鄂、湘两省土地土壤粘粒矿物的研究——Ⅱ.莽山北坡土壤中的粘粒矿物

对莽山北坡不同海拔高度的5个土壤剖面15个土样的粘粒矿物进行了X射线衍射分析和粘粒氧化物的化学选择溶提测试,结果表明:(1)莽山土壤中粘粒矿物组合的垂直变化明显。海拔500m以下的红壤、黄红壤的粘土矿物以1:1型高岭为主,粘粒氧化物中有较多的晶质氧化铁和热碱溶性氧化硅。海拔850m以上的黄壤、暗黄棕壤和山地灌丛草甸土的粘土矿物以2:1型的14×10^-10m过渡矿物和水云母为主,粘粒氧化物中有较多的无定形氧化铁、铝和三水铝石。(2)随海拔升高,土壤粘粒的硅铝率、氧化铁的游离度变幅不大,而氧化铁的活化度和各种氧化铝的富集明显提高。根据这些结果,结合莽山土壤的风化威土的条件与过程,讨论了莽山垂直带土壤中粘土矿物和氧化物的分布与演化过程的特点。     

不同质地小麦根际土壤有机碳、氮含量及特性研究

测定了两种不同质地土壤小麦根际土及非根际土中不同形态有机碳、氮的含量及特性。结果表明,粘壤土及砂质壤土两种不同质地土壤小麦根际土中有机碳、可溶性有机碳(WEOC),土壤全氮、可溶性有机氮(WEON)、游离氨基酸及硝态氮和铵态氮均显著高于非根际土;根际土及非根际土中WEON的含量均高于硝态氮及铵态氮含量,其在根-土界面氮素转化中的作用值得关注。不同质地土壤相比,粘壤土中各指标的含量均显著高于砂质壤土。根际土有机碳矿化累积量及矿化率均高于非根际土;培养期间粘壤土释放的CO2量明显低于沙质壤土,这可能与粘壤土粘粒含量高,对土壤有机碳的保护作用有关。     

长期不同施肥对土壤各粒级组分中氮含量及分配比例的影响

土壤培肥过程中氮素的积累和在各级土壤颗粒中的分配对了解土壤氮素积累机制和氮素的可持续管理具有重要意义。本研究以红壤旱地长期定位试验为基础,采用离心法分离土壤颗粒,通过分析氮素在土壤不同颗粒中的含量,研究长期施肥对土壤中不同粒级土壤氮的分配的影响。结果表明,施肥二十年后,在020 cm土层,施肥处理的全氮含量在1.19~1.98 g/kg 之间,施肥处理全氮含量显著高于不施肥处理（CK）。在2040 cm土层,土壤全氮含量分布在0.59~0.84 g/kg之间,显著低于表层土壤氮含量; 在020 cm土层,与氮磷钾化肥配施处理（NPK）相比,单施或者配施有机肥的土壤与砂粒、 粗粉粒、 细粉粒、 粘粒结合的氮含量分别提高220%、 84%、 46%和26%。而在2040 cm土层,与NPK处理相比,有机肥的施用仅提高了与细粉粒、 粘粒结合的氮含量,降低了与粗粉粒结合的氮含量; 在020 cm土层中,红壤氮素主要分布在粘粒中。2040 cm土层CK、 NPK和氮磷钾配施加秸秆还田处理（NPKS）表现为与粗粉粒结合的氮的分配比例最高,而施用有机肥的处理氮素分布仍以粘粒占比例最高。相关分析表明,土壤表层＜5 m粒级的土壤颗粒中氮含量和作物的经济产量呈显著性正相关。长期施用有机肥可以显著提高表层土壤全氮及与各个颗粒结合氮的含量,不同处理的氮主要保存在粘粒中。而亚表层土壤中,施化肥或者秸秆还田加速了粘粒结合态氮的耗竭,配施有机肥促进了氮在粘粒中的积累,也更有利于土壤全氮的积累,是可持续的氮素管理措施。     

