不同有机物料与化肥配施对土壤真菌群落结构和生态功能的影响

为减少土壤土传病害,保障农田土壤健康,指导有机物料合理利用,在有机物料用量和化肥用量一致的基础上,设置单施化肥（CK）、羊粪+化肥（A）、木薯渣+化肥（P）、木本泥炭+化肥（M）、味精废浆料+化肥（I）5个处理,以玉米为供试作物进行了有机物料与化肥配施试验,观察了不同处理下土壤真菌群落结构的变化。结果表明：施用有机物料降低了土壤真菌群落多样性,但提高了真菌群落丰富度,其中味精废浆料配施化肥处理的真菌群落丰富度最高,各处理土壤中优势真菌门类均为子囊菌门、担子菌门和被孢菌门。施用有机物料后,木薯渣、木本泥炭和味精废浆料处理的子囊菌门的相对丰度均增加,担子菌门的相对丰度均降低;而羊粪处理表现出相反趋势,子囊菌门的相对丰度降低,担子菌门的相对丰度增加。冗余分析结果表明,土壤pH是影响真菌群落的主要环境因子,其次为有机质、电导率和速效钾,而碱解氮和有效磷的影响较小。另外,有机物料与化肥配施可以提高腐生营养型和共生营养型真菌的比例,减少病原菌的数量,其中以木本泥炭与化肥配施的效果更显著,这有利于维持土壤生态系统的稳定,为作物生产提供健康的土壤条件。     

不同配施比例下秸秆和木本泥炭对快速提升土壤有机质和作物产量的耦合影响

木本泥炭和秸秆配施有快速提升土壤有机质（SOM）和作物产量的潜力，但其配施比例如何影响作物产量及其微生物机制尚不清楚。本研究通过田间试验，在施用秸秆和激发剂（RJ）基础上，比较分析了木本泥炭和秸秆三种施用比例2:1（RJM1）、3:1（RJM2）、4:1（RJM3）对土壤理化性质、细菌群落组成和水稻产量影响，并与不施用有机物料的对照（CK）进行比较；同时基于网络分析和路径分析，明确不同处理特定细菌菌群与作物产量之间潜在关系。结果表明，RJM1、RJM2、RJM3间的水稻产量差异不明显，但平均比RJ和CK显著增产16.09%和31.46%。五个处理按土壤理化性质分成显著不同的三组（P < 0.01），第一组为RJM2+RJM3，以pH、SOM、可溶性有机碳（DOC）、有效磷（AP）、速效钾（AK）含量显著升高为特征；第二组为RJ+RJM1，以硝态氮（NO3--N）和可溶性有机氮（DON）含量显著升高为特征；第三组为CK。RJM2+RJM3的SOM、DOC、AP比RJM1处理平均高29.69%、22.65%和23.95%，表示RJM2+RJM3能迅速提升土壤有机质含量。RJM2和RJM3的细菌群落组成类似，并主要受制于土壤pH、SOM、DOC的变化，但与RJM1的群落组成显著不同。RJM2+RJM3显著增加了与水稻产量正相关的盖勒氏菌（Gaiellaceae unidentified）、类诺卡氏菌（Nocardioidaceae unidentified）、土壤球菌（Terracoccus）、从毛单胞菌（Comamonadaceae unidentified）、WD2101 unidentified、鞘脂杆菌（Sphingobacteriales unidentified）的丰度，而RJM1显著增加了上述除鞘脂杆菌外的其它5个物种的丰度，表示RJM2+RJM3比RJM1刺激更多的与作物产量有正相关的优势物种。上述结果表明，RJM2+RJM3通过改善土壤pH、SOM、DOC，比RJM1刺激更多的有利于作物增产的优势物种；同时由于RJM1的SOM含量与对照没有显著变化，导致其增产的可持续性要低于RJM2+RJM3处理。综合上述结果和经济效益，推荐RJM2，即木本泥炭和秸秆的施用比例为3:1时具有同时快速提升SOM和作物产量的效果。     

