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Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/63047

#### **Abstract**

The word organic, applied to fertilizers, indicates that the nutrients are derived from the remains or by‐products of a once‐living organism. Farmers are continually searching for alternatives to synthetic inorganic fertilizers to alleviate the escalating production costs associated with the increasing costs of energy and fertilizers and the problems of soil and surface water deterioration associated with intensive use and release of inorganic fertilizers such as N and P fertilizers. One of the advantages of organic fertilizers is that they provide their nutrients especially the principal nu‐ trients (NPK) to growing plants over a long period of time in a slow release process. The soil has to be moist and warm enough to allow soil microorganisms to decom‐ pose and breakdown the complex forms of organic fertilizers. Generally, the applica‐ tion of organic amendments to agricultural soils makes good use of natural resources and reduces the need of synthetic inorganic fertilizers. Soil structure, nutrient composition, and microbiological activity of soil are usually increased following the application of organic amendments. This is because of the presence of sugars and amino acids as simple molecules in organic amendments that contribute to microbiological activity and fertility and elevated levels of enzymes secreted by soil microbes. To investigate the soil microbiological activity after the addition of soil amendments, three enzymes that control the C, N, and P cycles should be monitored in the plant rhizo‐ sphere zone, which is defined as the zone of increased microbial and enzyme activity where soil and root make contact. An increase of organic waste originated from different humans and productive activities is a continuous concern. Waste application (i.e., municipal sewage sludge, chicken manure, horse manure, and cow manure) to soil is proposed as a solution to disposal problem. This practice is popular in the agricultur‐ al fields because of the value of this waste as organic fertilizer. At KSU, numerous studies have been conducted on organic soil amendments and their impact on crop yield and quality, soil erosion and nutrient availability, soil enzymes activity, and bioremediation of heavy metals in organic amendments.

**Keywords:** sewage sludge, chicken manure, horse manure, yard waste, soil enzymes, antibiotics, heavy metals

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
