Role of the soil particle-size fractions in the sorption and desorption of potassium

The sorption and desorption capacities of two soils (a loamy soddy-podzolic soil and a sandy clay chernozem) were analyzed. Both the entire soils and their particle-size fractions were studied. Samples were taken from the soils of long-term field experiments with fertilizers. A 0.01 M CaCl₂ solution was used as the extractant. The soil fractions <10 ??m were found to have the maximum capacities for sorption-desorption of potassium. The soil fractions <0.2 ??m were the most enriched with potassium. The use of kinetic methods of analysis allowed assessing the contributions of the particle-size fractions to the potassium status of soils with different degrees of fertilization. It was noted that different fertilizing systems had no effect on the rates of potassium desorption from the colloidal fraction, while appreciable differences among the different treatments were observed for the fractions of 0.2?C1.0 and 1?C10 ??m.     

化肥对黑土不同粒级碳水化合物的影响

本文采集公主岭市长期定位监测基地不施肥和施用不同化肥的黑土,通过超声波分散-离心分离得到细黏粒(<0.2μm)、粗黏粒(0.2～2μm)、粉粒(2～53μm)、细砂粒(53～250μm)、粗砂粒(250～2000μm)5个颗粒级别,分析全土及不同粒级中土壤碳水化合物并进行含量与分布的比较。结果表明,黑土中不同粒级碳水化合物库的性质差异显著,碳水化合物多集中在粉+黏粒中;长期施用化肥后,黑土全土及各粒级碳水化合物库大小和浓度基本上没有变化;粗砂粒级(Gal+Man)(:Ara+Xyl)下降,表明该粒级中植物来源碳水化合物所占比重有所增加,暗示出粗砂粒级对施肥措施更为敏感。     

小麦分泌的有机酸影响钙质土中锌的释放

Rhizosphere drives plant uptake of sparingly soluble soil zinc(Zn).An investigation with three experiments was conducted to study organic acid exudation by two contrasting wheat genotypes(Sehar-06 and Vatan),Zn fractions in 10 different calcareous soils from Punjab,Pakistan,and release of different soil Zn fractions by organic acids.The two genotypes differed significantly in biomass production and Zn accumulation under deficient and optimum Zn levels in nutrient solution.At a deficient Zn level,Sehar-06 released more maleic acid in the rhizosphere than Vatan.Ten soils used in the present study had very different physicochemical properties;their total Zn and Zn distribution among different fractions varied significantly.Zinc release behaviour was determined by extracting the soils with 0.005 mol L-1 citric acid or maleic acid.The parabolic diffusion model best described Zn release as a function of time.Parabolic diffusion model fitting indicated more maleic acid-driven than citric acid-driven soil Zn mobility from different fractions.Cumulative Zn release in six consecutive extractions during 24 h ranged from 1.85 to 13.58 mg kg-1 using maleic acid and from 0.37 to 11.84 mg kg-1 using citric acid.In the selected calcareous soils,the results of stepwise linear regression indicated significant release of Fe-Mn oxide-bounded soil Zn by maleic acid and its availability to the Zn-effcient genotype.Hence,release of maleic acid by plants roots played an important role in phytoavailability of Zn from calcareous soils.     

Potassium and magnesium in some Kenyan soils: their mineral sources and release to Ca-resin

