不同林龄和连栽代次杨树人工林土壤氮矿质化特性

采用好气培养间歇淋洗的方法,研究了江苏苏北地区不同林龄（1代4年生林地、1代10年生林地）和连栽代次（1代4年生林地、2代4年生林地）的杨树人工林土壤及农田无林地土壤在20和30℃培养条件下氮素矿质化特性.结果表明,各样地土壤经4周培养的矿化量为36.70~95.63 mg.kg-1,平均矿化速率约为1.31~3.42 mg.kg-1.d-1.林龄和连栽代次对杨树人工土壤的矿质化作用有明显的影响,其中主要是对硝化作用的影响,而对氨化作用影响不明显.与1代4年生林地相比,1代10年生林地土壤矿化累积量和硝化累积量分别降低了11%~17%和13%~20%;而2代4年生林地土壤则分别降低了39%~43%和45%~49%,显示连栽代次对土壤矿质化作用的影响更加明显.各样地土壤矿化速率和硝化速率在培养的第1周最高,然后随培养周期迅速降低;而氨化速率则是在第2周达到峰值,然后逐渐降低.随林龄和连栽代次的增加,土壤矿化速率和硝化减小,尤其是培养第1周,而氨化速率差异不显著.各样地30℃培养条件下的土壤矿化量和矿化速率均明显高于20℃,表明培养温度对土壤矿质化作用具有明显的影响.

苏北杨树人工林连栽林地土壤氮素矿质化原位研究

采用土柱离子交换包法,研究了苏北地区不同连栽代次杨树人工林土壤氮矿化的状况及耕作措施对二代杨树林土壤氮矿化的影响。结果表明:不同代次的杨树人工林土壤氨化速率的季节变化较为一致,二代林土壤的氨化速率和一代林相比,并未出现明显的降低,有的月份(4、7月)甚至高于一代林。二代林的硝化速率和净氮矿化速率明显低于一代林,尤其是在3、4、5月份。耕作措施虽然增加了二代林土壤氮素年氨化量、硝化量和矿化量,但由于也相应地增加了年淋溶量(约占年矿化量的49.15%),因此土壤中的无机氮含量反而低于免耕处理。

Spatial Heterogeneity of Soil Mineral Oxide Components in Depression Between Karst Hills,Southwest China

In karst regions,the spatial heterogeneity of soil mineral oxides and environmental variables is still not clear.We investigated the spatial heterogeneity of SiO2,Al2O3,Fe2O3,CaO,MgO,P2O5,K2O,and MnO contents in the soils of slope land,plantation forest,secondary forest,and primary forest,as well as their relationships with environmental variables in a karst region of Southwest China.Geostatistics,principal component analysis(PCA),and canonical correlation analysis(CCA)were applied to analyze the field data.The results show that SiO2was the predominant mineral in the soils(45.02%–67.33%),followed by Al2O3and Fe2O3.Most soil mineral oxide components had a strong spatial dependence,except for CaO,MgO,and P2O5in the plantation forest,MgO and P2O5in the secondary forest,and CaO in the slope land.Dimensionality reduction in PCA was not appropriate due to the strong spatial heterogeneity in the ecosystems.Soil mineral oxide components,the main factors in all ecosystems,had greater influences on vegetation than those of conventional soil properties.There were close relationships between soil mineral oxide components and vegetation,topography,and conventional soil properties.Mineral oxide components affected species diversity,organic matter and nitrogen levels.

Uptake of Organic Phosphorus by Arbuscular Mycorrhizal Red Clover

The capacities of two arbuscular mycorrhizal (AM) fungi, Glomusmosseae and Glomus versiforme, to mineralize added organic P werestudied in a sterilized clacareous soil. Mycorrhizal (inoculated witheither of the AM fungi) and non-mycorrhizal red clover (Trifoliumpratense L.) plants were grown for eight weeks in pots with upperroot, central hyphal and lower soil compartments. The hyphal and soilcompartments received either organic P (as Na-phytte) or inorganic P(as KH_2PO_4) at the rate of 50 mg P kg^-1. No P was added to theroot compartments.

^(15)N NMR Spectroscopic Study on Nitrogen Forms in Humic Substances of Soils

Nitrogen forms of humic substances from a subalpine meadow soil, a latentic red soil and a weathered coal and the effect of acid hydrolysis on N structures of soil humic substances were studied by using 15N cross-polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy. Of the detectable 15N-signal intensity in the spectra of soil humic substances 71%-79% may be attributed to amide groups, 10%-18% to aromatic/aliphatic amines and 6%~11% to indole- and pyrrole-like N. Whereas in the spectrum of the fulvic acid from weathered coal 46%, at least, of the total 15N-signal intensity might be assigned to pyrrole-like N, 14% to aromatic/aliphatic ammes, and the remaining intensities could not be assigned with certainty. Data on nonhydrolyzable residue of protein-sugar mixture and a 15N-labelled soil fulvic acid confirm the formation of nonhydrolyzable heterocyclic N during acid hydrolysis. Project (No. 39790100) supported by the National Natural Science Foundation of China.

