黑土和白浆土上磷肥肥效与土壤性质和氮素供应水平的关系

一般认为磷肥施入土壤后,能迅速地转化成难以被作物利用的状态.武玫玲等人^[1]指出,可溶性磷酸盐施入土壤2小时后,有40%转化为0.5N HAc不能溶解的状态,经过一个月增加到80%以上.许多研究亦指出,土壤可溶性和交换性盐基的性质和含量^[2]、土壤粘土矿物组成^[3]、土壤的pH值^[4]、影响化学平衡的时间、温度和水分舍量等^[5],都可影响磷肥的转化过程.陈魁卿等^[6]认为,黑土中的活性铁铝合量与磷酸的吸收没有规律性;而白浆土<0.01毫米的物理性粘粒与磷肥吸收关系较大.综上可见,磷肥肥效受到土壤诸因子的制约.     

土壤吸收量是土壤肥沃度的一项重要指标

土壤吸收性能的研究,自上世纪Way,Bemmelen 以来,吸引过很多土壤化学家的注意,诸如К.К.Гедройц^[1],А.Н.Соколовский^[9].Н/П/Ремезов^[8],Н.И.Горбунов^[3]等。     

华北平原瓦碱的特性和形成

华北平原广泛分布着一种具有灰白色紧实结壳的土壤,群众称为瓦碱(或岗瓦碱)。这种土壤在冀^[1]、鲁^[2]、豫^[3]、苏^[4,5]、皖^[6,7,8]五省都有分布,一般认为这是一种碱化土壤,但其性质及形成过程还不够清楚。根据国内外的研究资料,碱化土壤多分布于栗钙土、黑土及棕色荒漠草原土带,至于褐土带地区浅色草甸土发生碱化过程,在土壤学研究中还是一个新问题。因此,我们曾对山东、河南某些瓦碱进行了一些工作,今将初步结果报导如下。     

土壤酶活性的总体在评价土壤肥力水平中的作用

土壤酶学的研究,从一开始便与土壤肥力的研究紧密地结合在一起.本世纪五十年代初,Hofmann^[5]提出了用土壤的酶活性作为衡量土壤的生物学活性和生产力的指标.其后,Lajudie与Pochon^[8]指出,根据土壤蛋白酶活性进行的分类,能较好地反映土壤的表观肥力.Moureaux^[9]在研究了许多土壤的转化酶活性后,也提出了类似的见解.     

磷肥在土壤中的转化及其与土壤有效磷的关系

自从张守敬和Jeckson(1957年)提出土壤无机磷分级方法以来,国内外许多土壤农业化学家对土壤有效磷与各级无机磷之间的关系^[1],作物吸磷状况与土壤无机磷组成的相关性^[2],水稻生长期间土壤有效磷增加的机理^[3],以及磷肥对土壤无机磷组成的影响和转化等方面作了广泛的研究^[4]。     

无结构土壤透气性的初步研究

土壤的透气性是指土壤让空气穿透本身的能力。透气性是土壤很重要的物理性质,因为它不仅决定了土壤与大气间空气交换的速度^[1],而且和土壤的持水性有关^[2],测定土壤的透气性还可以了解土壤其他一系列的物理性质如排水的能力^[3]、地表迳流的速度^[2]、耐蚀性、空气容量^[3]及其结构性的程度等等。土壤中微生物活动的方向与强度、种籽的发芽、根系的发育及其吸收能力、土壤中养分的状态^[4]和影响农作物生活的其他重要土壤因素都有赖于土壤的透气性。     

土壤中活跃眞菌菌丝的捕捉和常见种类的简易识别法

土壤中以菌丝状态存活的真菌是活跃的生物类羣之一.它们在土壤中具有多方面的作用^[1].有关这类真菌的分离方法曾有不少人研究过^[2],但至今还没有一个被公认的简易有效的方法,使土壤真菌研究工作的进展受到一定的限制.     

土壤空气研究概况

土壤空气是土壤物理学研究领域内比较薄弱的一个分支学科^[3].但是,它在土壤形成过程中和土壤肥力的培育过程中却占有十分重要的地位.Вернаднский^[7]曾以“无气体不成土壤”这句话来表达土壤空气与土壤之间的相互关系.     