土壤质地对间歇入渗减渗效果的影响

以室内不同质地土壤连续和间歇入渗对比试验为依据,以土壤粒径小于０．００２ｍｍ的粘粒含量的质量百分数为反映土壤质地的物理量,分析讨论了土壤质地对间歇入渗减渗效果的影响。研究结果表明,土壤质地是影响土壤间歇入渗减渗效果的主要因素之一;随着土壤粘粒含量的增加,土壤间歇入渗相对减渗率增加;绝对减渗量以土壤粘粒含量为１３％时为最大;当土壤粘粒含量小于１３％时,随着土壤粘粒含量的增加,绝对减渗量增加;当土壤粘粒含量大于１３％时,随着土壤粘粒含量的增加,绝对减渗量急剧减小。     

华北黄泛平原潮土土壤养分与土壤粒级的关系研究

根据第二次全国土壤普查资料,利用数理统计的方法研究了华北黄泛平原潮土土壤粒级与土壤养分含量之间的关系。研究结果表明,土壤耕层养分含量与土壤砂粒成负相关,与小于0.01 mm的各粒级成正相关。其中土壤有机质含量主要受砂粒(1~0.05 mm)和细粘粒(<0.001 mm)含量的影响,土壤全氮含量主要受细粘粒含量的影响,土壤全磷含量主要受砂粒和粗粉粒(0.05~0.01 mm)含量的影响,土壤速效磷含量主要受细粘粒含量的影响,土壤速效钾含量主要受细粉粒(0.01~0.005 mm)含量的影响。     

土壤质地对间歇人渗减渗效果的影响

以室内不同质地土壤连续和间歇入渗对比试验为依据,以土壤粒径小于０．００２ｍｍ的粘土粒含量的质量百分数为反映土壤质地的物理量,分析了讨论了土壤质地间歇入渗减渗效果的影响。研究结果表明,土壤质地影响土壤间歇入渗减渗效果的主要因素之一,随着土壤粘粒含量的增加,土壤间歇入渗相对减渗率增加,绝对减渗量以土壤粘粒含量为１３％时为最大,当土壤粘粒含量小于１３％时,随着土壤粘粒含量的增加,绝对减渗量增加,当土壤适     

粘土矿物与肥料的相互作用及其应用途径的研究

本文采用了上种不同类型的粘土矿物，在粘和量和肥料配方相同的条件下，研究了粘土矿物的原土及其改性粘土与肥料的相互作用对复混肥成粒率和养分释放的影响，结果表明，各种粘土矿物历期 组成，结构和性质各异，对复混肥的团聚作用有明显的影响。采用亲水性的表面活性剂１和疏水性的表面活性剂２号使粘土改性，不仅能强化复混肥的团聚作用，且能有效地控制其养分的释放，尤其是表面活性剂号能使养分的释放具有明显的缓解作用。     

蒙山茶园土壤组分对铝吸附解吸热力学特征的影响

采用间歇法和振荡平衡法,通过实验室模拟,研究了蒙山茶园土壤(紫色土和黄壤)原土及各粒级组分对铝吸附解吸的热力学特征,并分析土壤有机质、游离氧化铁和CEC对其吸附解吸的影响。结果表明:(1)不同土壤原土及各粒级组分对铝的吸附量都随铝离子浓度的增大而增加,且各粒级土壤对铝的吸附量不同,表现为土壤颗粒比表面越大,有机质、游离氧化铁和CEC越高,其吸附量越大。紫色土原土及各粒级组分对铝的等温吸附过程用Freundlich方程描述最佳,说明紫色土对铝的吸附是多层吸附;而黄壤原土及各粒级组分对铝的等温吸附过程则用Langmuir方程描述最佳,说明黄壤对铝的吸附以单层吸附为主。(2)紫色土原土及各粒级组分对铝的解吸率表现出以下关系:粗砂粒原土细砂粒粉粒粘粒,黄壤原土及各粒级组分对铝的解吸率则表现出以下关系:细砂粒粗砂粒原土粉粒粘粒,两者解吸率的大小关系均与其有机质及游离氧化铁相反,表明两种土壤的原土及各粒级组分中有机质和游离氧化铁越高,其专性吸附率就越高,从而解吸率越小,说明土壤有机质和游离氧化铁影响土壤对铝的固持能力。(3)土壤最大吸附量与有机质、游离氧化铁含量和CEC都表现出显著或极显著的正相关关系,而其最大解吸率也均与有机质、游离氧化铁含量和CEC表现出显著或极显著的负相关关系。     

