Compost is not hard to make on the farm once the basics of composting are understood, says Dr. Lynne Carpenter-Boggs.
Composting is simply decomposition that happens en masse, said Carpenter-Boggs, coordinator of Washington State University’s Biologically Intensive Agriculture and Organic Farming program. The cycle of mineralization and immobilization repeats itself during composting, she added.
Heat is one of the most important ingredients when composting. "You need to reach 130°F inside the compost pile to kill weed seeds and pathogens," she said during a recent Washington wine grape convention.
Single-cell bacteria—the compost workers—can double in number in less than an hour, she noted. Other organisms involved in composting include actinomycetes, which are the white strands found under the surface, and fungi. When the decomposing activity drops off, the compost enters the curing phase.
Compost material will differ depending on the amount of time it spends in active versus curing time. Sets of microorganisms work at different temperatures, Carpenter-Boggs explained.
"Composting is an excellent way to recycle organic wastes," she said, noting that Washington and other states are interested in reducing green waste. Other benefits of composting include improving the fertilizer value of the material and stabilizing nutrients. Composting can reduce the chance of "burning"crops with too much nitrogen or leaching of nitrogen from applied material. Compost can also neutralize soil pH and improve soil structure and tilth. Compost teas or extracts can be made from compost. Low-grade compost can be useful as a surface mulch.
"Generally, you have to make a blend of materials to achieve the right carbon-to-nitrogen ratio," she said, adding that grape pomace is composted by many, but can be hard to break down by itself due to the seeds. "A lot of materials will compost and break down, but they don’t all make good compost."
She advised those interested in making their own compost to start small and experiment with different mixtures and materials. For those growing crops organically, certain organic guidelines should be followed when making compost for organic-certified use.
To make your own compost, at least one cubic yard of material is needed. The following steps are needed for making compost:
• Carbon-to-nitrogen ratio should be in the range of 25 to 30 parts carbon: 1 part nitrogen (25:1). Soil laboratories can determine the carbon-to-nitrogen ratio. If the ratio is unknown, layer green and brown material alternately in your compost pile.
• Moisture of material must be 50 to 60 percent. If moisture content is unknown, use the "squeeze" test: squeeze a handful of material from inside the pile. If it drips, it’s too wet; if it crumbles, it’s too dry. The material should form a mass in your hand.
• Oxygen inside the compost pile is needed for microorganisms. Keep the pile aerated by turning a few times or using an air pump to inject oxygen.
• Temperature of the compost pile should reach 130°F for three weeks, during which time it should be turned at least twice. Organic compost must be held at 130°F for 15 days, with material turned five times. Some materials can get too hot in the compost pile and combust. If compost temperatures rise to 170°F, turn material to cool it down.