Five soil types from Kenya were examined for their ability to release K and Mg to crops by extracting them with a calcium-saturated cation exchange resin, and for the mineral sources of K and Mg. Amounts and rates of release of exchangeable, short- and long-term reserves of K and Mg were determined. This was done for K before and after one, two and 10 wetting and drying (WD) cycles, designed to mimic the effect of the local climate on K release. The order of decreasing K and Mg contents of the soils was Muguga > > Katumani > Kampi-ya-Mawe (KYM) ∼ Ithookwe ∼ Kwale. In the case of K, wetting and drying increased the exchangeable fraction in all of the soils. The Muguga, Ithookwe and KYM soils have the capacity to release a great deal of K in the long-term, but at very different rates; the Kwale soil has few reserves and fixes K on WD.
The K and Mg contents of the soils were closely related to the mica contents of the clay + silt fractions. Exchangeable and non-exchangeable K was released from soil micas primarily by ion exchange, with some contribution to non-exchangeable K from dissolution. Release of exchangeable Mg was primarily by ion exchange, whilst that of non-exchangeable matrix Mg was by dissolution of trioctahedral mica in the clay + silt and the sand fractions of the soils. Response would be expected only to K fertilizers and only with the Kwale soil. However, all the other soils should, in the interests of good husbandry, receive maintenance dressings of K and Mg at convenient times in the crop rotation.     

不同浓度螯合剂和浸提时间对土壤磷素提取效果研究

为确定螯合剂活化土壤磷素的最佳浓度和最优浸提时间,参考水肥一体化技术,在室内浸提条件下,研究了不同浓度(0,0.05,0.1,0.25,0.5,1.0g/L)乙二胺四乙酸(EDTA)和柠檬酸螯合剂(pH=4)在不同浸提时间(1,12,24,48,72h)下对粮田、菜田土壤和有效磷被钝化后菜田土壤中磷素提取效果。结果表明:EDTA和柠檬酸在粮田土壤上对磷素提取中最佳条件为螯合剂浓度0.05g/L,浸提时间12h。EDTA和柠檬酸在菜田土壤、明矾钝化和混合钝化(明矾∶白云石为1∶1)菜田土壤上提取磷素的最佳条件为螯合剂浓度0.5g/L,浸提时间12h;而在白云石钝化土壤中则为螯合剂浓度0.5g/L,浸提时间1h。总体来看,柠檬酸的活化提取磷素效果优于EDTA,尤其是在采用明矾和白云石钝化的土壤上。     

华北山前平原农田土壤养分循环的酶学调控

土壤酶是推动土壤养分循环的生物催化剂, 研究华北山前平原农田养分循环的酶学调控机制将有助于评价该地区土壤养分状况。试验用土壤取自中国科学院栾城农业生态系统试验站, 分析了土壤脲酶与碱性磷酸酶活性在0~10 cm、10~20 cm、20~30 cm 和30~40 cm 4 个土层中的分布, 研究了土壤粗砂(2 000~200 μm)、粉砂(200~63 μm)、粉粒(63~2 μm)和黏粒(2~0.1 μm) 4 个颗粒组中土壤酶活性与土壤养分之间的相关性。研究结果表明: 土壤脲酶活性与碱性磷酸酶活性均随土壤深度增加而降低, 土壤酶活性随土壤粒径减小而升高。在土壤粗砂和粉砂组分中, 土壤酶活性与养分含量显著相关, 而在土壤粉粒和黏粒组分中, 土壤酶活性与土壤养分含量并不总是显著相关。这些结果说明: 土壤酶活性在土壤养分循环中起到重要的调控作用, 土壤粗砂和粉砂中的土壤酶具有较高的田间实际催化活性, 对土壤养分循环的贡献较大; 与此相反, 土壤粉粒和黏粒中的土壤酶由于土壤无机矿物的吸附作用而失去部分田间催化能力, 降低了其对土壤养分循环的贡献。     

