MODELLING OF SOIL PORES AS TUBES USING GAS PERMEABILITIES, GAS DIFFUSIVITIES AND WATER RELEASE

Two models are presented describing the air-filled continuous pores in soil and how they change with soil water potential. In the first model (A), the pores are represented by tortuous tubes of uniform radius. The radius, length and number are calculated from air permeability, relative diffusivity and air-filled porosity measured at each soil water potential. In the second model (B), the pores are represented by tortuous tubes of three radii joined at random in series. The radii and total lengths of the tube sections are estimated by comparison of air permeability, diffusion coefficient and air-filled porosity at each water potential with values calculated for a large number of theoretical systems. The models were applied to the results from undisturbed cores of a silt loam taken from 30 to 80 mm depth. For both models, the sequences of continuous pores were estimated to be 2 to 7 times as long as the sample but shortened as the sample dried. From the second model the average pore radius in direct drilled soil, 0.3 mm, was half that in ploughed soil and the minimum radius, 0.1 mm, was one-quarter that in ploughed soil.     

三种有机肥水溶性分解产物对铜、镉吸附的影响

研究了稻草、紫云英和猪粪的水溶性分解产物对铜和镉的沉淀作用及其在红壤和潮土上的吸附影响。结果表明三种水溶性分解产物对铜镉的沉淀及吸附有双重效应：铬合效应和ｐＨ提高效应。在相同的ｐＨ值条件下,有机分解产物通过络合作用而不同程度地抑制了铜和镉的沉淀作用及其在两种土壤上的吸附。由于铜具有较强的形成络合物的能力,所以有机分解产物对铜的抑制效果对于镉的抑制效果。吸附等温线表明,在不调节ｐＨ时,三种有机分解产     

利用土壤切片的数字图像定量评价土壤孔隙变异度和复杂度

研究结果表明 :利用土壤切片的数字图像 ,以孔隙周长和面积为基础数据 ,可以定量评价小尺度上的孔隙变异度 ,也可以对孔隙复杂度进行研究 ;土壤孔隙在mm尺度上也具有较高的变异度和复杂度 ;粒径 1～ 3mm和粒径 <2cm的重组土壤的孔隙在 2D空间多呈现网络状 ,而原状土壤的孔隙则多呈不规则的枝状或椭圆状 ;不同处理及不同土壤类型之间在孔隙周长、孔隙度以及孔隙变异度和复杂度方面存在不同程度的差异。     

低分子量有机酸对土壤磷释放动力学的影响

模拟植物在缺磷条件下,根系所分泌的有机酸种类和数量,用流动法研究了柠檬酸,苹果酸,草酸和酒石酸对土壤磷释放的影响。结果表明：有机酸能明显促进土壤中磷的释放,不同有机酸对石灰性土壤活化能力大小的次序为草酸≥柠檬酸〉苹果酸〉酒石酸;而对酸性土壤磷的释放量与Ｆｅ＋Ａｌ释放量之间呈极 相关,有机酸活化土壤磷能力大小的次序为柠檬酸〉草酸〉酒石酸〉苹果酸。     

贵州碳酸盐岩发育土壤磁学性质及其发生机理

本文对贵州碳酸盐岩发育土壤的磁化率、磁化率频率系数和等温剩磁等磁学参数的系统测定以及磁性矿物研究表明，碳酸盐岩发育土壤磁学性质及其变化特征主要受成土地球化学作用和环境影响，具有十分重要的环境指示意义。本文在采用高梯度磁性分离土壤中氧化铁矿物基础上，综合运用Ｘ射线衍射分析、电子探针分析、透射电镜和穆斯堡尔谱等方法，讨论了碳酸盐岩发育土壤中磁性矿物的形成机理。     