云贵高原土壤地理分布规律

土壤地理分布规律的研究,前人已做过不少工作.早在1899年B.B.道库恰耶夫便提出了土壤地带性学说^[1],继后,普拉索洛夫等先后论述了土壤水平地带、垂直地带的普遍性和基本规律,提出了土壤相性(省性)的科学概念,从而为研究土壤地理分布规律奠定了基础^[1,2,3].解放后,马溶之等运用B.B.道库恰耶夫的土壤地带性原理,结合我国土壤分布的具体特点,研究了中国土壤地理分布的普遍规律,为研究云贵高原土壤地理分布打下良好的基础^[4,5].     

旱地加水可促进微生物对γ-666的降解

γ-666在含水率低的旱地土壤中持留期可长达3—11年之久,并可引起水质、土壤和植物的污染^[1]。从60年代以来,许多学者对渍水土壤中微生物对γ-666的降解作用已作了大量研究^[1-7]。确定渍水土壤中γ-666的降解比旱地土壤容易得多^[1-3],并先后分离到了二株嫌气性降解菌^[2,4,7]。     

坡面汇流汇沙与侵蚀—搬运—沉积过程

侵蚀、搬运和沉积过程是土壤侵蚀过程中相互影响又相互制约的三个子过程。自从 2 0世纪 40年代Ellison[1～ 4] 将水蚀过程分为四个子过程 ,即雨滴侵蚀过程、径流侵蚀过程、雨滴搬运过程和径流搬运过程以来 ,许多学者从不同角度对其进行了研究。Meyer和Wischeier[5] 及Meyer和Fo     

THE IDENTIFICATION AND DETERMINATION OF GLUCURONIC AND GALACTURONIC ACIDS IN SCOTTISH SOILS AND SOIL FRACTIONS USING ION-EXCHANGE AND GAS-LIQUID CHROMATOGRAPHY

Two methods have been used for the identification and determination of uronic acids in soils and soil fractions. The uronic acids were released by hydrolysis with sulphuric acid. After partial purification by ion-exchange chromatography they were separated either by further ion-exchange or by gas-liquid chromatography of derivatives. The latter method is preferable for determination of the specific activities of uronic acids in soil tracer work. Both galacturonic and glucuronic acids were detected in the four Scottish soils examined, the galacturonic acid being present in slightly greater amounts in each soil. Mannuronic acid was not detected. The total amount of uronic acids found ranged from about 4 mg to 6 mg/g soil.     

甲酸甲烷杆菌和甲烷八叠球菌的分离和特征

本文介绍从德国哥廷根污水处理厂腐化塔污泥中分离出的两株甲烷细菌，其中一株为甲酸甲烷杆菌（Ｍｅｔｈａｎｏｂａｃｔｅｒｉｕｍｆｏｒｍｉｃｉｃｕｍ），其细胞杆状，可利用甲酸或Ｈ２／ＣＯ２作为碳源和能源，另一株为甲烷八叠球菌属（Ｍｅｔｈａｎｏｓａｒｃｉｎａ），其细胞球状，成堆排列，可利用甲醇或Ｈ２／ＣＯ２作为碳源和能源。     

有机无机肥配施对小麦吸收氮磷及土壤肥力的影响

￣（１５）Ｎ示踪试验表明，有机无机肥配施促进了有机叉的矿化和小麦对有机氮的吸收利用，基施氮肥主要用于营养器官的形成，返青追肥主要用于生殖器官的形成。有机无机氮肥配施提高了总氮生产效率。配施处理小麦对磷素的吸收总量稍高于单施无机氮肥处理，磷素在籽粒中的分配率稍低于单施无机氮肥处理是导致磷素生产效率下降的重要因素。有机无机肥配施提高小麦产量的同时也培肥了地力，是小麦高产稳产的重主措施之一     

MAKING SOIL AND WATER CONSERVATION SUSTAINABLE: FROM COERCION AND CONTROL TO PARTNERSHIPS AND PARTICIPATION

For close to a century, rural development policies and practice have taken the view that farmers are mismanagers of soil and water. This paper reviews the history of farmers being advised, paid and forced to adopt new soil and water conservation measures and practices. Many have done so, and environments and economies have benefited in the short term, but ill-conceived policies and badly designed programmes and projects have undermined these efforts in the name of conservation. Most efforts have been remarkably unsuccessful, often resulting in more erosion. They have undermined the credibility of conservation and wasted huge sums of money. For a new era of soil and water conservation, new initiatives are showing how to make conservation sustainable. Farmers are now considered the potential solution rather than the problem, and so the value of local knowledge and skills is being put at the core of new programmes. This involves a major focus on building farmers' capacity to innovate and develop technologies appropriate to their own conditions. Local organizations are strengthened through participatory processes, this participation being interactive and empowering. Recent evidence is indicating that these new interactions between professionals and farmers are producing considerable productive and sustainable benefits. For widespread impact, enabling policy frameworks are still needed to encourage the spread of more sustainable practices for agriculture. © 1997 John Wiley & Sons, Ltd.     