Influence of Long Term Fertilization with Different Mineral Fertilizers and Farmyard Manure on Some Soil Chemical Properties and Crop Yields *1

A long term fertilization experiment was carried out in an experimental field in Lyczyn near Warsaw, Poland. Application ofmineral fertilizers, especially N fertilizers with and without farmyard manure accelerated the acidification process of the soil. Application of 1.6 t CaO ha -1 every four years was essential to maintenance of the soil pH KCl at 5.5～6.6 and base saturation degree above 60%. Application of 50 t farmyard manure ha -1 every 4 years, which contained 46 kg P and 240 kg K, was sufficient to maintain both the K and P fertility of the soil. Besides, it was beneficial to alleviating soil acidification. As a result of long term unbalanced fertilization, yield responses to N, P and K fertilizers increased significantly with time. The efficiency of N from farmyard manure was found to be comparable to that of N fertilizer during 1988～1991.

Main Clay Minerals in Soils of Fujian Province, China

The clay minerals of more than 200 soil samples collected from various sites of Fujian Province were studied by the X-ray diffraction method and transmission electron microscopy to study their distribution and evolution. Montmorillonite was found in coastal solonchak, paddy soils derived from marine deposit, lacustrine deposit and river deposit, and some latentic red soil, red soil and yellow soil with a low weathering degree. Chlorite existed mainly in coastal solonchak and paddy soil developed from marine deposit. 1.4 nm intergradient mineral appeared frequently in yellow soil, red soil and latentic red soil. The content of l.4 nm intergradient mineral increased with the decrease of weathering degree from latentic red soil to red soil to yellow soil. Hydrous micas were more in coastal solonchak, paddy soils derived from marine deposit, lacustrine deposit and river deposit, and purple soil from purple shale than in other soils. Kaolinite was the most important clay mineral in the soils in this province. The higher the soil weathering degree, the more the kaolinite existed. From yellow soil to red soil to latentic red soil, kaolinite increased gradually. Kaolinite was the predominant clay mineral accompanied by few other minerals in typical latentic red soil. Tubular halloysite was a widespread clay mineral in soils of Fujian Province with varying quantities. The soil derived from the parent rocks rich in feldspar contained more tubular halloysite. Spheroidal halloysite was found in a red soil and a paddy soil developed from olivine basalt. Gibbsite in the soils in this district was largely 'primary gibbsite' which formed in the early weathering stage. Gibbsite decreased with the increase of weathering degree from yellow soil to red soil to latentic red soil. Goethite also decreased in the same sequence while hematite increased.

Effect of Clay Minerals on the Chemical Characteristics of Soil Humus

Chemical characteristics of humic substances in soils with different mineralogical characteristics and under different utilization patterns in Zhangpu, Fujian Province,together with two pairs of cultiwted soils in North China Plain were studied by chemical analysis,visible and IR spectroscopy and 13C NMR spectrometry.For soils in Zhangpu the HA/FA ratio and both the aromaticity and the degree of hundfication of HA were higher in soils with montmorillonite as the predominant clay mineral than in thO6e with kaolinite as the predominant clay mineral, provided these soils were under the same utilisstion pattern. While for eaCh pair of soils with similar mineralogical characteristics the HA/FA ratio was higher and the C/H ratio and the content of carboxyl group of HA were lower in paddy soil than in upland soil.Among the upland soils(or paddy soils) studied the HA/FA ratio of soil in Zhangpu with kaollnite as the predominant clay mineral was the lowest,and that of soil in Zhangpu with montmorillonite aa the predominant clay mineral was the highest.It was concluded that the presence of moatmorillonite favored the formation and maturation of humic acid.

Residual Effect of Long Term Application of Organic and Mineral Fertilizers on Selected Chemical Properties of a Savanna Alfisol

The residual effect of organic and mineral fertilizers on selected chemical properties of an Alfisol in the long term soil fertility trial established in 1950 at Samaru, Nigerian savanna was assessed. The trial was left fallow for fourteen years due to lack of funds. Topsoil was collected from plots that received three levels of cow dung （D）, nitrogen （N） and phosphorus （P） in all possible combinations. The soils were analyzed for selected chemical properties. Except for significant effect of applied P on available P, sole application of cow dung, N or P had no significant effect on all the measured soil properties. The interaction of D and P significantly affected the mean values of exchangeable Ca, Mg, K and ECEC in the range of 1.12-1.96, 0.62-1.11, 0.37-0.64 and 2.82-4.11 cmol/kg respectively. The most important results were the ability of the plot that received neither D nor P to significantly increase these parameters than the plots that received only one of the treatments. The results show that the fallow period has changed the effects of application of organic and mineral fertilizers on the soil chemical properties under continuous cultivation by modifying them towards those of a native savanna Alfisol.