长期施肥对旱地红壤团聚体磷素固持与释放能力的影响

在中国科学院红壤生态试验站26年的旱地红壤长期肥料定位试验中,选取无机肥试验区的NPK、NK处理,有机无机肥配施试验区的对照(CK)、CK+稻秆(RS)、CK+花生秸秆还田(PS)、CK+绿肥(FR)及CK+猪厩肥(PM)等7个肥料处理土壤,采用湿筛法逐级提取并得到粒级依次为2 mm、2~1 mm、1~0.25 mm与0.25~0.053 mm的团聚体土壤样品;通过室内分析获得了土壤及各粒级团聚体的全磷(TP)、有效磷(Available P)、水溶性磷(CaCl_2-P)、土壤磷素吸持指数(PSI)及土壤磷素饱和度(DPS)等指标值,并探讨了上述测定指标间的相关关系。结果表明:长期施用磷肥可有效保持旱地红壤的供磷水平,配施猪厩肥可显著增加旱地红壤及大小团聚体的TP、有效磷及CaCl_2-P含量、降低土壤PSI并显著增大旱地红壤DPS,加大了旱地红壤磷素的流失风险;随着土壤中1 mm粒级团聚体数量的增多,旱地红壤磷素储量显著增加,磷素固持能力显著下降,土壤磷释放潜能随之增大。由DPS、有效磷及CaCl_2-P的分段线性拟合方程可以推断得出,当旱地红壤中有效磷为168~260 mg kg~(-1)时或DPS28%,土壤磷素具有潜在流失风险;当有效磷≥260 mg kg~(-1)或DPS≥28%,土壤磷素具有极高的流失风险,应立即停止施用磷肥尤其是有机磷肥,并重新调整施肥方案,以避免土壤磷素流失及其对水体环境的污染。     

几种包膜缓控释肥粒养分释放特征的研究

采用水浸泡法对国内外4种包膜控释肥料的养分释放特性进行了系统的研究。结果表明,4种缓控释肥料的初期溶出率均小于12%,微分溶出率在0.4%～1.5%之间,这符合国际上公认的缓/控释肥的评价标准,初期溶出率小于15%、微分溶出率在0.25%～2.5%之间。采用水浸泡法测定包膜控释肥料养分释放特征,简便快速,检测时间短,重复次数少,养分浓度变化直接反映出包膜控释肥料的释放速率特性,还可以定量的测定其供肥性能,控释肥料有控制养分释放、延长供应时间的作用;其中腐殖酸和炭基有利于提高肥料颗粒的水稳定性,减缓养分的释放速率。     

包膜控释肥料养分释放率快速测定方法的研究

包膜控释肥料养分释放率的快速测定是控释肥质量检测和制定评价标准的关键。快速测定方法可以在较短时间内,推测和评价控释肥料的养分释放速率的快慢及释放期的长短。本研究对4种不同包膜控释肥料在25℃温度条件下的静水释放过程进行了测定,并应用100℃快速浸提化学实测法的测定结果与之拟合,找出两者相同养分释放量的时间对应关系方程,并对方程进行了检验和评价;同时,还对100℃温度条件下快速浸提液进行了电导率法(简便方法)的测定。结果表明,4种不同包膜控释肥料的相同养分释放量与时间对应关系方程的拟合度均达到极显著水平;在100℃温度条件下,快速浸提测定法能在较短的时间内准确测定包膜控释肥料的养分释放率,释放期为36～个月的包膜控释肥,在104～8.h就可初步测定出养分释放期;在25℃释放期为6个月的控释肥,100℃快速浸提测定的养分释放期的最大误差为10.d(5.6%);100℃快速浸提电导率法亦可简便快速的测定出包膜控释肥的养分释放率,其对养分释放期为6个月的包膜控释肥料预测值的最大误差为15.d(8.3%)。     

砂质土壤磷素的组成特点与释放规律研究

砂质土壤磷素主要以可提取态形式积累,有很高的释放潜力。该类土壤磷素的释放受土壤pH、土水作用时间和土壤溶液化学组成等的影响。土壤酸化、土壤溶液中Na+浓度的提高及土壤与水的作用时间增加可促进土壤磷素的释放。用淋洗方法和平衡提取等2种方法对土壤磷素的释放评价表明,淋洗方法测得的P量较小,可代表土壤短期内P释放强度;而平衡提取法提取的P数量较大,可代表土壤P长期释放的容量。     

