THE POTASSIUM STATUS OF MALAWI SOILS

Twenty surface soils from four main Soil Groups in Malawi and their sub-soils were divided into three groups based on cation exchange capacity (group I, CEC < 50; group II, 50–100; and group III > 100μeq g^–1). In each soil group the maximum amounts of K removed by successive extraction with 0.005 M CaCl₂ solution were well related to the potassium potential pK–0.5p(Ca + Mg), exchangeable K, ‘step K’, and the quotient ‘step K’/CR.K, where CR.K is ‘constant-rate’potassium. In Group III soils only, ‘step K’/CR.K values were significantly correlated with pH, clay, and CEC, and this suggested that the soils were relatively rich in K⁺ specific binding sites. In 27 soils from an NPK factorial experiment on tea, the rate of depletion of extractable K reserve increased with ammonium sulphate treatment, whereas K fertilizers tended to off-set significantly (P= 0.001) the depletion of K reserve. The values for the change in free energy ΔG =RT In a_K/ (a_(Ca+Mg)) ^½, ranged from –12 to –16 kJ mol^–1, and field observations showed that tea plants growing on soils having ΔG values less than –15 kJ mol^–1 responded to K fertilizers. The investigation has indicated that heavily cropped soils are likely to show crop responses if the intensive cropping system does not include supplementation of K.     

DISPERSION, MECHANICAL COMPOSITION, AND FRACTIONATION OF WEST INDIAN VOLCANIC YELLOW EARTH SOILS (ANDEPTS)

Methods of dispersion used in Japan and New Zealand for soils formed on recent volcanic ash (Andepts) which involved adjusting the pH of organic matterfree soil suspensions to 4 or 10·5 were not effective on similar soils in the Caribbean. Partial dispersion was obtained by adjusting the pH to between 2 and 3 but lower (down to pH 1) and higher (up to pH 11·1) pH values were ineffective. Substantial amounts of Al dissolved at pH 1–3 probably as a result of some disintegration of the allophanoid minerals. Zirconium nitrate solutions were very efficient in causing dispersion, a concentration of 12 me Zr being necessary for complete dispersion of 20 g samples of soil. Excess Zr did not adversely affect dispersion but resulted in depression of pH of the suspensions. The high ionic charge, small atomic radius, and low ionization potential of Zr apparently resulted in saturation of the cation exchange capacity and some isomorphous substitution of Al leading to a net positive charge of the clay and an increase in anion exchange capacity. This was considered to be responsible for dispersion.     

棉花钾素营养与土壤钾素供应水平

大田试验和田间调查分别在杭州浙江农业大学实验农场黄松土(Semihy dromorphic soil)和金华盆地红壤上进行.品种分别为钱江9号和协作2号,这两处土壤有效钾含量均较低,棉花(Gosoypium hirsutum L.)生长不良,普遍早衰.根据土壤中交换性钾的含量与棉花生长情况,一般可分为四类:土壤交换性钾>90ppm,棉花生长正常,70-90ppm,潜在缺钾;<70ppm,明显缺钾;<50ppm,严重缺钾.棉花叶片含钾量与土壤交换性钾含量呈正相关,r=0.928,显著性超过1%水准.大田试验表明,施用钾肥能提高棉花叶片含钾量,增加叶面积和叶绿素含量以及CO₂的同化率;钾还能促进叶片中细胞色素氧化酶和硝酸还原酶的活性,提高气孔导度,降低水分的蒸腾速率.缺钾叶片结构松弛,角质层发育不良;正常叶片结构紧密,角质层发育良好.叶片含钾量无论在苗期、初花期、盛花期、花铃期,均与皮棉产量呈正相关,达到显著水准.     

GENESIS, MINERALOGY, AND RELATED PROPERTIES OF WEST INDIAN SOILS

The Montserrat series is one of the most fertile of tropical soils. Substantial amounts of exchangeable K, available P, and favourable organic matter content and distribution contribute to its unique properties. P occurs in amounts ranging from 0.4 to 0.6 per cent, about 75 per cent of which is inorganic with Fe phosphates making up the bulk. Truog's reagent almost quantitatively extracts Ca phosphate and Bray's and Olsen's reagents extract mainly Al phosphate. Exchangeable K is derived from glauconite. High exchangeable Ca and Mg contents derived from weathering of carbonates impart a favourable pH to the soil for plant growth. Exceptional structural stability to 120 cm depth is associated with high free iron oxide, organic matter, and Ca contents. The outstanding feature in mineral weathering is the rapid transformation of glauconite through vermiculite to kaolinite and the formation of goethite. Considerable interlayering occurs between vermiculite with sesquioxide coatings and mica-vermiculite interlayers. Much of this weathering occurs in the calcareous, oxidized, friable parent rock. The features of the Montserrat series described above substantiate its classification as a Brown Earth (Mollisol).     

