A key to handling sand-laden manure is to prevent the sand from entering the liquid containment structure or vegetative treatment system. Most dairies find it difficult to remove sand from a containment structure because the material settles in different locations during agitation. Therefore, the key is to prevent the sand-laden manure from ever having to be agitated.
The minimum storage period is often based on cropping practices. The minimum recommended storage period is 60 days; however, some states require 180 days of storage. Contact your state regulatory agency for the required storage period. Dairies growing small grain may have land available during the summer months for manure application, and 120 days of storage may be acceptable. Manure generally is spread during periods prior to tillage operations.
The simplest method of retaining sand is to construct a basin 4 to 6 feet deep that allows as much moisture as possible to weep away from the manure. The basin has concrete perimeter walls (some dairies have a weep gate in a section of the wall for access) and a floor in order to contain the sand-laden manure. This material tends to spread and in wet climates may never stack more than 12 to 18 inches deep unless it is contained.
The basin capacity is based on 1.5 cubic feet (cu.ft.) of sand-laden manure per cow per day. For example, a 100-cow dairy with 100 days storage would require a basin with a minimum capacity of 15,000 cu.ft. (1.5 cu.ft./cow/day x 100 cows x 100 days). For a basin that is 4 feet deep and 40 feet wide, the required length is 94 feet. One field study shows that a dairy will spend about 30 minutes per cow per year to load, transport, and spread the manure on a field. The manure in the basin will have a moisture content of 75 to 82% (wet basis) and a nutrient value of 10 pounds of total nitrogen and 4 pounds of phosphate per ton.