EFFECTS OF CULTIVATION ON SOIL WATER RETENTION AND WATER USE BY CEREALS IN CLAY SOILS

The effects are repotted of direct drilling and mouldboard ploughing on soil water retention and extraction in three soils over two to four years. In the years 1972–75 when winter rainfall was close to or greater than the long-term average the maximum soil water content of the upper 100 cm differed little between the cultivation treatments. In contrast, after the dry winter of 1975–76, about 10 per cent more water was stored in the direct-drilled soil, especially below 50 cm. In the following dry summer, winter wheat extracted up to 22 mm more water from uncultivated soil and this was associated with better growth of the crop than after ploughing. When simulated rain was applied, water infiltrated rapidly to a depth of 50–100 cm in direct-drilled soil, whereas on ploughed land its movement was retarded below the plough sole even when cultivation had been carried out under conditions which minimized smearing. Water storage at depth was consequently greater under dry conditions in the direct-drilled soil while excess water reached drain depth more rapidly in wet conditions.     

玄武岩母质发育的土壤上铜和锌的地球化学特征*

在成土过程中,铜和锌均有移动,迁移量铜大于锌,但这种作用小于母岩地球化学差异对总含量的影响。铜和锌的有效态含量,表土高于底土,海拔高处大于低处,pH值的影响作用并不显著。土壤中无定形铜含量与全铜量的比值,在富铝化程度相类似的土壤上随海拔升高而明显增大,即在红壤、黄红壤和黄壤之间有明显不同。无定形铜含量有随风化淋溶作用增强而降低的趋势。这些可作为土壤分类和肥力评价上的参考。     

SELECTIVE EXTRACTION OF AMORPHOUS IRON OXIDES BY EDTA FROM SOILS FROM DENMARK AND TANZANIA

Soils from Denmark and Tanzania were extracted with EDTA solutions of different concentrations and pH. After extraction for 3 months there was no significant (95% level) further increase in amounts of iron (and aluminium, calcium, and magnesium) during longer extraction periods. X-ray diffraction showed no change of the crystalline minerals caused by the extraction, which is believed to be specific for amorphous iron oxides. The EDTA method may thus serve as a reference method for the determination of amorphous iron oxides in soils. Although the difference between EDTA-extractable iron and that extracted during 2 h by ammonium oxalate at pH 3.0 in the dark may be high, the ammonium oxalate method is considered to give a fast and often fair estimate of amorphous iron oxides.     

豆科绿肥和化肥氮对双季稻稻田氧化亚氮排放贡献的研究

研究了大田条件下施用绿肥与化肥N后 ,双季稻区稻田土壤氧化亚氮 (N2 O)的排放。结果表明 ,在早稻生长季节既施绿肥又施化肥的处理 (VN)N2 O N的排放量高达 2 75kghm- 2 ,显著高于只施绿肥不施化肥 (V0 )、只施化肥不施绿肥 (FN)或既不施绿肥也不施化肥 (F0 )的处理 (后三者在早稻生长季节N2 O N的排放量分别为 0 2 9kghm- 2 、0 3 5kghm- 2 和 0 1 8kghm- 2 ) ,也显著高于在晚稻生长季节各处理N2 O N的排放量 (VN、V0、FN和F0处理分别为 0 3 4、0 2 6、0 2 8和 0 2 3kghm- 2 )。绿肥不仅影响稻田土壤N2 O的排放量 ,还影响其排放模式。VN处理N2 O的排放主要集中早稻生长季节的中期烤田之后 ,其它处理则在整个水稻生长季节均有排放。在早稻生长季节绿肥与化肥N间还存在极显著的交互效应。     

从磷酸盐位探讨土壤中磷的固定机制及其有效度问题

最近几年来,我国矿质磷肥施用量年年都有大幅度增加。但从同位素研究及全国试验结果来看,一般作物当季对过磷酸钙中磷的回收率只有10-30%左右(中国科学院南京土坡研究所,1978)。     