我国南方一些土壤的钾素状况及其含钾矿物

本文研究了我国南方一些土壤的钾素状况及其含钾矿物。结果表明，土壤含钾矿物的含量和种类因成土母质和土壤发育程度而异。花岗岩发育土壤的含钾矿物随粒烃增大而增加（＞５０μ除外），沉积岩发育的土壤情况相反。土壤的非交换性钾与云母类矿物含量呈较好的相关性（ｒ＝０．６６９＾＊），交换性钾与土壤ＣＥＣ呈极显著正相关（ｒ＝０．８０８＾＊＊）。不同粒级对土壤全钾量贡献不一，花岗岩发育土壤的全钾量主要集中于１０－５０     

珠江三角洲土壤供钾能力的研究

珠江三角洲土壤钾素含量全钾平均1.68%,缓效性钾225ppm,速效性钾118ppm,在全省居中等水平.土壤有效钾含量不高.水平分布由三角洲前缘向顶部递减.水稻吸收缓效性钾越早,土壤供钾性能越差.水稻各生育期累积吸钾量变化呈开口向下的二次曲线,出现前轻、中重、后减弱规律.水稻中期吸钾越高,土壤供钾越好.土壤速效性钾变化呈开口向下的二次曲线,曲线变化越平缓,土壤供钾量越少.连续种植水稻吸钾总量占土壤有效钾贮量越多,供钾性能越差.粘质三角洲冲积潜育性水稻土,钾素的含量中上,土壤供钾性能好,早稻钾肥肥效不显著,晚稻极显著.粘质三角洲冲积沼泽性水稻土、粘质三角洲冲积盐溃强酸性水稻士钾素含量最高,但前者地下水位高,后者有酸害,影响水稻吸钾,钾肥肥效不显著.高度熟化粘质三角洲冲积潴育性水稻土等,土壤钾素含量,供钾性能较好,但生产性能高,需钾量大,钾肥肥效早晚稻极显著.沙质砖红壤性红壤潴育性水稻土,钾素含量和水稻吸钾量最少,供钾性能最差,钾肥肥效早晚稻十分显著.     

THE ORGANIC MATTER CONTENT OF THE SAVANNA SOILS OF WEST AFRICA

Published and unpublished data on the amounts of organic matter and nitrogen in the surface soils of the West African savanna are reviewed. In general, amounts are small; the mean carbon content of soils from 605 well-drained sites was 0.68 per cent. Two important factors governing amounts of organic matter in well-drained soils appear to be the clay content and a moisture factor related to the length of the wet season and represented here by mean annual rainfall. Multiple linear regression on soil clay content and rainfall accounted for 46.5 per cent and 57.2 per cent, respectively, of the observed variability of soil carbon and nitrogen contents. These findings suggest that the low levels of organic matter in savanna soils arise from their predominantly sandy nature and from the relatively low rainfall. In poorly drained soils organic matter levels are higher but are less significantly related to clay content and rainfall. The influence of human interference and of parent material and altitude on organic matter is demonstrated in the context of geographically limited areas within the savanna for which more detailed information was available.     

黄土区土壤钾的形态及其释放

本文研究了黄土区（陕西部分）土壤钾的形态,按毫克/100克土计,有机钾0.36-5.04,水溶性钾0.24-2.37,代换性钾3.61-16.96,有效钾3.85-19.33,非代换性钾64.45-149.77,结构钾1,840.3-2.538.3,全钾为1.920-2.640。有效钾为非代换性钾的11.42%,结构钾的0.53%和全钾的0.51%。水溶性钾和代换性钾分别是有效钾的8.2%和91.8%。通过主成分分析可知,土壤各种形态的钾与有机质呈正相关:水溶性钾、代换性钾、非代换性钾与有机态钾,代换性钾和非代换性钾与粉粒和粘粒也呈正相关,但都与沙粒呈负相关.钾的释放符合于幂回归方程（y=ax^-b）.释放量从北向南是逐渐增加的.幼年土壤和轻黑垆土耕作层释放量高于其他层次,但是粘黑垆土和黑土的粘化层的释放量高于其它层次。     