接种蚯蚓对土壤团聚体分布、稳定性及有机碳赋存的影响

通过一个月的室内培养试验,研究在不同土壤与植物残体施用下接种蚯蚓对土壤团聚体分布、稳定性及土壤有机碳的影响。供试土壤为粘粒含量较低的潮土(86 g/kg)与粘粒含量较高的红壤(318 g/kg),试验前受试土壤的大团聚体全部人为破坏;供试植物残体为高碳氮比的玉米秸秆与低碳氮比的三叶草残体;供试蚯蚓为威廉腔环蚓(Metaphire guillelmi)。试验结果表明:不同土壤与植物残体施用下,蚯蚓对土壤水稳性团聚体分布、微团聚体分散性及土壤有机碳赋存的作用不同,潮土中施用两种植物残体时,接种蚯蚓均显著降低土壤粘粒分散率(P0.05),但不对水稳性团聚体分布及团聚体平均重量直径(MWD)产生影响,同时赋存于粘粉粒中的有机碳含量均增加;红壤中施用两种植物残体时,接种蚯蚓均显著降低土壤粘粒及粘粉粒分散率(P0.05),同时均形成2 mm大团聚体,2～0.25 mm大团聚体所占比例及MWD也显著增加(P0.05),相应赋存于2 mm大团聚体与2～0.25 mm大团聚体中的土壤有机碳含量均显著增加(P0.05)。两种土壤在施用植物残体且接种蚯蚓时均可显著增加土壤有机碳的含量(P0.05)。对于水土流失和土壤结构严重退化的地区,通过施用植物残体并接种蚯蚓是恢复土壤结构与增加土壤有机碳储存的重要生态工程措施。     

贵州典型山银花土壤机械组成与养分特性及其关系

采用比重计法测定土壤机械组成,分别采用电位测定法、凯氏定氮法、碱解扩散法、碳酸氢钠浸提钼蓝比色法、重铬酸钾外加热法、醋酸铵浸提-火焰光度法测定土壤pH、全氮、碱解氮、有效磷、有机质及速效钾,以非根区土壤为对照,对贵州典型山银花土壤机械组成与土壤肥力特性及它们之间的关系进行研究。结果表明:根区颗粒组成分为粗粉粒细砂粒粘粒细粉粒≈中粉粒≈粗砂粒;非根区颗粒组成顺序为粗粉粒粘粒细粉粒≈中粉粒细砂粒≈粗砂粒,表明非根区质地较根区粘重。根区粘粒、粉粒和物理性粘粒含量小于非根区,砂粒含量较高;根区与非根区各土壤类型大小顺序分别为黄壤紫色土≥石灰土;黄壤石灰土紫色土。贵州产区根区养分含量高于非根区,土壤养分水平均在Ⅱ级以上,非根区土壤养分含量均在Ⅲ级以上水平,根区砂粒含量与有机质、pH、速效钾、有效磷、全氮含量呈正相关;粉粒含量与pH、有机质、全氮、速效钾含量均呈负相关;粘粒含量与有机质、pH、全氮含量均呈负相关;物理性粘粒含量与有机质、pH、全氮、速效钾含量均呈负相关。非根区砂粒含量与有机质、碱解氮、全氮含量均呈负相关,与pH、有效磷含量均呈正相关;粉粒含量与pH、碱解氮含量均呈正相关,与速效钾含量呈负相关;粘粒含量与所有指标呈负相关;物理性粘粒含量与pH呈极显著负相关。得出山银花根系对改善土壤粘重质地有较好作用;质地粘重的土壤,机械组成含量对山银花生长的影响较大,且砂粒含量越高对山银花生长的促进作用越明显。     

旱地土壤的供氮潜力

对潮土、黄褐土、黄棕壤和红壤旱地的供氮潜力进行研究的结果表明,矿化势(No)变化于60340mgkg-1之间,矿化速率常数(K)0.00556-0,01280d-1,矿化势(No)、矿化速率常数(K)和矿化量(Nt)与土壤供氮量均呈显著相关,说明No、Nt和K是土壤供氮潜力的重要参数。这些参数与土壤全氮、有机质、有机氮、易分解有机质、C/N等土壤组成性质密切相关。测定表明,供试土壤粘土矿物多以2:1型为主,土壤固定态铵多在100mgkg-1以上,有部分可重新释放出来,是研究土壤供氮潜力时不容忽视的因素。     

