PERSPECTIVE

Compost Science & Utilization, (2004), Vol. 12, No. 4, 295

Protecting Crops And Recycling Nutrients

THE FIRST THREE PAPERS in this issue of Compost Science & Utilization specifically address the role of compost as a nonchemical alternative to commercial pesticides and its significant impact on managing nutrients in feedstocks. Researchers from around the world provide CS&U readers with authoritative results and analyses that add to our understanding of the compost process.

As Patricia Millner and her colleagues at the Agricultural Research Laboratory in Beltsville, Maryland explain in the first paper, the soil fumigant - methyl bromide (MeBr) - has been commonly used by growers to eliminate root disease fungi, nematodes and weeds in high-value crops such as strawberries and tomatoes. But because of its role in depleting stratospheric ozone, this soil fumigant will no longer be allowed, first in developed countries as of January 1, 2005 and eventually worldwide by 2015. Amending soils with compost is recommended as a replacement for MeBr. “During the past 20 years, research on biological control and natural suppression of soil borne plant pathogens has included effects from the use of complex organic substrates, like compost, many of which have been shown to be effective in protecting plant health,” the scientists observe on p. 298 of their report, Suppression of Strawberry Root Disease with Animal Manure Composts. Incorporating compost into strawberry plantings provides a needed “window of opportunity” to increase microbial balance and biological buffering in soils. A single high rate compost application promotes a rapid increase in soil organic matter and biological activity (enzymes, respiration, soil microbial population) associated with suppressive conditions.
At the Ohio Agricultural Research and Development Center in Wooster, Fred Michel, Harold Keener and their colleagues provide greater clarity on how farmers can use amendments like sawdust and straw to reduce composting costs. Moisture management proved critical in reducing manure weight during composting. “Through composting,” they point out, “farmers can reduce volume and weights of material to be hauled by 50 to 80 percent.” Many farmers haul manures up to 10 km (six miles) from their farm to avoid overapplying nutrients and reduce water pollution.
Another study at the Ohio Agricultural R&D Center - which begins on p. 356 - reports results of a “modeling rate” design that would cut energy use and costs in composting such residuals as paper mill sludge and broiler litter by as much as two-thirds. “Results showed operating the system at 60°C would require 31 percent of the fan energy cost compared to, operating at 50°C. Regression analysis of cumulative CO2 as a function of variables yielded results similar to those based on maximum CO2 generation rates,” conclude the Ohio State University team.
Based on their work at the Louisiana State University Agricultural Center, Gary Breitenbeck and David Schellinger (p. 365) explain how loss of mass and volume during composting of various feedstocks is critical for facility design and operations. They present equations for calculating reductions in mass, volume and organic carbon. Their findings - along with the other papers presented in the following pages - serve to fulfill the need for data that optimize facility performance.

Copyright 2007, The JG Press, Inc.