不同施肥方式下滩涂围垦农田土壤有机碳及团聚体有机碳的分布

通过在苏北滩涂地区开展田间试验,研究了不同施肥处理(不施肥、施农家肥、商品有机肥、无机肥)对滩涂地区围垦农田土壤有机碳及团聚体有机碳的影响。结果表明,与对照相比,不同施肥处理均能明显增加0~30 cm土层土壤有机碳含量和有机碳密度,施农家肥增加幅度最高,增加值分别为0.66 g kg-1和0.07 kg m-2。试验地区水稳性团聚体以5 mm和0.25~0.5 mm为主,含量分别为37%~57%和13%~20%;随着土层深度增加,5 mm团聚体含量降低,0.25~0.5 mm团聚体则增加;农家肥能显著增加5 mm团聚体含量,同时降低0.25~5 mm团聚体含量。团聚体中有机碳含量表现为,除0.25~0.5 mm团聚体外,5 mm至0.5~1 mm团聚体之间,粒径越小,有机碳含量越高,其中0.5~1 mm团聚体有机碳含量最高,为6.83 g kg-1;与其他处理相比,农家肥的施用能明显增加各粒级团聚体中有机碳含量。试验地区土壤有机碳含量与5 mm团聚体及其有机碳含量极显著正相关(p0.01),而与0.25~5 mm团聚体负相关(p0.01或p0.05)。

Effects of fertilization on soil organic carbon and distribution of SOC in aggregates in tidal flat polders

Soil organic carbon (SOC) content has long been recognized as an important indicator of soil quality. Soil aggregates are considered as the basic structure of soil. Soil aggregation and SOC accumulation are interrelated: SOC or its fractions are basic to aggregation process, whereas SOC sequestered within aggregates is protected against decomposition. This relationship between aggregates and SOC is considered as an important mechanism of physical protection of SOC. A number of studies have been conducted by scientists at home and abroad, focusing on distribution of SOC in aggregates in paddy soils, black soils, and degraded soils. However, few have reported about effect of fertilization on SOC distribution in aggregates in coastal saline soil. In this paper, an experiment was carried out in a field of coastal saline soil in North Jiangsu, to study effects of fertilization on soil organic carbon and SOC distribution in aggregates various in size. The experiment was designed to have four treatments: no fertilizer (CK), farm yard manure (FYM), commercial organic fertilizer (COF) and inorganic fertilizer (IF), and three replicates for each treatment. Soil samples were collected from the 0~10, 10~20, 20~30, 30~40, 40~60, 60~80, 80~100 cm soil layers, and then air-dried, and ground to pass a 0.15 mm sieve for determination of soil organic carbon with the oxidation method using potassium dichromate in 0.4 mol L-1 K2CrO7-H2SO4 solution. Distribution of water-stable aggregates was measured according to Haynes (1993). Analysis of variance producers were conducted using the SPSS statistical procedures. Results show that all the treatments were obviously higher than CK in content and density of soil organic carbon in the 0~30 cm soil layer, with Treatment FYM, in particular, which increased the content and density by 1.96 g kg^-2and 0.23 kg m^-2, respectively. The water-stable aggregates in the studied field were dominated by those >5 mm and 0.25~0.5 mm, in particle size, which accounted for 37%~57% and 13%~20%, respectively. The fraction of >5 mm decreased in content, while the fraction of 0.25~0.5 mm increased along with soil depth in all the treatments. Treatment FYM significantly increased the content of the fraction of >5 mm, but decreased that of the fraction of 0.25~5 mm significantly. Distribution of SOC in aggregates was found to be that in aggregates varying from 0.5~1 mm to >5 mm in particle size, the smaller the aggregates, the higher the SOC content therein. The fraction of 0.5~1 mm size was the highest (6.83 g kg^-1) in SOC content. Compared with all the other treatments, Treatment FYM increased SOC content in all the fractions of aggregates. In the experiment field, SOC content in the soil was a positively related to that in the fraction of >5 mm (p <0.01), and negatively to that in the fraction of 0.25~5 mm (p <0.01 or p >0.05).