April 21, 2011 | General

Home-Grown Compost Boosts Organic Vegetable Production

BioCycle April 2011, Vol. 52, No. 4, p. 28
Pennsylvania vegetable farmer cultivates fertility and disease suppression – with a little help from his worms.
Annie Hasz

IF the success of organic farmers can be measured by how effectively they keep valuable nutrients recycling in the system rather than relying on costly outside inputs, then Spiral Path Farm owner Mike Brownback is indeed a master at his craft. His main fertility applications are compost made largely from his cover crop biomass, vegetable waste and straw or what he calls chop, and his own foliar spray. Mesophilic microorganisms begin to decompose the waste and generate heat in Brownback’s homemade compost drum, aerates and accelerates decomposition. When the compost is sufficiently broken down, it is fed to thousands of red wiggler worms. The extract from these worm castings is the foundation for Brownback’s foliar spray, which is USDA National Organic Program (NOP) compliant.
Of Spiral Path’s 188 acres in Perry County, Pennsylvania, 80 are in vegetable production. Spiral Path is a Community Supported Agriculture farm (CSA) and in the 2010 season about 2,400 members got vegetables weekly. The soil must be fertile to attain these high yields and support double-cropping. In the early years at Spiral Path, Brownback worked to create this fertility by applying one tractor-trailer load of mushroom compost to each acre annually.
But in the early 1990s, a convergence of three conversations inspired him to make drastic changes to his fertility program. An extension agent warned that most of the nutrients in his heavy application of mushroom compost would simply leach away unused. Soon after at a conference, he learned that successful vegetable farmers Anne and Eric Nordell of Trout Run, Pennsylvania, never exceed a very light application rate of 1,000 pounds/acre of composted horse manure on their fields. Finally, Brownback met a hydroponic grower who credited his own production success to a liquefied vermiculture product. Meanwhile back at Spiral Path, Brownback was faced with the produce farmer’s perennial dilemma of unmarketable vegetables turning into waste. He began to experiment with homegrown fertility and worms.

Today, Spiral Path makes about 10 tons/month of vermicompost. The process begins in the 10,000-gallon homemade drum. Brownback and his crew mounted the drum onto two tractor-trailer axles. The drum is turned by a 2-horsepower engine four times a day.
The drum is loaded with a straw-to-vegetable waste ratio of 25:1 to 40:1. Other wastes, including paper products, also break down readily in the drum. The microbial activity and the aeration produced by turning the drum decompose the waste over two to four weeks. Clay is added to control the production of ammonia. Sometimes the contents of the drum are inoculated with finished worm castings.
The unfinished compost unloaded from the drum is formed into a windrow. Brownback adds clay and turns the mixture again until it is ready to feed to the red wiggler worms. Two inches of unfinished compost a week is given to the surface-feeding worms in two 32-foot by 6-foot by 3-foot worm beds. Brownback ensures the worms have plenty of mature compost substrate to moderate the addition of fresh compost, which may still be chemically “hot.”
Worm beds are regularly watered because red wigglers thrive in media with a moisture content between 70 percent and 90 percent. The beds are each equipped with a wire floor and a scraper attached to a winch. Vermicastings are collected below the wire floor and extracted to be mixed with other ingredients and foliar sprayed, or extracted in a greenhouse unit and used in fertigation (fertilizing via irrigation). The homebuilt extractor liquefies the worm castings using a regenerative pump that forces a high volume of air into the system. The liquefied extract is filtered and pumped into a 300-gallon sprayer. The vermicastings comprise the compost element in Spiral Path’s potting soil recipe, which also includes vermiculite, perlite and peat.
After three seasons of testing, Brownback reports that he is “satisfied that he can maintain fertility with this system.” If a soil test shows that elements such as calcium, potash or magnesium are deficient they are applied as minerals, but all nitrogen requirements and the health of soil microbe populations is completely derived from cover crops and the vermiculture extract. Brownback has seen an increase in crop resiliency at Spiral Path in the face of disease since he instituted his vermiculture-based fertility program. He noted that the farm was visited by late blight in 2009 but that the crops were not devastated by it. With the new fertility program, weeds are much more manageable and crops and yields continue to be healthy, adds Brownback.
Annie Hasz tends the soil at Taproot Farm in Shoemakersville, Pennsylvania. The article is based on a workshop presentation given by Mike Brownback of Spiral Path at the 2011 Pennsylvania Association for Sustainable Agriculture’s 20th annual Farming for the Future conference, as well as follow-up interviews.

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