长期酸化对红壤中活性固相铝库大小及亏损程度的影响

用连续分级提取和反复多次酸提取方法研究了长期土壤酸化对红壤固相铝库中铝含量及亏损程度的影响。研究结果表明:嵊县红壤的活性铝库大于永春红壤和屯溪红壤;因永春红壤和屯溪红壤的酸化程度大于嵊县红壤,前两者的有机铝库和无机铝库都比嵊县红壤的亏损,因此反复酸提取过程中铝的释放量也比嵊县红壤少;当高强度酸输入土壤后,弱键合的有机络合态铝可快速活化并亏损,剩余铝库因活性小而释放速率减小,但长期酸化过程中,动力学控制的低活性铝库的活化可能对铝的溶解量仍有重要贡献。     

不同浸提条件对包膜控/缓释肥水中溶出率的影响

以几种不同包膜材料控／缓释肥为供试肥料,研究不同肥(养分)水比、浸提方式(连续浸提和更换浸提液)、温度和pH条件对控／缓释肥水中溶出率的影响。结果表明,浸提液中肥料浓度是影响养分释放的重要因素,加大肥水比、更换浸提液可以显著减小这种影响。升高温度,有机和无机材料包膜控／缓释肥水中溶出率均显著加快。肥料类型、肥水比对浸提液的pH都有显著影响,但在连续浸提和更换浸提液方式下,7d内浸提液的pH有着不同的变化趋势。控／缓释肥在pH.5的磷酸盐缓冲液中的溶出率显著高于在pH.7的磷酸盐缓冲液中的溶出率。因此,对于不同包膜材料控／缓释肥以一定pH值的微酸性缓冲溶液作为浸提剂,定期更换浸提液或采用动态流法,相同的氮(或磷、钾)水比,30℃左右的浸提条件是较为合理的。     

Base cation,aluminum, and phosphorus release potential in Danish forest soils

Long‐term nutrient supply in forest ecosystems is due to the dissolution of primary and secondary minerals in soils. The potential of nutrient release in 19 forest soils in a cool humid climate was examined. The soil profiles are classified as Alfisols (10), Spodosols (2), Entisols (4), Ultisols (1), and Mollisols (2), thus covering a gradient in soil fertility. Short‐term and long‐term release of calcium, magnesium, potassium, phosphorus, and aluminum was evaluated by a batch extraction using dilute nitric acid (0.1 M) for 2 hours, followed by 2 days (48 h), and 7 days (168 h). The solution was renewed after 2 and 50 hours extraction time. Nutrient pools expressed as g m^–2 to soil depth 100 cm, and a base index (Ca²⁺+ Mg²⁺+ K⁺ (mol_c m^–2) : Ca²⁺ + Mg²⁺ + K⁺ + Al³⁺ (mol_c m^–2)) were interpreted in relation to soil texture classes. Subsoil texture classes: Coarse: < 5 % clay; medium 5–10 % clay or (> 5 % silt or > 50 % fine sand), or fine > 10 % clay were evaluated as an indicator of forest soil quality. Base cation and phosphorus release decreased in the order fine > medium > coarse. Texture classes explained base cation release by about 80 % of total variation, and phosphorus release by 40–50 %. The base index generally increased by extraction time for sandy soils and decreased for loamy soils. This indicated that sandy soils released accumulated reactive aluminum in the 0–2 hour extraction. Subsoil texture class is suggested as a pedotransfer function for long‐term nutrient release potential in Danish forest soils.     

