Influence of Fertilizers Applied to a Paddy−Upland Rotation on Characteristics of Soil Organic Carbon and Humic Acids

Abstract

The qualitative and quantitative characteristics of soil organic carbon (SOC) and related humic acids (HAs) extracted from the soils of field plots were investigated after 8 years of annual paddy (Oryza sativa L.) and upland maize (Zea mays L.) rotation with various fertilizations. Seven fertilization treatments were selected: Ck (no inputs); Chem (chemical fertilizer of NPK); Comp (swine compost); Comp + 33% of Chem N rate; Comp + 67% of Chem N rate; GM (legume green manure) + 33% of Chem N rate; and peat + 33% of Chem N rate. Organic and inorganic nitrogen inputs of six treatments were equivalent with respect of nitrogen content, but Comp, GM, and peat treatments were complemented with various amounts of inorganic N. After harvest of the eighth paddy crop, surface soil samples collected from the plots were subjected to soil characterizations and extraction of humic substances, which were used for chemical, spectroscopic (FTIR, 13C NMR, ESR, X-ray diffractometry), delta13C, and 14C dating analyses. The yields of HAs extracted from the seven treatments were significantly different. Treatment containing persistent organic compound such as the peat + 33% N treatment increased the humification process in topsoils and produced higher yield of HA. Spectroscopic analyses revealed that fertilization treatments changed the functional groups, alkyl C, crystalline characteristics, and delta13C ratios of HAs and turnover rate of SOC considerably. The SOC of the peat + 33% N treatment had the highest mean residence time of 3100 years. Various fertilizer treatments are correlated with turnover rate of SOC and related HAs, which are associated with concerned carbon sequestration as well as mitigation of CO2 emission in the soil environment.

Long-Term Effect of Different Fertilization and Cropping Systems on the Soil Antibiotic Resistome

“…Common agricultural practices like fertilization, irrigation, tillage and different cropping systems are known to or can be expected to affect both the introduced and natural soil resistome. This can be by selection for the antibiotic resistance trait, either by an antibiotic or another function of that trait (coselection), or by selection for other features of populations with the resistance trait being carried along incidentally . Manure application is the most likely practice to affect soil ARGs because it often carries large populations of ARG-carrying bacteria, is rich in available carbon for bacterial growth and in recent times may contain antibiotics, metals or other coselectants.…”

“…The latter has not been extensively investigated although one long-term study of fertilization practices on sulfonamide resistance gene showed that there is no significant difference between the NPK applied paddy soil and the wetland soil from a mountain site pond in South Korea . Applied fertilizer has different fates and effects in the dryland vs paddy soils due to their different water regimes, soil structure and bacterial composition, ,, which should result in different structures and dynamics of the intrinsic and the introduced resistome. However, there are no studies reported on this aspect.…”

Effects of long-term fertilization on soil humic acid composition and structure in Black Soil

“…Humic acid (HA) is an important component of soil humus, and its composition, structure and properties are directly related to soil fertility and crop yield [ 2 ]. The addition of organic materials increases the content of HA in soil and changed its chemical structure [ 3 – 4 ]. Galantini and Rosell [ 5 ] found that fertilized soil raises the contents of aliphatic and phenolic hydroxyl groups in HA compared with unfertilized soil.…”

Cropping systems modulate the rate and magnitude of soil microbial autotrophic CO2 fixation in soil

“…Paddy-upland rotation cropping systems differ from normal paddy rice and upland crop systems, where various water regimes are practiced in different crop growth seasons (Nishimura et al, 2008 ; Liu et al, 2010 ). During the submerged period of paddy rice cultivation, the anoxic conditions restrict the mineralization processes in soil, whereas the drainage of paddy fields for upland crop cultivation resulted in an oxic condition which enhances the decomposition processes within the soil (Chang Chien et al, 2006 ; Iqbal et al, 2009 ). As a result, physicochemical properties (e.g., SOC) are significantly altered in paddy-upland rotated systems when compared to paddy and upland soil traditional cultivation methods (Wang and Yang, 2003 ; Liu et al, 2010 ; Zhu et al, 2010 ).…”

“…During the submerged period of paddy rice cultivation, the anoxic conditions restrict the mineralization processes in soil, whereas the drainage of paddy fields for upland crop cultivation resulted in an oxic condition which enhances the decomposition processes within the soil (Chang Chien et al, 2006 ; Iqbal et al, 2009 ). As a result, physicochemical properties (e.g., SOC) are significantly altered in paddy-upland rotated systems when compared to paddy and upland soil traditional cultivation methods (Wang and Yang, 2003 ; Liu et al, 2010 ; Zhu et al, 2010 ). In this study, all soils were collected from the same climatic condition, and have the same origin and cultivation history.…”