石灰性土壤硫形态及其生物有效性研究

Total 64 calcareous soils which originated from five parent materials, and collected from China were.to used to assess the sulphur fractions. Among of inorganic S fractions, slow soluble SO4-S ranged.from 0.02 to 142 mg S/kg soil with average 34 mg S/kg soil, accounted for 0.02-40% of total S,which was similar as soluble SO4-S of these soils, and adsorbed SO4-S least among these fractions.The extremely significant position relationship between the the contents of slow soluble S and.CaCO3 in soil was found [y (slow soluble S, mg/kg) = 5.8846 × (CaCO3 %，R2 = 0.4494**)].Analysis results of twenty two top-layer soils indicated that content of total S in soils was.214.0～760.5 (av. 405.5±111.8) mg/kg, among of which 59.8%～97.1% (av. 85.4%±10.0%) was organic S. The content of C-O-S, C-S and inert S in soils were 31.2～244.9 (130.3±64.6)mg/kg,.34.9～140.8 (65.5 ± 29.4)mg/kg, 16.7～394.4(152.5 ± 96.7)mg/kg respectively, percentage of C-O-S, C-S and inert S in total S were 11.4%～56.7% (31.4%±12.9%), 5.0%～45.4% (18.0%±.10.7%) and 5.3～64.9%(36.0%±17.8%), and percentage of C-O-S, C-S and inert S in total organicS were 12.9%～62.6%(36.6±14.4%), 5.6%～51.2%(21.8±13.8%) and 8.5%～73.6%(41.5±19.1%).respectively. The significant position relationship between content of C-O-S (r=0.7334**), C-S (r=0.4426*) and organic C in soil were found..One experiment with eight treatments for two crops (wheat and rape) combined with two N forms (NO3-N and NH4-N), and with/or without the insoluble suphate -CaCO3 co-precipitate labelled with radioactive S35 was carried out under control environment conditions to assess the availability to crops of certain forms of sulphur in calcareous soil. Results of indicated 3-11% recovery S35 from the synthetic insoluble sulphate. A high recovery of S35 was obtained with the addition of NH4-N than with the addition of NO3-N. A obviously decrease of slow soluble SO4-S in soils taken in all treatments after harvesting crops was observed relative to their original.contents in study soil. The decrease of slow soluble SO4-S in soils for NH4-N form treatment was significantly greater than that for NO3-N form treatment. Addition S35 (13 mg S/kg soil) from synthetic slow soluble sulphate to wheat and rape increased concentration of S in plants in both.NH4-N and NO3-N treatments. The present indicated calcareous soil insoluble SO4-S was bioavailability. With application of NH4-N, wheat can use more insoluble SO4-S relative to rape..The effect of plant growth on the mineralization of organic matter and distribution of soil S fractions (plant available SO4 2-, adsorbed SO4.2-, carbon-bonded S, ester-bonded S and residual-S)in the rhizosphere was studied in a greenhouse experiment using a rhizobag technique. In this.study wheat, oilseed rape and radish were grown on two soils, a acid soil and a calcareous soil.Significant differences between S fractions in the rhizosphere and non-rhizosphere were.determined in dependence on soil type and crop species. In all cropped treatments lower amounts of ester-bonded S and higher levels of residual-S were found in the rhizosphere than in the.non-rhizosphere, while the amount of carbon-bonded S fractions was similar. These results indicate firstly, that the arylsulfatase activity was higher in the rhizosphere than in the.non-rhizosphere and secondly, that mass flow of SO4 2--S to the rhizosphere increased after mineralization of residual-S. Compared to the non-vegetated soil, the ester-bonded S fraction of wheat and oilseed rape decreased in the rhizosphere revealing that the mineralization of organic S.in the rhizosphere is related to the crop type.

建立石灰性土壤硫形态分级体系。探讨中国主要石灰性土壤硫形态分布特征及影响因素。深入研究石灰性土壤硫形态，特别是难溶形态硫（与碳酸钙共沉淀的硫酸盐）形成、转化规律，生物有效性大小及其调节机制。建立石灰性土壤缺硫诊断方法。为开展石灰性土壤硫素生物地球化学循环研究打基础，客观评价石灰性土壤硫肥力和指导硫肥的合理施用提供依据。