Normally, irrigation and rain water will sufficiently leach well-drained soils to prevent damaging salt accumulations. However, one should be cautious with poorly drained soils, soils with existing salinity problems, or unusually high application rates, especially when concentrated near young plants. Zinc deficiency can be induced or increased with repeated high rates of manure, especially on sandy soils. Moderate or infrequent applications do not normally present a zinc problem. However, growers should be aware of the potential problem, especially with soils and varieties or crops of known susceptibility to zinc deficiency.
Manure is also helpful in improving soil fertility in cut areas from land leveling.
Nutrient content and rate of availability varies widely, depending mostly on manure source, handling methods, and water content. Fresh manure which includes both liquid and solid fractions with the least handling and then work in immediately after spreading will retain the most nitrogen. A laboratory analysis of the manure for nitrogen content is useful. An accurate sample of the manure requires a composite of many samples throughout the pile or lagoon. Generally, poultry manure is highest in nitrogen content, followed by hog, steer, sheep, dairy, and horse manure.