Abstract:In the forming process of paddy soil derived from red earth,transformation and movement of matter are proceeded under the conddtions of oxidation-reduction and periodical alternation of drying and wetting in which the submerging reduction is dominant.The condition not only promote the accumulation of organic matter,but also the ratios of E.H./T.H.and H.A./F.A..The reaccumulation of bases can make the acid and base-unsaturated red earth develop info paddy soil derived from red earth with very high degree of base saturation.The eluviation process induced by oxidation-reduction and compleaation result in redistribution of chemical elements in solum and alleviate the allitic process of red earth,which are favorable for maturation and Fertility promotion of paddy soil.The soil physical properties and characters of soil profiles are also changed due to the conditions mentioned above.The pcrcosubmergic horizon with cloddy structure,coatings and the obvious illuviation of Fe and Mg is formed.Soil structure and fertility are improved.The changes mentioned above are positively related to the years of planting rice.The forming process of paddy soil derived from red earth could be divided into two stages,i.e.the stage of embryonic pattern due to submerged condition and the stage of transitional pattern due to perco-genetic process.The perco-genetic paddy soil with basic characteristics of paddy soil can be formed preliminaryly in ten years.

Abstract:Experiment of evaporation of soil water were carried out in the polymethylmetha-crylate cylinders with diameter of 5 cm and length of 200 cm.The water in soils on loessal plateau is mostly in the status of suspended water.Therefore,the upward movement of water by evagora}tian in souls on loessal plateau belongs to unsaturated flow.Under the unsaturated condition the evaporation process of soil water is considered the movement of one-dimensional vertical flow.

Abstract:A numerical model of ane-dimensional flow through unsaturated homogeneous soil has been developed to simulate the water movement in soil a deep ground-water table under the initial and boundary conditions.This method can be used for the study of the infiltration,evaporation,transpiration and redistribution of water in soil profile as well as the water movement process while these phennmeaa appear alternatively.The modelling experiment programmed with FORTRAN has been carried out on g computer M-150 and verified by laboratory tests.Using this the following were calculated:(1) comparison between the steady and fluctuating evaporation,(2) water regime in profile versus steady rain infiltration in soil,and (3) variation of water in soil profile during growing period of wheat.

Abstract:The clay mineral composition of two pairs of yellow earth and red earth derived from granite in Quangdong were analysed qualitatively and quantitatively by X-ray and chemical methods.In the profiles of two red earths,the composition of clay mineral in the fraction <2 μm varied insignificantly,containing about 50-55% kaolinite,20% amorphous materials and gibbsite and small amount of hydromicas,mixed-layer mineral and mineral of 14Å.In addition,the whole profile of red earth in Jianfengling still contained small amount of smectite.On the contrary,the composition of clay minerals of yellow earth differed from that of red earth,which contained more mineral of 14Å and hydromica,with less kaolinite.However,the composition of clay mineral of two yellow earths also varied greatly.The yellow earth with lower weathering degree taken from Yangchun contained mainly mineral of 14Å and hydromica,its kaolinite content less than 15%;while the yellow earth with higher weathering degree taken from Jianfengling contained mainly kaolinite,being as much as 40%,but still contained a certain amount of minerals of 14Å and hydromica.Smectite was not found in the solum of these two yellow earths,only small amount of smectite was discovered in regolith of granite.Mineral of 14Å in the yellow earth belonged to intergradient mineral,that is vermiculite with unegchangeable hydrozy-Al interlayer.Due to organic matter in the surface soil hydrosy-Al interlayer will be removed easily,which indicates that organic matter is unfavourable for the formation of hydroxy-Al interlayer in swelling mineral.The granite residual materials of yellow earths contained much more halloysite,less kaolinite and a certain amount of gibbeite.Besides,there also existed some smectite and calcite in granite residual materials of Yangchun,this indicated that smectite may be formed in the early weathering stage of granite,if calcium exist.