Soil Quality Degradation in a Magnesite Mining Area

Fourteen soil properties in 17 sampling sites were analyzed to study the soil degradation in a magnesite mining area in Halcheng City, Northeast China. Such areas have hitherto received little attention. The current practices of magnesite mining in this area resulted in degradation of soil quality and specifically led to an increase in soil pH, the ratio of magnesium to calcium, bulk density, clay dispersibility, total magnesium and equivalent calcium carbonate and a decrease in surface soil porosity and available phosphorous. The soil quality in the areas affected by intensive mining activity was obviously worse than that of areas far away from the mine. Four factors were identified and ＂magnesium factor＂, ＂pH factor＂ and ＂fertility factor＂, involving 13 soil properties, explained 82~0 of the total variance in the entire data set. Discriminant analysis showed that the total magnesium, water-soluble calcium and available phosphorous were the most sensitive indicators for soil quality.

Can Biochar Protect Labile Organic Matter Against Mineralization in Soil?

Biochar could help to stabilize soil organic （SOM） matter, thus sequestering carbon （C） into the soil. The aim of this work was to determine an easy method i） to estimate the effects of the addition of biochar and nutrients on the organic matter （SOM） mineralization in an artificial soil, proposed by the Organization for Economic Co-operation and Development （OECD）, amended with glucose and ii） to measure the amount of labile organic matter （glucose） that can be sorbed and thus be partially protected in the same soil, amended or not amended with biochar. A factorial experiment was designed to check the effects of three single factors （biochar, nutrients, and glucose） and their interactions on whole SOM mineralization. Soil samples were inoculated with a microbial inoculum and preincubated to ensure that their biological activities were not limited by a small amount of microbial biomass, and then they were incubated in the dark at 21 ~C for 619 d. Periodical measurements of C mineralized to carbon dioxide （CO2） were carried out throughout the 619-d incubation to allow the mineralization of both active and slow organic matter pools. The amount of sorbed glucose was calculated as the difference between the total and remaining amounts of glucose added in a soil extract. Two different models, the Freundlich and Langmuir models, were selected to assess the equilibrium isotherms of glucose sorption. The CO2-C release strongly depended on the presence of nutrients only when no biochar was added to the soil. The mineralization of organic matter in the soil amended with both biochar and glucose was equal to the sum of the mineralization of the two C sources separately. Furthermore, a significant amount of glucose can be sorbed on the biochar-amended soil, suggesting the involvement of physico-chemical mechanisms in labile organic matter protection.

Anthracene Removal and Mineral N Dynamics in a Surfactant-Amended Soil

Surfactants, such as non-ionic Surfynol 485 （ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol）, have been applied to accelerate removal of polycyclic aromatic hydrocarbons from soil. This study investigated the dissipation of anthracene, and carbon （C） and nitrogen （N） mineralization in soil amended with non-ionic Surfynol 485 at different rates. Soil samples of a Typic Fragiudept taken from Otumba, Mexico were spiked with anthracene at a final concentration of 520 mg kg^-1 dry soil using acetone as solvent, amended with 0.0, 24.9, 49.8 or 124.4 g kg^-1 soil of the surfactant and incubated in the laboratory. The soil not amended with anthracene, acetone and the surfactant was used as a control. Dynamics of C and N and the concentration of anthracene were monitored for 56 d. After 56 d of incubation, 38% of the anthracene was removed from the unamended soil, and 47%, 55% and 66% of the anthracene were removed when 24.9, 49.8 and 124.4 g kg^-1 of the surfactant were applied, respectively. Application of acetone, anthracene or surfactant increased the emission of CO2, but decreased the mineral N compared to the unamended control. Applying the surfactant to the acetone or anthracene-amended soil reduced emission of CO2, but increased the mineral N at the lower application rates of the surfactant. It was found that the application of the non-ionic surfactant increased the bioavailability of anthracene and thus its removal from soil, increased C mineralization, but decreased N miaeralization. Consequently, the application of non-ionic surfactant could be easily used to accelerate the removal of pollutants from hydrocarbon-contaminated soils, but mineral N in the soil would decrease, which might inhibit plant growth.