Effect of grinding on the decomposition of soil organic matter—I. The mineralization of organic nitrogen in relation to soil type

The effect of grinding on aerobic nitrogen mineralization in ten soils of widely different properties was studied. The aerobic mineralization of nitrogen was increased in seven of ten soils when they were ground to < 0.18 mm and < 0.05 mm; these seven soils contained more clay than the other three soils. Five soils with montmorillonite clay showed larger proportional increases in mineralization due to grinding than did the two soils with kaolin clay. The implications of these findings are discussed in terms of the inability of some previous workers to find increases in the rate of organic matter decomposition when soils are physically disrupted and the importance of clay protection in the resistance of soil organic matter to decomposition.     

Studies of nitrogen immobilization and mineralization in calcareous soils—II: Mineralization of immobilized nitrogen from soil fractions of different particle size and density

¹⁵NO^?₃ was immobilized in a calcareous sandy soil and a calcareous clay soil each incubated with glucose and wheat straw. Net mineralization of organic-¹⁵N was more rapid in the sandy soil, irrespective of C amendment, and in soils amended with glucose. Intermittent drying and wetting of soils during incubation stimulated mineralization of ¹⁵N-labelled and native soil organic-N in all treatments. The availability (percentage mineralization) of recently-immobilized ¹⁵N consistently exceeded that of the native soil N. Ratios of the availability of labelled and unlabelled N were similar in the sandy and clay soils but varied according to C amendment, drying and wetting cycle and incubation period.Changes in the distribution of immobilized N amongst soil extracts and soil fractions of different particle size and density were determined during periods of net N mineralization. In straw-amended soils, the organic-¹⁵N of a light fraction, sp.gr. < 1.59, decomposed relatively rapidly during the late mineralization period. Decreases of organic ¹⁵N of the fine clay fraction were also recorded. In glucose-amended soils, net N mineralization was accompanied by significant decreases in the concentrations of organic-¹⁵N of the silt and fine clay fractions.Drying and rewetting of soils hastened or magnified changes occurring in the organic-¹⁵N of soil fractions, but qualitatively, the pattern of change was similar to that observed with soils incubated under uniformly-moist conditions.The percentage distribution of labelled and unlabelled N suggested that in the long term, the silt fraction will accumulate an increasing proportion of the more stable nitrogenous residues.     

Organic carbon mineralization responses to temperature increases in subtropical paddy soils

Purpose

Understanding organic carbon mineralization and its temperature response in subtropical paddy soils is important for the regional carbon balance. There is a growing interest in factors controlling soil organic carbon (SOC) mineralization because of the potential for climate change. This study aims to test the hypothesis that soil clay content impedes SOC mineralization in subtropical paddy soils.

Materials and methods

A 160-day laboratory incubation at temperatures from 10 to 30 °C and 90% water content was conducted to examine the dynamics of SOC mineralization and its temperature response in three subtropical paddy soils with different clay contents (sandy loam, clay loam, and silty clay soils). A three-pool SOC model (active, slow, and resistant) was used to fit SOC mineralization.

Results and discussion

Total CO₂ evolved during incubation following the order of clay loam > silty clay > sandy loam. The temperature response coefficients (Q ₁₀) were 1.92?±?0.39, 2.36?±?0.22, and 2.10?±?0.70, respectively, for the sandy loam soil, clay loam soil, and silty clay soil. But the soil clay content followed the order of silty clay > clay loam > sandy loam. The sandy loam soil neither released larger amounts of CO₂ nor showed higher temperature sensitivity, as expected, even though it contains lower soil clay content among the three soils. It seems that soil clay content did not have a dominant effect which results in the difference in SOC mineralization and its temperature response in the selected three paddy soils. However, dissolved organic carbon (DOC; representing substrate availability) had a great effect. The size of the active C pool ranged from 0.11 to 3.55% of initial SOC, and it increased with increasing temperature. The silty clay soil had the smallest active C pool (1.40%) and the largest Q ₁₀ value (6.33) in the active C pool as compared with the other two soils. The mineralizable SOC protected in the silty clay soil, therefore, had even greater temperature sensitivity than the other two soils that had less SOC stabilization.