Abstract:Experiments on decomposition of residues of plants including various cereal crops,leguminous and aquatic green manure crops under field conditions were carried out on microplots of paddy soils and upland soils in Guangzhou (southern subtropics) and Wuzi (northern subtropics) respectively.The fraction of originally added plant C retafined in soil after the decomposition for 1 or 2 years was,as what has been previously found in the study at southern Jiangsu,correlated positively with the lignin content of plant residue regardless of different enc-ironments in which it decomposed,but it was related neither to its nitrogen content nor to its water-soluble substances content.For a given plant residue,the decomposition pattern in Guangzhou was very similar to that in Wuxi.Moreover,the decomposition rate of plant residue in Guangzhou was as fast as that in Wuxi,although the mean annual temperature and precipitation in Guangzhou were 6.4℃ and 550 mm higher than those in Wuxi respectively.Evidence obtained indicates that this is due to the lower pH value of soils in Guangzhou.It was found that in case of the same soil used for the decomposition experiments both in Guangzhou and Wuai,its decomposition rate in Guangzhou was significantly faster than thntin Wuri.

Abstract:The present paper deals with the inhibition of free NH₃ formed by urea hydrolysis in calcareous soil and acid soil with low content of potassium.It is showed by experimenu that the toxic symptom of plant leave were similar to K deficiency,the root developments of wheat,corn and rice were inhibited significantly,without any root hairs and new roots grown,appearing yellow-brown colour on root tip sometimes.Plant root was injured clearly while NH₃ concentration was 5 μg/cm³,however the root could recover its normal growth gradually after removing NH₃ treatment.While the root was treated by NH₃ with a concentration up to 30 μg/cm³ for 6 hours,root normal growth could no longer be recovered.Rice had higher resistance ability to free NH₃ than wheat.K⁺ and some amino acids could be released from root tissue injured by NH₃.The amount of K+ released from corn should be up to 4% of root dry weight.It indicates that permeability of cell membrane may be influenced by NH₃.Furthermore,plant root was injured both by top dressing N of 200 ppm or band applying urea of 187,5 kg/ha in calcareous soil.At the 10th day after applying urea at late tillering stage,the dry weight of wheat roots was less than that in check (without urea treatment),while the similar tendency could be observed in acid soil under the condition of potassium deficiency.It indicates that plant root growth injured by free NH₃ is related to potassium disorder in plant.It is suggested that the urea applied should be covered with soil before seedling or the fertilizer should be applied in strip separated from the seeds or urea applied mixed with peat,All these measures are of advantage to prevent plants from the togieity and the loss of NH₃.

Abstract:The results of this study indicated that the composition and properties of soil humus were closely related to their formation conditions,and had zonal regularities.Data obtained showed that the composition of soil humus in virgin soils varied with different soil zones.For geographical distribution from black soil to red earth,the optical density elementary composition,C/H ratio and aromaticity of humic acids in the soils all had certain zonal regularities.According to the results mentioned above,the soil humus substances appear to tend to be simple from the north to the south.As compared with the virgin and dry farming soils,paddy soil had a higher content of organic matter and HA/FA ratio,but a lower content of active humic acid.It indicates that the hydrothermal conditions under rice planting are favourable for the aecumulation of organic matter,and change the composition of soil humus.However,the anaerobic condition of paddy soil is a factor inhibiting the decomposition and condensation of organic matter in soil,which results in the formation of humic substances with smaller molecule and low-degree of humification.Calculation of the correlation coefficients between E₄,E₄/E₆ ratio and elementary composition,C/H ratio,oxygen-containing functional groups and aromaticity show that E₄ value is not only significantly correlated with C%,O%,phenolic-OH-O%,quinone O%,but also with C/H ratio and aromaticity.It is also indicated from these results that E₄ value might be regarded as an index of aromaticity of humic acids.

Abstract:The present paper is to inyestigate the rate and process of arsenate adsorption and desorption,and the energy of arsenate adsorption by some soils in Shaangi Province.A two-constant rate equation (C=k·C₀·t^1/m)developed by Kuo and Lotse is better than five equations,i.e.firstrorder reaction,second-order reaction,third-order reaction,parabolic diffusion and the elovich equations used for fitting the experimental data.Sectionally fitting by two-constant rate equation can further improve the goodness of fit.The activation energy of adsorption calculated according to the Arrhenius equation was 0.7-34 kcal/mole.The relatively low activation energy suggests that adsorptian of aasenate in the soils might probably be a physical process,which obviously dffifens from the chemical reaction in true solution.The rate and capacity of adsorption and desorption by soils are affected by incubating time,temperature,ratio of solution and soil,concentration and amount of As added,and soil characteristics.Clay soil has a higher adsorption rate constant (k),and higher adsorption amount than sandy loam.But the sandy loam has a higher desorption rate constant (k_-1),so arsenate is more easily released from soil into solution.

