The relationship between soil WEOC distribution in the soil profile and water flows was indicated by Mertens et al. (2007) [55] and Junod et al. (2009) [56] on arable soils. But DOC contents in deep soil solutions in NFI paddies were always lower than sellectchem those in FI paddies (Figure 4). It indicated that downward moving of DOC was determined more by deep seepage volume than the DOC contents in surface soils. 4.2. Potential Environment ImpactsHigh WEOC and DOC contents in NFI soils are the consequence of the high microbial oxidative breakdown of soil organic matter and turnover of microbial biomass [2]. The high microbial activity in NFI soil will be accompanied with high soil respiration [57, 58], which led to greenhouse gas (CO2 and CH4) emission. The lower SOC contents in NFI surface soil also confirmed it.

Compared with FI paddies, less carbon was accumulated in deep soils (40�C60cm) and more SOC was lost in surface soils (0�C20cm) of NFI paddies (Figure 6), although the differences were mostly insignificant for one-year experiment in current research. If the NFI is applied to rice paddies in long-term, the effect on soil carbon pool and soil carbon output will be accumulated and get even significant. The reduced SOC content in NFI surface soils indicates that more carbon was released into the atmosphere from surface soil than in FI paddies. A study regarding the greenhouse gas emission from NFI paddies [47] reported that seasonal CH4 emission from NFI paddies was 1.17�C1.35gm?2, which was much lower than that (6.62�C7.20gm?2) from FI paddies.

Thus, we can deduce that more CO2 was released from NFI paddies than FI paddies because the aerobic condition favored carbon decomposition [45]. The reduced percolation in the NFI fields also led to lower DOC leaching loss than in FI fields that is helpful to reduce the risk of groundwater pollution. In addition, solubility of SOC concentration (especially DOC content) is also an important factor for the translocation of trace metals [11�C13] and organic compound pollutants [8�C10]. Thus, soil respiration rate, SOC fractions, and translocation of heavy metals and organic compounds should be studied to help illustrate the ecoenvironment effect of water saving irrigation on rice paddies.4.3.

Soil Fertility and SustainabilityGenerally, flooding condition in rice paddies frequently results in high SOC contents compared with the upland’s seasonal soil carbon accumulation, or results in long-term SOC continuous accumulation [59�C61]. As a result of enhanced decomposition Dacomitinib and mineralization of SOC in NFI surface soil, SOC in surface NFI soil decreased. Long-term application of NFI in rice fields might lead to more release of carbon from surface soil and consequently lead to degradation in the soil fertility and sustainability.