**2. Compost process and status in China**

Traditionally, farmers in China were mainly depending on organic fertilizers, for example, animal manures and agricultural residuals. In 1950s, farmers also began to apply some of chemical fertilizers (**Figure 1**). In 1980s, the application of chemical fertilizers and organic fertilizers had a very similar percentage. However, the application of chemical fertilizers in 2010 was over 90%. As a result, soil acidification is a major problem in soils of intensive Chinese agricultural systems. Two nationwide surveys showed that soil pH declined significantly (*P* < 0.001) from the 1980s to the 2000s in the major Chinese crop-production areas. [7] Therefore, the replacement of chemical fertilizers by organic fertilizers in a certain percentage is urgent.

During the last decade's development of composting in China, numerous large-scale animal farms with more than 10,000 pigs or 5000 cattle have been established. As a result, a large amount of animal manure is produced, which is a major pollutant if untreated [8]. On the other hand, this is also a perfect resource of organic fertilizers. For example, more than 100 factories produce over 5000 tons of commercial organic fertilizers each year in Jiangsu Province, China (**Figure 2**). Correspondingly, the Jiangsu government now subsidizes the composting factories

**Figure 1.** Percentage of fertilizers used in China from 1950 to 2005.

**1. Introduction**

2 Organic Fertilizers - From Basic Concepts to Applied Outcomes

materials of the latter.

improvement. [4–6]

**2. Compost process and status in China**

are introduced.

Composting is an inexpensive, efficient, and sustainable treatment for solid wastes. In China, the composting industry has been growing rapidly, owing to a boom in the animal industry over the past decades. Because an immature compost applied to soil results in seed germina‐ tion inhibition, root destruction, and a decrease in the O2 concentration and redox potential [1, 2],assessingorganicfertilizermaturityiscritical.Bytheway,amaindifferencebetweencommon composts and commercial organic fertilizers is the complexity and unpredictability of the raw

In recent decades, livestock numbers have increased dramatically in China. The quantity of manure generated by China's livestock has increased significantly as a result of the rapid increases in livestock numbers. The quantity increased by at least fourfold between 1980 and 2005, to an annual estimated total of 3060 million tons (Mt, fresh weight of manure) in 2005. [3] It was estimated that manure generation in 2010 was ca. 2800 Mt (fresh weight). [3] In addition, organic fertilizer amendment has been shown to be an effective way of increasing soil organic matter (SOM) content and reducing environmental pollution. However, the mechanism of storage of SOM remains largely unknown. Recently, some investigators have shown that organic fertilizer amendments could enhance the production of highly reactive short-range ordered (SRO) minerals, which further benefit for SOM storage and soil fertility

In this chapter, compost process and status, novel spectroscopy techniques in assessing compost maturity, and improvement of soil fertility by organic fertilizer amendments in China

Traditionally, farmers in China were mainly depending on organic fertilizers, for example, animal manures and agricultural residuals. In 1950s, farmers also began to apply some of chemical fertilizers (**Figure 1**). In 1980s, the application of chemical fertilizers and organic fertilizers had a very similar percentage. However, the application of chemical fertilizers in 2010 was over 90%. As a result, soil acidification is a major problem in soils of intensive Chinese agricultural systems. Two nationwide surveys showed that soil pH declined significantly (*P* < 0.001) from the 1980s to the 2000s in the major Chinese crop-production areas. [7] Therefore, the replacement of chemical fertilizers by organic fertilizers in a certain percentage is urgent.

During the last decade's development of composting in China, numerous large-scale animal farms with more than 10,000 pigs or 5000 cattle have been established. As a result, a large amount of animal manure is produced, which is a major pollutant if untreated [8]. On the other hand, this is also a perfect resource of organic fertilizers. For example, more than 100 factories produce over 5000 tons of commercial organic fertilizers each year in Jiangsu Province, China (**Figure 2**). Correspondingly, the Jiangsu government now subsidizes the composting factories

with 200 RMB per ton. As a result, the price of commercial organic fertilizers has decreased from 550 to 350 RMB. Therefore, the farmers are pleased to replace chemical fertilizers with commercial organic fertilizers. Presently, the total amount of commercial organic fertilizers produced by subsidized composting facilities is more than 2 million tons per year in Jiangsu Province, China (**Figure 2**). Thereof, the government of Jiangsu Province plays a critical role in promoting the production and application of organic fertilizers by the farmers.

**Figure 2.** Summary of factory locations to produce commercial organic fertilizers in Jiangsu Province, China.

**Figure 3.** Trough composting system (a) and windrow composting system (b) in China.

In China, trough composting system and windrow composting system are the main compost‐ ing processes, with windrow composting system being more popular in Jiangsu Province (**Figure 3**). Windrow composting consists of placing the mixture of raw materials in long narrow piles that are agitated or turned on a regular basis. The turning mixes the materials during composting and enhances passive aeration. Generally, the heights of windrows are in a range of 90 to 180 cm. Correspondingly, the width of them varies in a range of 100 to 300 cm. In general, the size, shape, and spacing of the windrows are determined by the turning equipment. During aeration, the rate of air exchange depends on the porosity of the windrow. Therefore, the size of a windrow is determined by its porosity.