土壤对铜离子的专性吸附及其特征的研究

供试土壤专性吸附铜的等温线均符合Langmuir方程。红壤吸附量最低,砖红腹与黄泥土最大吸附量相近,但在铜浓度低时砖红壤吸铜量远低于黄泥土,而在高浓度则反之。土壤专性吸附铜是在溶液中Na⁺浓度比Cu²⁺高8.3—100倍条件下,Na⁺离子仍不足以与之竞争的那些专性吸附点所吸持的铜。按其解吸条件区分为松结合铜(可为N NH₄Cl解吸)和紧结合铜(仅能为0.1 N HCl解吸)两种。紧结合铜受平衡溶液铜浓度影响很小,所占据的吸附点对Cu²⁺有较强亲和力。松结合铜则随平衡铜溶液浓度增大而增加,符合Langmuir方程。对于砖红壤和黄泥土,在铜浓度低时紧结合铜>松结合铜;浓度高时则反之。红壤专性吸附铜始终以松结合铜为主。三种土壤比较,紧结合铜是砖红壤>黄泥土>红壤;松结合铜则是黄泥土>砖红壤>红壤。造成这些差别的原因可能与土壤性质、氧化物、有机质和粘土矿物组成等不同有关。用平衡法研究三种土壤专性吸附铜在不同浓度NH₄Cl和HCl溶液中的解吸表明,可进一步区分为三或四种不同的结合状况。红壤对铜吸附容量最小,且最易解吸。     

THE EFFECT OF CULTIVATION ON THE STRUCTURE AND OTHER PHYSICAL CHARACTERISTICS OF GRASSLAND AND ARABLE SOILS (194–970)

Cultivating grassland changes the physical state of the soil. The paper describes observations and measurements made in the field and the laboratory on a wide range of soils (with series names) in England over a period of 25 years. Dry sieving showed that natural weathering of grassland aggregates after three months'exposure was very considerable. The drawbar-pull on ploughing soil recently out of grass, as compared with old arable, increased with the number of years out of grass. The number of earthworms per hectare on old grassland was 6 to 9 times that on old arable of the same soil series: after three years'cultivation it was reduced by about a half. The possibility of erosion by wind increased with the number of years out of grass. Old arable land on gentle slopes had its resistance to flowing water (sheet erosion) much increased by as little as 2 years under grass. The apparent densities of soils were at a minimum under old grass and increased under cultivation. On some soils arable for many decades, the apparent densities were near those considered limiting for root penetration. The volurne of water per cent in the soil at the sticky point decreased as the years out of grass increased, suggesting a decrease in the number of days the soil could be cultivated without smearing. The water-stability of soil aggregates decreased as the number of years after ploughing old grassland increased. Whatever the texture, on ploughing old grassland, the water stability of air-dry aggregates feil sharply in the first – years and then approached the value corresponding to that of old arable soils more slowly, apart from soils of low clay content in which it differed little from old arable land after 2 years. Measurement of changes in water stability and field observations in a 6-course rotation (3 years ley, 3 years cereal) on a loam which had been in a similar rotation for about a decade after old grassland, suggested that this balance was probably right for maintaining such a soil at a good cropping level. Puddling (poaching) by animals of wet arable loam soils overlying clay resulted in gleying to the surface: ferrous iron was detected chemically. On putting down to grass there was little increase in water stability of the aggregates after 4 years. The reduction in the total pore space caused by harvesting machinery and also as a result of some years'cultivation of grassland was considerable. The ease of penetration of soils when taking cores was compared by counting the number of blows to drive in a corer: the number was much less in a soil recently out of old grass compared with old arable. The root development of cereals was poor in old arable silt soils very unstable to wetting and drying and with few visible biopores (> 10–00 μm). On soils with many visible pores, root development was much greater and yields with similar rates of nitrogen were double. The total N in the soils feil when old grassland was ploughed, sometimes by as much as 75 per cent in about 20 years. There was sometimes a significant corre-lation between total N and the reduction in water-stable aggregation during the years following ploughing grassland: the correlation coefficient was much higher on ploughing old grassland rather than leys. The N level dropped much more quickly in the first few years after ploughing old grassland than later. All single-property measurements give only a limited assessment of the physical state of a soil. Soils can be assessed satisfactorily only by making a range of measurements appropriate to the farming System.     

