Assessing the Value of Separated Dairy Solids for Agronomic and Horticultural Use.

With growing consumer interest in environmentally-responsible practices and the climbing costs of commercial fertilizer, the use of organic amendments to fulfill nutrient requirements and improve soil quality has garnered attention from farmers and Green Industry professionals alike. New technologies that separate organic solids from dairy manures offer dairy farmers the opportunity to develop value-added organic products that can fit into two markets: a fresh product for agronomic crops or a composted soil amendment for turf and home horticulture or specialty crops. Few studies, however, have addressed the effects of the use of separated dairy manure solids in field crop production or characterized the properties of composts produced from dairy solids. A greenhouse study was initiated to investigate the effects of raw separated manure solids produced at the University of Delaware dairy farm on corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and alfalfa (Medicago sativa L.) growth. Six rates of dairy solids ranging from 0 to 180 Mg ha^-1 were incorporated into a Sassafras sandy loam soil. Effects of dairy solids on seedling emergence, plant growth, elemental uptake, nitrogen availability, soil phosphorous forms and solubility, and soil physical properties (particularly water relations) relative to inorganic fertilizer will be reported. A second goal is to quantify the effects of various composting practices on the physical and chemical properties of dairy solid composts that affect their suitability for use in horticultural settings, such as turf, and the production of high value vegetable and specialty crops.