David Granatstein, Washington State University, recommends growers consider the following before using a mulch.
• What is the volume needed? Using a 3-foot strip under the vine, an inch deep would equal 44 cubic yards per acre.
• What is the bulk density?
• What are you bringing in? Run a chemical analysis on the dry material.
• How much nitrogen is released and when is it released?
• What are the long-term effects?
• Are there contaminants, weed seeds, pathogens, or odors? Chicken manures can contain arsenic.
• What is the material's longevity?
• What is the impact on soil pH and soil electrical conductivity? Mulches that add high salts can kill trees and vines.
• What is the cost for transporting and spreading? Mulches are bulky and can be expensive to spread. WSU estimated that it costs around $900 per acre to buy, shuttle, and spread mulch in an orchard.