土壤的干湿变异与片状结构的发展

一、片状结构形成的原因很多,但在地表常见的一种可能不是沉积、水冻或压力等原因造成,而系常经干湿变异的结果。二、在干湿变异条件下产生的片状结构分布地区甚广,可能其形成与土壤种类无直接关系。凡地面少植被、原缺乏结构的土壤,如不受人为翻动,露于地面一定时期后,多半会产生不同明显程度的片状结构。三、土壤在干湿变异条件下产生片状结构可能为一简单的机械作用。即土块湿润时膨胀,体积变大,再经干燥,体积不能恢复,留下横向裂隙于土中,遂成片状结构。在所研究的各因子中,干湿变异次数多、干湿变异程度大以及干湿变异中脱水速率快均能促使土块膨胀,所以能使片状结构形成更为明显。如对土块施以压力,不予膨胀,虽土块具有各方面生成片状结构的良好条件,仍不能形成片状结构。对田间具片状结构土块的试验中,说明它可能与室内人工片状结构有相同的成因,一方面也说明了这种结构的不稳定,易于破坏,但如条件适合,形成也不困难。四、此种片状结构因系土块干燥时产生横向裂隙所形成,所以结构横轴生成的方向主要决定于水分的蒸发面而经常与之平行。这种关系在野外具体表现为结构横轴常与地表平行,在室内的几项试验结果与此也相符合。此外结构横轴形成的方向是否与土块湿润时水分进行的...     

POLYCARBOXVLIC ACIDS EXTRACTED BY WATER AND BY ALKALI FROM AGRICULATURAL TOP SOILS OF DIFFERENT DRAINAGE STATUS

Water-ex tractable poly carboxy lie acids and alkali-extractable humic acids and fulvic acids, were isolated from agricultural top-soils of two soil associations. Samples from four soil series from each association were selected with drainage status varying from well-drained to very poorly-drained. The amounts of atkali-extractable humic acid and water-ex tractable polycarboxylic acids were highest in the very poorly-drained soils whilst the amounts of alkali-extractable fulvic acid were generally similar in all the soils, although the fulvic acid accounted for a lower proportion of the total organic matter in the poorly-drained soils. Oxalate-extractable aluminium decreased with increased drainage impedance, whilst no such trend was observed for oxalate-extractable iron. It is suggested that the fulvic acid-like polycarboxylic acids are removed from the soil solution by adsorption onto sesquioxides; so that the lower content of aluminium oxides in the very poorly-drained soils results in depressed levels of fulvic acid and increased concentrations of water-extractable polycarboxylic acids.     

THE VOLATILISATION, FROM SOILS AND MIXTURES OF SOIL COMPONENTS, OF IODINE ADDED AS POTASSIUM IODIDE

Iodine, as potassium iodide in solution, was added to samples of 24 surface soils, 15 subsoils and 16 mixtures of sand with other materials representing soil components, at 10 μg iodine/g soil. The extent of volatilisation of the added iodine was measured after 30 days' exposure in a well-ventilated room. With many of the surface soils volatilisation was negligible although with an acid sandy podsol it amounted to 57 per cent of the iodine added. Eleven of the subsoils induced volatilisation amounting to > 10 per cent of that added. With sand alone, having a pH of 5.7, volatilisation amounted to 100 per cent, and with the mixtures it ranged from nil to 100 per cent. Organic matter reduced volatilisation, probably by retaining the iodine in bound form. Montmorillonite, kaolinite and ferric oxide also reduced volatilisation in comparison with sand alone, but had less effect than did organic matter. Calcium carbonate, although in general reducing volatilisation, probably through its influence on pH and hence on retention by other materials, caused no reduction when added to sand alone.     