磷矿粉在酸性土壤中的施用: 比较磷酸盐提取方法测定磷矿粉溶解程度

Three phosphate extraction methods were used to investigate the dissolution,availability and transfo-mation of Kunyang phosphate rock(KPR) in two surface acid soils.Dissolution was determined by measuring the increase in the amounts of soluble and adsorbed inorganic phosphate fractions,and did not differ signifi-cantly among the three methods.Significant correlations were obtained among P fractions got by the three extraction methods.Dissolution continued until the end of the 90-day incubation period.At the end of the period,much of the applied phosphate recovered in both soils were in the Al- and Fe-P or in the hydroxide-and bicarbonate-extractable inorganic P fractions.The dissolution of KPR in the two soils was also similar: increased addition of phosphate rock resulted in decreased dissolution.The similarity in the order and extent of dissolution in the two soils was probably due to the similarity in each soil of several factors that are known to influence phosphate rock dissolution,namely low CEC,pH,P level,and base status;and high clay and free iron and aluminum oxide contents.The results suggested that KPR could be an aternative P source in the soils are not limiting.     

高温-超低温处理对控释肥氮素释放特性的影响

采用水培和土培方法,探讨了2种组合的高温-超低温处理对MEISTER 180氮素释放特性的影响。结果表明,55℃处理期平均养分溶出率（η△t）为6.6%~8.9%;超低温处理期平均养分溶出率（η△t）为0.1%~0.6%。高温-超低温处理后MEISTER 180水中和土中氮素释放均呈直线型模式,相关系数R2在0.8552~0.9505之间;水中和土中养分溶出率比值变动范围在1.0~1.3之间,表明氮素释放受水分影响小,高温-超低温处理未改变MEISTER 180释放模式。     

Kinetics of Iron and Manganese Release from Contaminated Calcareous Soils

Knowledge of the release of heavy metals (HM) and their chemical speciation is necessary for characterizing HM behavior in soils. The kinetics and characteristics of iron (Fe) and manganese (Mn) release were studied in 10 contaminated calcareous soils using 0.01 M calcium chloride (CaCl₂), 0.01 M ethylenediamine tetraacetic acid (EDTA), and 0.01 M malic acid (malic acid) extractions. Iron and Mn in soil samples were fractionated before and after 2084 h kinetic release using a sequential extraction procedure. The proportion of Fe and Mn released by EDTA was greater than that with CaCl₂ and malic acid. A power model satisfactorily described Fe and Mn release from soils. In general, the mean release rate of Fe was greater than that of Mn, indicating a greater rate of Fe release from contaminated soils. It was shown that Fe and Mn distributions were similar in native soils and they were mainly found in Fe-Mn oxides and organic-matter (OM) fractions. There were changes in the proportional distribution of Fe and Mn in all soils during the 2084 h kinetic study with different extraction solutions. In general, the proportions of Fe and Mn associated with carbonate (CARB) and OM fractions tended to decrease, with corresponding increases in the Fe-Mn oxides for Mn and residual (RES) fractions for Fe during the kinetic study with all extraction solutions. The Fe and Mn solubility at the initial and final stages of release was controlled by siderite (FeCO₃), vivianite [(Fe)₃(PO₄)₂·8H₂O], MnCO₃(am), MnHPO₄, and rhodochrosite (MnCO₃) minerals in all extraction solutions. Based on a risk assessment and percentage of release of metals, there is a high potential for Mn release into the food chain from contaminated soils.     

长期施肥对浙江稻田土壤团聚体及其有机碳分布的影响

以浙江省稻田长期定位试验站为依托,研究长期不同施肥措施对土壤团聚体及其有机碳分布的影响。研究结果表明,与不施肥对照(CK)相比,栏肥与化肥配施(NPKOM)、单施栏肥(OM)、秸秆与化肥配施(NPKRS)和单施秸秆(RS)处理均显著提高了2 mm和2~0.25 mm水稳定性大团聚体的含量和团聚体平均重量直径(p0.05),强化了团聚体对土壤有机碳的物理保护作用。此外,长期有机无机配施(NPKOM和NPKRS)处理显著提高了各个粒级团聚体中有机碳含量,并且显著增加水稳定性大团聚体有机碳的贡献率,而长期单施化肥和单施秸秆处理并未有效增加土壤总有机碳含量。不同施肥处理下,2~0.25 mm粒级团聚体有机碳占土壤总有机碳的34.2%~48.6%,是土壤有机碳的主要载体。利用傅立叶变换红外光谱(FT-IR)技术对2~0.25 mm和0.053 mm团聚体进行结构表征,发现长期单施有机肥或者有机无机配施下芳香族C较CK提高29.9%~45.2%,较NPK处理提高22.3%~36.6%,提高了土壤有机碳的芳构化。在有机碳积累方面,施用有机肥,尤其是栏肥与化肥配施,同时强化了团聚体对有机碳的物理保护以及促进了化学抗性有机碳组分的积累,是加强稻田土壤有机碳库积累的合理施肥模式。     

