Manure is a valuable fertilizer for any farming operation and has been used for centuries to supply needed nutrients for crop growth.
Manure not only supplies many nutrients for crop production, including micronutrients, but is also a valuable source of organic matter. Increasing soil organic matter improves soil structure or tilth, increases the water-holding capacity of coarse-textured sandy soils, improves drainage in fine-textured clay soils, provides a source of slow release nutrients, reduces wind and water erosion, and promotes growth of earthworms and other beneficial soil organisms. Most vegetable crops return small amounts of crop residue to the soil, so manure, compost, and other organic amendments help maintain soil organic matter levels.
Proper use of manure is essential from both a production and environmental standpoint. Applying rates that are too low can lead to nutrient deficiency and low yields. On the other hand, too high a rate can lead to nitrate leaching, phosphorus runoff, accelerated eutrophication of lakes, and excessive vegetative growth of some crops. Thus, understanding how to manage manure is important for any farming operation with livestock that relies on manure as a major source of nutrients, as well as for vegetable producers who have access to an economical supply of manure, compost, or other organic nutrient sources. 
- Rosen, C. and Bierman, P. (2005), "Using Manure and Compost as Nutrient Sources for Vegetable Crops", Department of Soil, Water, and Climate, University of Minnesota