Abstract:Net mineralization of N in 16 soil samples in cluding three types of soil (loessal soil,cinnauwn soil and fluvo-aqruuc soil) was determined over 154-day period at 35℃, using incuhartion intervals of 7, 7, 14, 28, 28, 28, 42 days. For most soils, cumnlatirve net N mineralized is linearly related to the srluare root of time, t^1/2. The N mineralization potential, No, of each soil was calculated by the mathematical models of G, Stanford and S.J. Smith, and J. Richter, using the data, derived from the incubatian experiment. The results obtained indicated that the N mineralization potential, N₀, could reflect N-sup-paying capabilities of soils;the No constituted 10.8-23.4% of total N in soil;the constant of N mineralization rate, k, averaged 0.0064±0.0006 day^-1.

Abstract:Mineralization and immobilization of soil nitrogen were studied by incubation methods with labelled nitrogen. Results showed that deoamposition of organic nitrogen in soil was not accelerated by the mineral nitrogen added;however, the mineral nitrogen added in soil accelerated the biological immobilization of the nitrogen added, and, at the wane time, lowered the immobilization of soil nitrogen. Therefore, there was no dietinct fluctuation of the total immobilization nitrogen in soil in the whole period of in-cwbation. It seems that the increase of the net mineralized nitrogen in soil induced by mineral nitrogen added, which is generally Known as the priming effect, is mainly because part of soil nitrogen to be immobilized is replaced by mineral nitrogen added in soil.

Abstract:Phosphate coated urea (PCU) with a ttotal N content of 33.8%, total P content of 5.15% and available P content of 4.10% was prepared and used in pot and field experiments in comparison with the commercial slow-release fertilizers including sulfur coated urea (SCU),isobntylidene diurea (IBDU) and urea supergranule (USG) under rice-wheat rotation system. The results obtained are summarized as follows:(1) PCU and USG applied in holes as basal fertilizer in pot experiment was markedly higher in supplying intensity and capacity of N than SCU and-IBDU mixed with soil as basal fertilizer during the growing period from transplanting to milky ripening stage of rice, which indicates that the supplying process of N from PCU applied in hole as basal fertilizer well coincides with the requirement of N by rice plant im different growing stages. (2) Effect of PCU deeply applied as basal fertilizer on the yield of middle rice was significantly higher than that of common urea by split application, but it on the yield of single late rice on permeable and bleached paddy soils was lower than that of eommon urea of split application. The effect of slow-release fertilizer on wheat yield in pot experiment was more significant than that on rice yield, but no difference was found in field experiment.(3) PCU applied in holes as basal fertilizer for middle rice on red earth was the highest in recovery rate of N, amounting to 79%;and the recovery rates of N from USG, SCU and common urea were 60%, 42% and 34% respectively. The recovery rates of N from the slowerelease fertilizers by single late rice were lower, while that by wheat was higher than that by rice;and the results obtained in pot experiment was higher than those in field experiment.(4) The residual effect of IBDU with the lowest release rate of N was higher by 89% and 47% than those of PCU and SCU respectively, which implies that the residual effect of the fertilizers is related with the release rate of the fertilizers. It was also found that the residual effect of the fertilizers in pot experiment was significantly higher than that obtained in field experiment.

Abstract:The content, composition and properties of the organic matters in soils under different vegetations in Wolong Natural Reserve, Sichaun Province were studied. Main results obtained are summarized as follows.1. Althoughthe the soils are under different bio-climatic conditions, their humus comositions belong to fulvic acid type. 2. Raw humus in the soils under deciduous broadleaved forests, coniferous and broadleaved mined forests and dark coniferous forests belong to fulvic acid type.The infrared spectra and ultraviolet spectra indicate that the raw humus is obviously different from "mature" humus acid. 3. The soil organic matter content is closely interrelated with the physical properties and the available nutrient of the soil.

Abstract:The stability constants of Fe(Ⅱ)-complexes were determined on the basis of the shift in peak potential during the reduction of Fe²⁺ in the presence of eomplexants. The log K values for soil solutions ranged from 2.6 to 4.5. A chang of pH by 1 unit induced a change of log K by 0.92 unit on average. Aeration of the soil solution led to an increase in logK value. The logKvalues for Fe(Ⅱ)-complexes were larger than those for Mn(Ⅱ)-complexes by about 0.8 unit.

Abstract:In this paper the contents and distribution patterns of rare earth elements (REE) in soils are discussed based on the analytical data of 20 soil samples collected from Yinji loess profile in Shaanxi Province. There are five buried soils in the loelss profile with a thickness of 39.7 m.. The fifth horizon Qonsists of three closely overlapping buried soils.The contents of La, Ce, Nd, Sm, Eu, Tb, Dy, Tm, Yb and Lu in soils were determined by instrumental neutron activation analysis (INAA),and the contents of other elements by chemical method. The results showed that the total REE contents of the 20 samples ranged from 157 to 231.68 ppm with au average of 199 ppm, which is close to the contents in shales of north America. The REE contents in various developed horizons of the loess profile were different, but they tended to be, approximately identical after having eliminated the interference of CaCO₃. It seems that the CaCO₃ played a diluent role in various layers.The loess is continental deposits generally rich in the elements of Ce family, with,imilar REE distribution patterns and no remarkable segreaatian in various layers. All these indicate that the loess either in its oribinal region or in the accumulated region has been under dry and asriated conditions since long before, which inevitably results in its weak eluviation process.