The contribution from hyphae, roots and organic carbon constituents to the aggregation of a sandy loam under long-term clover-based and grass pastures

Water-stable macro-aggregate size fractions (>2.0 mm, 1.0–2.0 mm, 0.5–1.0 mm and 0.25–0.5 mm) and non-aggregated soil from a sandy loam under long-term clover-based pasture and from grass pasture were analysed to determine the role of acid- and water-extractable carbohydrate C, total hyphal length, microbial biomass, organic C and total and mycorrhizal root length in stabilization of the aggregates. Aggregates were examined by scanning electron microscopy (SEM) and the particle-size distribution of the size fractions was also determined. Macro-aggregation increased under grass, relative to clover-based pasture; however, the properties of the aggregate fractions measured did not reflect this difference. Microbial-biomass C, extractable-carbohydrate C, hyphal length, total and mycorrhizal root length and organic C content of the soils were poorly correlated with macro-aggregation. Within the aggregates, the proportion of 250–1000-km sand was smaller and clay, silt and fine sand (20–250 μm) were greater relative to non-aggregated soil, suggesting that the >250-μm sand in the non-aggregated soil limited the stabilization of macro-aggregates. Under SEM, no enmeshment of aggregates by hyphae and roots was apparent. Although 50–160 m hyphae g^?1 soil was found within the aggregates, calculations showed that on average only 5 to 13 lengths of hyphae were associated with each 250-μm cube of soil within the aggregates, and suggested little potential to stabilize the aggregates by enmeshing. On average, all >2.0-mm aggregates contained less than 3.6 mm of roots and less than 50% by weight of <2.0-mm aggregates contained a single length of root. The findings cast doubt about the role of hyphae and fine roots in the stabilization of macro-aggregates through an enmeshing mechanism in sandy soils.     

包膜尿素养分释放特性测定方法的研究

分别以水、砂子、热硼酸溶液为介质,研究不同浸提方式对缓/控释肥养分溶出率的影响及两种缓/控释肥料的溶出特征。结果表明,同一种肥料在不同的介质中溶出率趋势无显著差异,以热硼酸溶液为介质,可提高检验速度,是检验长释放期控/缓释肥料产品质量的有效方法。     

Data transformations between soil texture schemes

Various soil texture schemes are in current use. These differ in the size ranges of their particle fractions. There is a need to establish simple methods to correlate these conventional schemes. Therefore I have defined closed-form exponential and power law functions to fit models to cumulative particle-size distribution data. I have tested the functions for their suitability (i) to represent cumulative particle-size distribution curves and (ii) to transfer data between distributions that differ in the size ranges of the particle fractions. I found that closed-form exponential functions adequately represent the cumulative particle-size distributions of fine-textured soils (clay, silty clay, silty clay loam, clay loam, silt loam and loam texture), whilst closed-form power functions better describe the cumulative particle-size distributions of coarse-textured soils (sand, loamy sand, sandy loam, sandy clay and sandy clay loam texture). The functions defined are found to be suitable to transfer data between different texture schemes. The use of this approach is illustrated by examples of data transformations between three widely used soil texture schemes: ISSS, Katschinski's and USDA.