Conclusions

Our study suggests that SOC mineralization and its temperature response in subtropical paddy soils were probably not dominantly controlled by soil clay content, but the substrate availability (represented as DOC) and the specific stabilization mechanisms of SOC may have great effects.     

不同施肥措施对稻田土壤氮矿化的影响

采集田间通过不同施肥处理的水稻土为研究对象,在室内采用淹水培养方法,研究不同施肥措施对水稻土氮矿化的影响。结果表明:与不施肥处理相比,施加氮肥和饼肥能提高土壤的氮矿化能力;与常规施氮处理相比,采用新型施肥措施,氮肥+木质素、一次施用的水稻缓释肥、氮肥+有机碳源均降低土壤的氮矿化作用,其中氮肥+有机碳源处理与常规施氮处理相比,土壤全氮增加了16.7%,但淹水培养期间土壤的氮矿化量却减少了18.5%,这一结果说明,采用这些新型施肥措施有利于增加土壤对氮的固持,降低氮素向环境损失的风险。     

Effects of the phenylamide fungicides, mefenoxam and metalaxyl, on the microbiological properties of a sandy loam and a sandy clay soil

The objective of the study was to compare ecotoxicological data obtained from laboratory experiments on the side-effects of three phenylamide fungicides, pure metalaxyl (racemic mixture of R- and S-enantiomers), formulated metalaxyl and mefenoxam (only active R-enantiomer) on the chemical and biochemical parameters of two soils of different type and origin. The purpose of the comparison was to determine to what extent mefenoxam, developed as alternative to metalaxyl, can affect the activity of soil micro-organisms and their processes, and to elucidate the differences between the effects of pure and formulated metalaxyl. The dynamics of the quantitative changes in biochemical parameters induced by the addition of these fungicides at their recommended field rate were determined in a sandy clay soil from Cameroon and a sandy loam soil from Germany, during a 120-day incubation experiment. The type of soil significantly influenced the effect of these fungicides on the soil parameters studied. Incorporation of these fungicides generally stimulated the activity of phosphatases and ß-glucosidase, mineralization and the availability of N and most plant nutrients in soils. The activity of dehydrogenase and the availability of NO₃^- were generally adversely affected. Among the fungicides tested, the stimulation was more pronounced with mefenoxam followed by formulated metalaxyl.     

Bacteriological studies on the mineralization of organic nitrogen in paddy soils

In this report we studied the effects of mechanical grinding of paddy soils on nitrogen mineralization and bacterial number when soils were incubated under a submerged condition after grinding.

Nitrogen mineralization was increased by grinding soil samples as compared with those without grinding. The value of (Nd-Nu)/Nu, where Nd is the amount of ammonia-nitrogen formed by incubation of disrupted samples and Nu those of the undisrupted soils, was in good correlation with clay/humus ratio.

Although significant difference was not observed between the number of aerobic bacteria with undisrupted and disrupted soil samples, higher anaerobic bacterial numbers were found with disrupted than with undisrupted ones.

A significant correlation was also obtained between the amounts of nitrogen mineralization increased by the grinding of soil and the numbers of anaerobic bacteria.     