水稻田干耕及湿耕对于土壤中氮素转化及水稻产量的影响

1.在南京低丘地区,发育于黄土性母质上的轻度潴育性水稻土,在水旱连作的栽培制度下,本田耕地,通过干耕晒垡过程,并无效果。2.本文对不同类型水稻土干燥后的铵态氮动态,进行了测定和讨论,认为对于还原性强烈而腐殖质较多的水稻田,干耕晒垡是发挥水田潜在地力的有效措施,且只有在土壤充分干燥情况下,才能加速土壤有机质的矿化过程,但是,对于一般腐殖质含量较低,而无显著沼泽化迹象的轻度潴育性水稻土,由于土壤氧化势较高,土壤本身对促进有机物的分解具有良好条件,在田间情况下,对于耕作上某一短期的土壤干燥过程,不易产生较为明显的效果是可能的。3.对于水稻生长期间,土壤中NH_4~+及NO_3~-的动能进行了初步分析和讨论,初步指出,在长江下游地区,水田肥力的发挥,可能在很大程度上有赖于对土壤矿化过程的促进。     

中亚热带两种水稻土土壤养分空间变异的对比研究

20世纪90年代中后期以来，随着“3S”技术和地统计学方法越来越多地应用于我国土壤学领域，以及“精准农业”（Precision agriculture）在我国的引进和部分地区的初步应用，对土壤特性尤其是土壤养分空间变异性的研究日益引起学者的关注，其中以北方土壤及管理种植模式为研究对象的较多，南方相关方面的研究报道较少。从理论上讲，在田块面积相对较小、田块间土壤养分变化较大的中国南方地区，比发达国家土壤养分相对一致的大农场和我国北方地区更需要应用养分精准管理技术。     

用电导热散法研究可变电荷土壤粘粒与离子的相互作用

本工作选用二种可变电荷土壤粘粒(<2μ),分别含有0.35×10^-4-1.3×10^-4mol/L的不同电解质,在不同含水量下,在5—50℃范围内测量其直流电导率的变化。试验结果表明,电导热散法是研究土壤粘粒与离子相互作用的有用手段;电导率-温度曲线上的折点温度是随含水量、电解质种类和土壤类型而不同。在相同含水量下,含有不同电解质的红壤体系的折点温度具有如下的变化顺序:CaCl₂>Na₂SO₄>KCl>Ca(NO₃)₂>NaNO₃;砖红壤体系的折点温度明显高于红壤体系。折点温度的高低是土壤粘粒与离子相互作用强度的反映。     

不同施肥处理土壤胡敏酸及其级分与蒙脱石的吸附特征 Ⅱ. 蒙脱石对胡敏酸不同级分的吸附

采用酒精沉淀法，反不同施肥处理土壤胡敏酸分7个级分，研究了胡敏酸不同级分与钙饱和蒙脱石的吸附特征。结果表明，蒙脱石对胡敏酸各级分的吸附可用单表面Langmuir、双表面Langmuir和Freundlich方程来描述。各级分的吸附量和吸附强度不是随级分数变化单一递增或递减，在7个级分中，级分4、3的吸附量和吸附强度较大，是吸附最佳级分。说明级分4、3具有与蒙脱石胶体最佳的成键吸附状态，是吸附最佳分子状态，有机肥处理，吸附最佳级分的吸附性状（吸附量和吸附强度）优于化肥、无肥处理。     

红壤对铝、锰离子的吸附特征Ⅱ铝、锰离子的非电性吸附

对铝、锰离子的非电性吸附进行了Freundlish方程处理 ,结果表明 :砖红壤中的吸附较红壤明显 ,低浓度时 ,锰离子的非电性吸附较铝离子为弱 ,高浓度时则反之 ;对于土壤的离子交换吸附 ,似不可能获得稳定的平衡常数k ;K表征离子的吸附强度 ,以膨润土中者最大 ,1/n是吸附量与溶液浓度的相关率 ,K和 1/n成反相关。砖红壤中的ΔGo 最大 ,铝、钾离子交换的ΔGo 大于铝、钙离子交换者。非电性吸附量及与其有关的k、K、1/n和ΔGo 既受固相表面性质的影响 ,也制约于离子的本性