水肥耦合对小麦玉米带田产量效应及土壤水分动态研究

采用3414最优回归设计方案,研究了水肥耦合对小麦玉米带田产量效应及土壤水分动态规律。结果表明：不同水肥耦合模式对带田作物的产量差异达极显著水平。在灌水量4800m3/hm^2,施氮肥420kg/hm^2,磷肥120kg/hm^2的处理（W2N2P2）中,带田产量和水分利用效率达最高值,决定带田总体产量性状主要因子为氮...     

黄土与古土壤中重金属的存在形态及风化成土作用对其影响

本文采用了七步连续萃取方法，研究了洛川黄土剖面黄土与古土壤中Ｆｅ，Ｃｕ，Ｚｎ，Ｃｏ和Ｎｉ五种重金属的存在形态。结果表明：黄土与古土壤中上述元素主要存在于残余态和晶形，无定形氧化铁的结合态中，而且线性回归分析表明Ｃｕ，Ｚｎ，Ｎｉ与晶形氧化铁之间存在关；ｃＵ，ｃＯ，Ｎｉ与无定形氧化铁之间存在相关；黄土风化为古土壤后，碳酸盐结合态的重金属含量增加是古土壤相对于黄土重金属增加的主要原因。     

稻草和尿素配施时水稻对肥料氮和土壤氮的吸收利用

利用＾１５Ｎ同位素示踪技术,研究了稻草和尿素配施时水稻对肥料和土壤氮的吸收。结果表明,稻草单施导致土壤速效氮的生物固定,氮素供应不足是影响水稻分蘖成穗的限制因子,稻草配合尿素施用,明显改善肥料氮和土壤氮的供应,既有利于当季水稻增产,也有利于培养土壤肥力,还有利于后茬物作产量的提高 。     

MIGRATION AND AGGREGATION OF Na AND Ca CLAYS BY THE FREEZING OF DISPERSED AND FLOCCULATED SUSPENSIONS

The ability of clay to move ahead of an ice-liquid interface depends on the rate of freezing, the particle size, the release of dissolved air from the water through its probable effect on local freezing rates, and on the electrolyte and its concentration through their effects on interparticle forces and particle mobility. A freezing-rate of 1 cm per hour did not move flocculated clay in most cases, but moved dispersed clay up to 0.7 cm before being trapped in the ice with released air. Aggregates of clay (0.1 to 1 mm) were produced by freezing. After thawing they swelled and dispersed depending on the electrolyte and its concentration in a similar manner to aggregates formed by drying.     

SELECTIVITY AND PARTITIONING OF POTASSIUM AND SODIUM IN SESAME

Net uptake and partitioning of sodium (Na⁺) and potassium (K⁺) in plants of two sesame cultivars (Sesamum indicum cv. ‘PB-1’ and cv. ‘UCR’) exposed to 20 mM sodium chloride (NaCl) were studied over a period of 28 days. Both cultivars showed a marked discrimination between K⁺ and Na⁺ during uptake. The reduction of K⁺ in the plants caused by the NaCl treatment was of similar magnitude in the two cvs. The cv. ‘UCR’ showed lower Na⁺ concentrations in the shoot tissues than ‘PB-1’ and K⁺/Na⁺ selectivity ratios were higher in cv. ‘UCR’ than in cv. ‘PB-1’. At the last sampling on day 28 there was a marked decrease of shoot growth in cv. ‘PB-1’ in comparison to the cv. ‘UCR’. Leaves of cv. ‘PB-1’ showed clear toxic symptoms, while those of cv. ‘UCR’ did not. It is concluded that Na⁺ exclusion from the shoot contributes to salt tolerance of sesame, cv. ‘UCR’.