上海土壤磷素状况的研究

根据几年来的调查研究,上海地区土壤中全磷含量一般在0.13-0.18%,主要几种土壤的全磷量如表1。不同土壤的有效磷量(0.5M NaHCO₃溶性磷)。根据56个标本的测定结果,>22ppm(P₂O₅)占35.7%,12-22ppm为44.6%,<12ppm是19.7%。所以一般来说,约有三分之二的土壤有效磷含量在中等水平以下,作物对磷肥反应较明显,五分之一的土壤严重缺磷。因此近年来上海郊区,特别是一些高产单位对施用磷肥非常重视。     

耗竭条件下冬小麦的吸钾特点及其对土壤不同形态钾的利用

在耗竭条件下研究了冬小麦在我国11种主要土壤上的吸钾特点及其对不同形态钾利用。结果表明,冬小麦对钾的吸收具有明显的阶段性。拔节至齐穗期为吸钾高峰,成熟后出现排钾现象。耗竭条件下冬小麦各生育期土壤交换性钾含量变化不大,而缓效性钾从开穗后开始回升。冬小麦吸收的钾中,交换性钾占的比例较小,11种土壤平均为21.5％;1mol／LHNO3不能提取的钾占绝大部分,平均为78.5％。表明土壤经耗竭后,1mol／LHNO3不能提取的钟对作物钾营养的作用较大。耗竭后土壤交换性钾最低值出现的时期及数量大小是土壤重要的供钾特性之一。     

THE POTASSIUM STATUS OF SIX LOESSIAL SOILS OF CANTERBURY, NEW ZEALAND, IN RELATION TO RAINFALL AND RATE OF LOESS ACCUMULATION

A selection of greywacke-derived loessial soils in Canterbury, New Zealand, was examined to test the hypothesis that soil K status is a function of soil-forming factors. Soils were selected such that factors besides loess accumulation and rainfall were relatively constant and the effects of each variable could be isolated. Soil K status was evaluated by plant, chemical, and X-ray diffraction techniques. With increasing rainfall and decreasing rate of loess accumulation soil K status decreased; there was a concurrent decrease in illite and increase in interstratified mineral content of the clay fraction.     

THE CALCAREOUS SOILS OF AZERBAIJAN II. PHOSPHATE STATUS

The phosphate status, before and after P treatment in the laboratory, of surface soils from thirteen profiles of an Iranian catena, described in Part I, was investigated by determining the distribution of labile phosphate in solution and external and internal surfaces, and by examining their calcium phosphate solubility relationships. The labile P distribution of added P suggests generally that soils with most carbonate in the silt fraction (Part I) hold added P mostly on external surfaces, and those with increasing carbonate in the clay fraction, less so. Recovery of 200 and 400 mg/kg soil of added P in the labile phosphate was related to soil phosphate status directly and to the total carbonate area of the soil inversely. Solubility relationships indicated saturation with CaCO₃ and a compound approaching octacalcium phosphate in composition. The two saline-alkaline end-members of the catena from the Low Land area differed somewhat in having more of their P content in soluble and labile forms, and in storing added P uniformly on external and internal surfaces.     

不同土壤对钾的选择吸附特性

用K Ca交换平衡法对砖红壤、红壤、土、黑土和水稻土K的选择吸附特性研究结果表明 :KG 和KV 系数随着K Ca平衡体系中吸附相中钾与钙比率的变化而改变 ,其曲线特征说明土壤胶体存在着对K亲和力不同的吸附点位。在低钾饱和度时 ,土壤对K的高选择吸附主要归于粘粒矿物楔形区域电荷点位吸附 ,五种土壤楔形区域相对吸附点位顺序为 :黑土 >土 >水稻土 >红壤 >砖红壤 ,该相对吸附点位顺序与土壤含有风化云母和蛭石有关。在高钾饱和度时 ,五种土壤对K的吸附主要发生于粘粒矿物的晶层表面电荷点位 ,粘粒矿物的晶层表面电荷起源也许起决定作用 ,此时KG 选择系数的大小顺序为 :砖红壤 >红壤 >黑土 >土 >水稻土     

