
The compost is spread when the piles have significantly cooled using a loader tractor to fill various spreading equipment, such as a manure spreader, dump truck or a line of wheelbarrels. The dump truck and manure spreader fit to the bedding system.
The compost is spread on the surface of no-till soil, making it important to keep the material from drying out, so after the compost is spread the beds are seeded or planted, mulched and irrigated pretty much immediately. This preserves the biology present in the compost and provides an environment appropriate for plant feeder roots to penetrate the compost. Compost is spread before most, but not all crops, at a rate of about 30 tons per acre, or a wheelbarrel-full to 150 sq. feet.
The compost described here is utilized pre-plant and is meant for broadfield application to assist in soil remineralization and balance as well as to provide a food source for the very hungry soil biology in our fields. We also produce specific composts for other uses on the farm including specific blends for side-dressing vegetables at various growth periods, potting soil and vermicomposting.
Liquid compost extracts from the vermicomposting system are utilized in the liquid side-dress fertilization to help buffer salts. These specific compost recipes will have to await future articles.
When discussing composting with other farmers, one recent concern has been phosphorus levels. Various laws and regulations have limited the application of phosphorus-containing materials including compost in the name of water quality. This kind of broad sweeping regulation defies common sense, agricultural tradition and experience; stands on weak science; and is unlikely to help water quality when the greater picture is considered.
However, phosphorus can be excessive in composts if they are not properly blended. Phosphorus levels are highly related to the grain ration in animal feeds, so usually the manures of these grain-fed animals are responsible for elevated phosphorus levels in compost.
Without manure from grain-fed animals we have seen the phosphorus levels on the Mehlich III soil test drop when applying 30-plus tons of compost per acre per year.
If you are interested in a more scientific evaluation of phosphorus level and plant availability, saturated paste soil tests and tissue analysis will probably give a more accurate assessment than the strong acid Mehlich III extract.
I have seen many lab results from various farms in the region showing what are now considered “high” levels of phosphorus on the Mehlich III that have low to very low levels of phosphorus on the weaker LaMotte and saturated paste soil tests as well as tissue analysis. These soils may well benefit greatly from phosphorus-containing compost application.
Compost is of course the very heart, backbone, and shall we say, digestive tract of the organic system of agriculture.
Most soils I’ve observed on vegetable fields in the Northeast region would most likely benefit to a great extent from the application of high-quality farm-made compost.
The benefits of the biological stimulant nature of compost are quite significant in terms of yield and quality, especially when combined with materials that aid in the mineral nutrient balance of the soil.
Compost can indeed imbalance a soil if the materials utilized are in severe imbalance, so guidance here may be appropriate. However, often the best way to learn these things is by doing: make the compost, trial it, evaluate and learn from error and success.