**1. Introduction**

Red soil, which is widespread throughout subtropical and tropical regions, is the most important grain production base in South China. Red soils are naturally poor in physical conditions and

© 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.

are also characterized by low pH, cation exchange capacity (CEC), and fertility. Red soil also has low concentrations of P in soil solution and results in frequent P deficiency of plants [1]. The improvements of soil fertility especially plant available P level, soil pH, soil structure, and waterholding capacity in the red soil region are always a major challenge. The application of chemical fertilizer alone, and that combined with organic fertilizers, such as crop residues and farm‐ yard manure, are two common approaches to improving soil quality for grain production [2– 5]. Rice (*Oryzasativa* L.) is the main cereal crop in the red soil region. Returning rice straw containing C, N, P, K and microelements to the soil (both used as a surface cover and incorpo‐ rated) has been extensively shown to increase organic matter and nutrient contents resulting in improved soil physical, chemical and biological characteristics. Crop residue is returning not only can increase crop yields, but it also can enhance soils' resistance to wind and water erosion [6, 7]. Animal manures, such as pig manure with ample N, P and K, are valuable resources to supply the needed plant nutrients and organic matters [2, 4, 5, 8, 9].

Therefore, rice straw and fresh pig manure are commonly used as organic amendments in the red soil region of China. When combined with chemical fertilizers, those organic amendments could effectively regulate soil physicochemical properties and soil fertility. Many researchers have proven that long-term application of organic-inorganic fertilizers significantly increased soil water supply capacity, promoted soil nutrient recycle and distribution, improved soil aggregate structure [2]. Therefore, in this chapter, the changes or fluctuations of soil acidity, soil organic matter, soil NPK fertility, and soil aggregate structure due to the combined application of chemical fertilizer and rice straw or pig manure in a long-term (1988–2009) experiment were summarized. Lessons learned can be used to improve nutrient management so that crop yields are optimized and the impact of food production on the environment is minimized.