不同质地土壤上烤烟氮素积累、分配及利用率的研究

【目的】土壤质地能概括反映土壤内在的肥力特征,对土壤养分供应具有调控作用,是影响农田中土壤氮素供应和氮肥利用的重要因素。本试验通过在皖南烟区3种质地(壤土、黏壤、砂壤)土壤上施用等量氮肥来研究其对烤烟不同生育期的氮素吸收、积累及利用特征的影响,旨在为烟田土壤改良及烤烟合理施肥提供理论依据。【方法】在皖南烟区现代农业科技园的典型壤土、黏壤和砂壤土上分别建立田间试验,采用15N田间微区试验和室内分析相结合的研究方法,在烤烟的团棵期(移栽后38 d)、现蕾期(移栽后53 d)、平顶期(移栽后64d)和成熟期(移栽后103 d),采集长势一致的烟株样品,测定烟株各部位的生物量,并采用凯氏定氮法检测其全氮含量,采用ZHTO2型同位素质谱仪测定其15N丰度。【结果】皖南烟区壤土和黏壤土上烤烟总氮和肥料氮积累均随生育期呈单峰变化,在烤烟平顶期达最大,总氮积累量分别为4.25 g/plant和3.96 g/plant,肥料氮积累量分别为2.34 g/plant和2.54 g/plant,而砂壤土上烤烟到成熟期其总氮和肥料氮的积累量达到最大,分别是5.64 g/plant和2.73 g/plant,均显著高于同时期的壤土和黏壤;壤土、黏壤和砂壤土上烤烟均以叶部肥料氮占总氮比例及氮素分配率较高,茎部次之,根部最低;不同质地土壤上烤烟氮肥利用率与肥料氮的积累动态具有一致的变化趋势,其中壤土和黏壤在平顶期最大,分别为34.5%和40.7%,之后壤土利用率缓慢下降,黏壤下降幅度较大,而砂壤土上烤烟氮肥利用率在生育期内呈上升趋势,至成熟期最大,为43.7%。【结论】不同质地土壤上烟株对氮素的吸收利用顺序为砂壤壤土黏壤,黏壤土在烤烟生育期内供氮能力较弱,应合理调控土壤氮的矿化及增加肥料氮的供应;砂壤土氮肥利用率较高,应严格控制氮肥的施用量。     

稻田土壤供氮能力的解析研究

以太湖地区三种类型水稻土为对象进行的研究表明:(1)风干土淹水培养后,固定态铵平均增加17ppm,相当于交换性铵增量的28%。似应将培养后固定态铵的增量与交换性铵增量之和计为土壤氮素的矿化量。(2)田间微区试验中,耕层以下土壤所供应的氮量占稻田土壤供氮量的16—49%,平均30%。(3)根据所得结果,讨论了用培养法预测稻田土壤供氮量中存在的问题。     

Soil organic matter fractionation as a tool for predicting nitrogen mineralization in silty arable soils

After decades of searching for a practical method to estimate the N mineralization capacity of soil, there is still no consistent methodology. Indeed it is important to have practical methods to estimate soil nitrogen release for plant uptake and that should be appropriate, less time consuming, and cost effective for farmers. We fractionated soil organic matter (SOM) to assess different fractions of SOM as predictors for net N mineralization measured from repacked (disturbed) and intact (undisturbed) soil cores in 14 weeks of laboratory incubations. A soil set consisting of surface soil from 18 cereal and root‐cropped arable fields was physically fractionated into coarse and fine free particulate OM (coarse fPOM and fine fPOM), intra‐microaggregate particulate OM (iPOM) and silt and clay sized OM. The silt and clay sized OM was further chemically fractionated by oxidation with 6% NaOCl to isolate an oxidation‐resistant OM fraction, followed by extraction of mineral bound OM with 10% HF (HF‐res OM). Stepwise multiple linear regression yielded a significant relationship between the annual N mineralization (kg N/ha) from undisturbed soil and coarse fPOM N (kg N/ha), silt and clay N (kg N/ha) and its C:N ratio (R² = 0.80; P < 0.01). The relative annual N mineralization (% of soil N) from disturbed soils was related to coarse fPOM N, HF‐res OC (% of soil organic carbon) and its C:N ratio (R² = 0.83; P < 0.01). Physical fractions of SOM were thus found to be the most useful predictors for estimating the annual N mineralization rate of undisturbed soils. However, the bioavailability of physical fractions was changed due to the disturbance of soil. For disturbed soils, a presumed stable chemical SOM fraction was found to be a relevant predictor indicating that this fraction still contains bio‐available N. The latter prompted a revision in our reasoning behind selective oxidation and extraction as tools for characterizing soil organic N quality with respect to N availability. Nonetheless, the present study also underscores the potential of a combined physical and chemical fractionation procedure for isolating and quantifying N fractions which preferentially contribute to bulk soil N mineralization. The N content or C:N ratio of such fractions may be used to predict N mineralization in arable soils.