土壤中植物有效硫的评价

本文综述了土壤硫素形态及有效性、土壤有效硫的测定方法以及不同方法测定的土壤有效硫与植物生长的相关性。土壤有效硫的测定主要考虑表层土壤可溶性和部分吸附态硫酸盐,但土壤有机质含量、有机硫含量和组成、土壤机械组成、pH值以及下层土壤硫素状况也是不可忽略的重要因素。目前还没有一种行之有效的统一方法能够合理评价土壤有效硫状况。今后应进一步研究不同土壤的供硫特性,并对不同有效硫评价方法进行筛选,找出适合我国土壤和气候条件下的土壤有效硫评价方法和指标,以期为合理施用含硫肥料提供依据。     

DISTRIBUTION OF SOME CHEMICAL ELEMENTS IN THE SOILS OF NORTH WEST PEMBROKESHIRE

Total amounts of Mn, Fe, Ni, Cu, Zn, As, Bt, Rb, Si, Y, Zr and Pb were determined in soil samples from approximately 250 profiles. Examples of automatically plotted maps show the distribution of some of these elements in topsoils and subsoils. Element distribution in the soils is related to land units based on underlying rock-type and air photograph interpretation; these units distinguish soils of different lithological and drainage status and many are dominated by a single soil subgroup. Agricultural and pollution aspects of the work are discussed. The survey indicates the present levels of the elements, and may be used as a comparison in future pollution studies.     

浙江省丘陵旱地土壤供钾能力的研究

浙江省主要丘陵旱地土壤的全钾量随母岩中长石和云母的含量增加而增加,幅度为0.57—3.13%,速效钾和缓效钾的含量分别为33—216ppm和80—638ppm,与土壤中高岭石及伊利石的相对含量有关。以化学试剂连续提取、电超滤(EUF)和强度/数量关系研究结果表明:高岭石为主的土壤,其缓冲容量(PBC^k)较低,有效钾数量较少,且缓效钾释放慢,在黑麦草耗竭试验中,经1—2次收获后,产量和吸钾量明显下降。以伊利石为主的土壤,其缓冲容量(PBC^k)高,黑麦草试验可得到连续的高产和吸取较多的钾。黑麦草试验还表明土壤的供钾特性较之其有效钾储量更有实践意义。     

黄土地区非代换性钾与土壤发育的关系

黄土地区土壤类型和发育程度与土壤非代换性钾有关。本文初步研究了黄土地区主要土壤类型非代换性钾的变化。影响土壤非代换性钾含量和释放累积量的主要因素是土壤质地和有机质。粉砂粒、粘粒和有机质与非代换性钾呈正相关,而砂粒与非代换性钾呈负相关。土壤非代换性钾含量由北向南从66.71-84.62增到117.09-129.95mg/100g土;释放累积量由北向南从147.03-173.00增到251.18-346.08mg/100g土。说明黄土地区土壤非代换性钾的含量和释放累积量均从北向南逐渐增加。砂绵土和黄绵土,砂黑垆土和轻黑垆土的非代换性钾含量和释放累积量其剖面分布较均一;而粘黑垆土和黑(土娄)土的粘化层的非代换性钾含量和释放累积量高于耕作层和母质层,但因地形部位不同又存有一定差异。     

辽西褐土的细粒矿物组成

辽宁省西部是低山丘陵区,年平均温度7.1℃,年平均降雨量400—500毫米,降雨集中在夏季,具有明显的大陆性气候特征,干燥度小于1,属半干旱类型.植被为油松柞木和草原灌木丛林.土壤属棕色森林土向栗钙土过渡的褐土地带.母质主要为花岗片麻岩风化物.山麓缓坡和河谷两岸为黄土丘陵.在黄土沉积物覆盖层下,常见红色风化壳露头,即红色粘土层.此外,并有松软易风化岩层,如砂岩、页岩和变质岩等.本区近百年来,由于自然植被受到严重破坏,大量水土流失,土壤侵蚀严重,土壤有机质含量低,成为辽宁省的低产区.因此,鉴定本区不同母质的土壤矿物胶体组成及其特征,不仅可以研究这一特定自然条件下土壤矿物的转化和形成,并且有助于了解土壤特性和肥力特征.