Abstract:In the present paper, the magnetic sasceptibility (m. s.) of red earths, lateritic red earths, latosols, young calcareous soils and paddy sails in subtrapie aad tropic China is reported.. The m. s. is greatly influenced by parent rocks. The m. s. values of red earths and latosols derived from basalt and andesite amount to 300-500 units and even Up to 2000-6000 units (10^-6 emn/g).Those of red earths and latoeols on granite and ether acid magmatic rocks amount to 40-100 units, and those of red earths and latosols on limestone, shale, sandstone and tuff amonat only to 10-40 units mostly.

Abstract:Eight soil samples of permeable paddy soil collected form Tai Lake Basin were investigated. The main results are summarized as follows: 1. The clay minerals of the clay fraction in the soils are predominated by hydromica, ka.olinite and montmorillonite. 2. There is distinct difference in the distributions of clay minerals between the coars clay fraction (0.002-0.001 mm) and fine clay fraction(<0.001 mm). 3. The sand fraction (1-0.05 mm) containing "iron-manganese sands" is less in SiO₂ and more in Fe₂O₃ than the silt fraction (0.05-0.002 mm),and it is also higher in volume magnetic/susceptibility than the silt fraction. 4. Plasticity and swelling start to be found only in the clay fraction(<0.002 mm). All the properties of the permeable paddy soil mentioned above are similar to those of bleached 0paddy soils reported by the authors in 1982, but different from those of the upland soils raported by others.

Abstract:Soil suitability evaluation and rational utilization modes were studied. IIainan Island was divided into 4094 grids which were regarded as the soil resources units to be evaluated. Of the 4094 grids, 570 were chosen as typical ones (trained samples) and further divided into 8 groups representing the successful soil utilization modes on the Island (i.e. paddy field, upland field, forestry 1, forestry 2, tropical cropland 1,tropical cropland 2, pasture and others). 11 variables (i.e. evaluation items including altitude, Soil type humus reserves, solum thicl;ness and slope, et.c.) were selected and rcasonablely dibitized for ca,lcula.tion. Aftsr stepwise multfiple diseriminant analysis, all 11 varubles were proved effective, while 8 initial groups were further a.djust.ed to the optimum. The adjusted groups constituted soil suitability evaluation criteria. Based on discriminant funnetions, other 3464 grids were allocated into corresponding optimum groups. A rational soil utiLization map of the Islaud was output automatically by computor. In addition, a map of sail utilization regionalizatibn wets finished. On the m.ap, 7 utilizalion regions were delimitated. It is concluded that the Island possesses great. potentiality of developing tropical crops, agriculture and forestry.

Abstract:This paper deals mainly with method of elimination of interference of iron and oxelate by nitric acid-perchloric acid for polarographic determination of available moly-bdenum in soil. The procedure is described briefly as follows:2g of soil sample is extracted with 20 ml of ammonium ozalate and oxalic acid solution (pH 3.3),shake for 8 hours as conventional way (or shake for 30 minutes and allow it to stand over night).Transfer 1 ml of the extract into a 25 ml beaker. Evaporate to dryness. Add 10 drops of nitrie acid (0.05 ml per drop) and 2 drops of perchloric acid. Evaporate to dryness at higher temperature. Cool and (1:1). Evaporate just to dryness, dissolve the residue with 5 drops of hydrochloric acid cool and dissolve the residue with 1 ml of 2.5 M sulpnuric acid and 1 ml of 0.5 M phenylhydroxyacetic acid, and then add 8 ml of saturated solution of potassium chlorate, and miz evenly. Measure the peak height with JP 1 A polarobraph. The prucodnrc is very simple and rapid with satisfactory accuracy and precision. The method can be used for direct determination of available molybdenum in acid, neutral, and alkaline soils without separating iron.

Abstract:华南植物园位于广州市东北郊,约在北纬23°10'与东经113°21'附近,属于南亚热带季风气候区,地形为丘陵河谷平原,海拔在20—30米之间,典型的地带性土壤是赤红壤。园内分为植物展览区和试验区两大部分,引种栽培各种热带、亚热带植物但在火炉山和青山等丘陵、台地仍有次生的亚热带常绿阔叶林和一部分灌木草本植物,是我国著名的热带、亚热带植物引种驯化的试验研究基地,普及植物学知识的园地,同时也可作为我国南亚热带土壤,植被特征的一个代表。因此,对该园土壤的研究,在科学研究和生产实践上都有一定的意义。

Abstract:苯并(a)芘(BaP)是强致癌物。因此,它在环境中的分布已日益受到重视。BaP主要来源于有机物的不完全燃烧,在燃烧过程中,BaP的形成机理Badger曾提出过没想,主要包括热裂解与热合成。首先有机物在高温下裂解产生碳氢自由基,结合成乙炔,由乙炔形成乙烯基乙炔,或1,3一丁二烯,然后芳环化成乙基苯,再进一步结合成丁基苯和四氢化蔡,最后通过中间体形成BaP。不管这一设想是否完美,但已证实有机物在燃烧时,710℃是BaP合成的最适温度。