|Virginia Tech researchers study the effects of compost on experiment station vegetable plots to improve soil quality, including water-holding capacity and infiltration. |
Photo by Greg Evanylo
Some farmers, particularly organic producers, have long applied manure and compost to meet their fertility needs. However, most non-organic vegetable producers rely on the quicker fix of annual applications of commercial fertilizer. SARE-funded researchers in Virginia tested compost on non-organic vegetable farms to demonstrate its ability to enhance soil quality, including water-holding capacity, bulk density, infiltration, organic matter and plant-available nutrients.
“Water stress is the most critical environmental factor limiting crop production in the southeastern United States,” said Greg Evanylo, professor of crops and soil environmental sciences at Virginia Tech. “After a few drought years, farmers tend to better understand the importance of soil quality.”
Evanylo determined that applying compost (made from three parts yard waste to one part poultry litter) at rates designed to meet vegetable nitrogen needs reduced soil bulk density and compaction, and increased water infiltration.
Compost is relatively expensive. Yet, rising commercial fertilizer costs and nutrient management regulations that prevent confined livestock operators from land-spreading manure on high-phosphorus soils might prompt more producers to begin composting, Evanylo said.
On a previous study, Evanylo found that compost applications at high rates improved yields and water-holding capacity in sandy soils. “When you add cover crops or lots of organic matter, it maintains the structure at the soil surface, preventing the beating-down effect of raindrops that break up the soil,” he said. “It allows water to infiltrate and increases storage.”
You don’t have to use compost, however. Consider applying uncomposted organic material directly to the soil and also using cover crops. Bob Muth, who grows vegetables and hay on 52 acres in Williamstown, N.J., augments his soil organic matter by using cover crops and spreading the leaves collected by local municipalities on some of his fields each autumn. Over the years, he has vastly improved the soil’s infiltration, a must on his gravelly sandy loam that includes 15 percent clay and a tendency to crust.
Typically, Muth covers the ground with up to six inches of leaves, or 20 tons per acre. The following spring, he works in the decomposing leaves. He also plants a variety of cover crops, including sudangrass, a quick-growing high-mass summer cover that breaks up compacted soil. His fields test as high as 5 percent organic matter, unheard of for the mineral soils of southern New Jersey.