Abstract:The effect of the addition of Cd,P and Zn compounds on the yields of rice grains,plant shoots and the content of mineral nutrients in straw and Cd concentration in brown rice were studied in the greenhouse.P increas}ad the yields of rice grains and plant shoots,while Cd,Zn and interaction of P and Zn decreased them.There are similar 1near regression equations for the yields of rice grain and plant shoots.The linear regresaion equation for rice grain is:Y=17.24+0.0466(P)-0.1850(Cd)-0.1115(Zn)-0.0005(P-Zn)with R²=0.97^**,where Y is grain yield (g/plant);(P) is concentration of added P (mg/kg);(Cd) is concentration of added Cd (mg/kg);(Zn) is concentration of added Zn (mg/kg);(P-Zn) is interaction of P and Zn.The mineral nutrients in rice straw were markedly affected by all treatments.The Cd concentration in brown rice increased with the increase of concentration of Cd,Zn and P added.However multiple linear regression analysis shows that only the Cd effect is the most significant.The Cd concentration in brown rice shows a highly significant correlation (r=0.75^**) with Cd in air-dried soil at harvest extracted by 0.05 M HCl.The toxicological evaluation of Cd concentration in brown rice are discussed.

Abstract:The nitrogen fixation,activities in soil cores of rice rhizosphere were measured by the acetylene-reduction method.As calculated according to the theoretical value of the ratio of acetylene reduced to N fined (3:1),the amount of nitrogen fined in paddy field of early rice ranged from 200-226 g per mu for 66 days and that of late rice from 301-398 g per mu for 72 days respectively,in which about 80-90% of N₂ was fined from the heading to ripening stages for early rice and 40-52% of N₂ was fixed during the same growing period for late rice.The results of experiments showed that the nitrogen fixation activity in rice rhizosphere varied with different parts of root.The highest activity was found at the basal part of stem connect with root system buried in soil about 2.5 cm,the lower was at the roots below basal stem about 3 cm in soil and the lowest was at the roots near root tip.Among the heterotraphic bacteria associated with rice plant routs,nitrogen-fixing organisms was dominant,with a few Clostridium butyricum.

Abstract:磷素在橡胶树的整个新陈代谢过程中占有极为特殊的地位。生产实践证明,橡胶树施用磷肥一般能提高产量4—21%。磷素能提高橡胶种子的发芽率,促进根系的伸长、树围的增粗和树皮的再生,还能增进橡胶树的抗寒抗旱能力。胶园土壤中磷素供应不足时,橡胶树的生长发育受到限制,开割橡胶树的胶乳产量、质量下降。严重缺磷时,如橡胶叶片含磷量在0.14外以下,橡胶树树冠的中层或上层的某些叶片前半截的表面呈古铜色或浅红色,背面则呈浅紫色症状,甚至出现叶尖上卷焦灼,顶芽死亡的情况^{[2 8.9]}。因此,对我国植胶区磷素营养的研究,具有重要的生产意义。

Abstract:地球的腐殖质层是太阳能的巨大贮存库,在陆地的生物能量贮存中,约有50%含于腐殖质中。因此土壤中的有机质转化是最有意义的能量转化过程之一。此外,土壤肥力水平除与腐殖质的数量有关外,腐殖物质的组成、特性也是重要的影响因素。能态是腐殖物质的一种重要特性,腐殖物质能态的研究有助于加深对腐殖物质特性的认识。因此研究土壤腐殖质形成过程的能量转化,以及不同条件下土壤腐殖物质的能态特征具有重要的意义。

Abstract:某些作物所摄取的钾,约有90%是通过扩散作用移向植物根表后而吸收的,因此测定土壤中K⁺的扩散系数,对了解K⁺向根运移的速率就具有实际意义。对扩散系数的测定国内常用的是同位素冰冻切片法和同位素针筒法,此二法需应用同位素,难于推广。国外早期提出的离子交换树脂膜法^[4-6],曾用以测定了土壤中各种营养离子的扩散系数,近年又应用于田间钻孔土壤的测定^[7,8],但均未介绍具体测定方法。我们根据斐克第二扩散定律,对K⁺扩散系数的计算公式进行了推导并拟定了一个测定方法,现将初步结果报道如下。