Plaza César, Senesi Nicola, García-Gil Juan C, Brunetti Gennaro, D'Orazio Valeria, Polo Alfredo
Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Científicas, Serrano 115 dpdo., 28006 Madrid, Spain.
J Agric Food Chem. 2002 Aug 14;50(17):4867-74. doi: 10.1021/jf020195p.
The effect of three annually consecutive additions of pig slurry at two rates (90 and 150 m3 x ha(-1) x year(-1) on soils and soil humic acids (HAs) was investigated in a field experiment under semiarid conditions. Soils and pig slurries were analyzed by standard methods. The HAs were isolated from soils and pig slurry by a conventional procedure based on alkaline extraction, acidic precipitation to pH 1, purification by repeated alkaline dissolutions and acidic precipitations, water washing, dialysis, and final freeze-drying. The HAs obtained were analyzed for elemental (C, H, N, S, and O) and acidic functional group (carboxylic and phenolic) composition, and by UV-vis, FT-IR, fluorescence, and ESR spectroscopies. With respect to the control soil, the pig slurry amended soils had greater pH and electrical conductivity, slightly larger total N content, and smaller values of C/N ratio. A decrease of total organic C was observed only in soils amended for 2 and 3 years at the higher slurry rate. With respect to control soil HA, pig slurry HA was characterized by larger contents of S- and N-containing groups, smaller acidic functional group and organic free radical contents, a prevalent aliphatic character, extended molecular heterogeneity, and smaller aromatic polycondensation and humification degrees. Amendment with pig slurry HA determines a number of modifications in soil HAs, including increase of C, S, and COOH contents, C/N ratios, and aliphaticity and decrease of extraction yields and N, O, phenolic OH, and organic free radical contents. These effects are generally more evident after the first year of slurry application and tend to disappear with increasing number of treatments. Most probably, over the years the slightly humified slurry HA is mineralized through extended microbial oxidation, whereas only the most recalcitrant components, such as S-containing, phenolic, and aliphatic structures, are partially accumulated by incorporation into soil HA.
在半干旱条件下的田间试验中，研究了以两种施用量（90和150立方米·公顷⁻¹·年⁻¹）每年连续三年添加猪粪对土壤和土壤腐殖酸（HA）的影响。采用标准方法对土壤和猪粪进行分析。通过基于碱性萃取、酸性沉淀至pH 1、反复碱性溶解和酸性沉淀进行纯化、水洗、透析以及最终冷冻干燥的常规程序，从土壤和猪粪中分离出HA。对获得的HA进行元素（C、H、N、S和O）和酸性官能团（羧基和酚羟基）组成分析，并通过紫外可见光谱、傅里叶变换红外光谱、荧光光谱和电子自旋共振光谱进行分析。与对照土壤相比，施用猪粪的土壤具有更高的pH值和电导率，总氮含量略高，C/N比值较小。仅在以较高猪粪施用量改良2年和3年的土壤中观察到总有机碳含量下降。与对照土壤HA相比，猪粪HA的特点是含硫和含氮基团含量较高，酸性官能团和有机自由基含量较低，具有普遍的脂肪族特征，分子异质性扩展，芳香族缩合和腐殖化程度较低。用猪粪HA改良会使土壤HA发生一系列变化，包括碳、硫和羧基含量、C/N比值以及脂肪族性增加，萃取率以及氮、氧、酚羟基和有机自由基含量降低。这些影响在施用猪粪的第一年之后通常更为明显，并随着处理次数的增加而趋于消失。很可能多年来，轻度腐殖化的猪粪HA通过广泛的微生物氧化而矿化，而只有最顽固的成分，如含硫结构、酚类结构和脂肪族结构，通过掺入土壤HA中而部分积累。