秸秆与木本泥炭短期施用对潮土有机质及微生物群落组成和功能的影响

直接添加富含腐殖物质的木本泥炭可快速提升土壤有机碳含量,但其与常规施用秸秆相比的效应如何尚不清楚。通过设置不添加物料(CK)、施用秸秆(R)、施用木本泥炭(MT)、秸秆还田和木本泥炭联合施用(RMT)四个田间试验处理,经过一季玉米生长后比较不同处理对玉米产量、土壤肥力、细菌群落组成和功能的影响。结果表明,R和RMT处理的地上生物量与CK无显著差异,而在玉米整个生育期的平均呼吸速率则分别较CK高40%和64%;MT处理的地上生物量较CK低10%,但MT和CK的平均呼吸速率无显著差异。另一方面,R处理的土壤有机质(SOM)含量与CK无显著差异,而MT和RMT处理的SOM含量则较CK分别高79%和56%。基于主成分分析和功能预测发现,与CK处理比,R处理分解利用新鲜秸秆的绿弯菌门、芽单胞菌门、节细菌属、指孢囊菌属和Rubellimicrobiu显著增多,而化能异养、需氧化能异养、尿素代谢功能显著降低;MT处理降解大分子有机物的土壤杆菌属、纤维菌属、德沃斯氏菌属、农研丝杆菌属、类诺卡氏菌属和Rubellimicrobium显著增多,需氧化能异养功能显著降低,纤维素代谢功能显著升高;而RMT处理与CK群落组成和功能类似。因此,在潮土区单独施用MT尽管能迅速提升SOM含量,但可能导致短期内作物产量降低,而R和MT联合施用在迅速提升SOM的同时可提高土壤呼吸,维持稳定的微生物群落和功能。     

秸秆与有机无机肥配施对潮土关键微生物及小麦产量的影响

秸秆与化肥和鸡粪配施改变了土壤微生物群落结构及微生物间的相互作用关系,但这种变化与小麦产量间的关系尚不清楚。本研究依托7年长期定位试验,选取5个施肥处理：不施化肥+秸秆离田（N0S0）、不施化肥+秸秆还田（N0S）、常规施化肥+秸秆离田（NS0）、常规施化肥+秸秆还田（NS）和施化肥+秸秆还田+鸡粪替代20%氮肥（NSM）,研究了不同施肥方式对细菌-真菌共现网络中微生物组成的影响,以及关键微生物与小麦产量间的相关关系。结果表明,与N0S0处理相比,NS0、NS和NSM处理的小麦籽粒产量分别提升539.20%、611.56%和676.56%,而N0S处理无显著变化。细菌和真菌群落组成均可分成显著不同的3组,分别为N0S0+N0S、NS0以及NS+NSM,即微生物群落组成在是否施用化肥之间显著不同;相同施用化肥情况下,在是否有施用有机物料之间显著不同。将重要性从高到低排序,有效磷（AP）、电导率（EC）、微生物生物量氮（MBN）、土壤有机碳（SOC）、易氧化有机碳（ROC）和颗粒有机碳（POC）是导致不同处理细菌群落结构变化的主要土壤理化性质,EC、MBN、ROC、POC、AP和SOC是导致不同处理真菌群落结构变化的主要土壤理化性质。细菌-真菌共现网络中,两个关键模块（模块1和模块4）与小麦产量变化显著相关。NS+NSM处理提升了模块4中与小麦产量正相关的类诺卡氏菌属（Nocardioides）、纤维单胞菌属（Cellulomonas）、Pir4_lineage、金孢子菌属（Chrysosporium）、无茎真菌属（Acaulium）和裂壳菌属（Schizothecium）等有益菌的相对丰度,它们可降解纤维素和木质素、促进养分转化和循环或抑制病原菌生长;并显著降低了模块1中与小麦产量负相关的葡萄穗霉属（Stachybotrys）、无色穗孢属（Achroiostachys）和Fusicolla的相对丰度,它们为不利于土壤健康和作物生长的植物病原真菌。因此,化肥配施秸秆及化肥配施秸秆和鸡粪利于关键有益微生物增加及病原真菌减少,关键微生物的功能和相对丰度对小麦产量具有影响。     

不同有机物料还田对华北农田土壤固碳的影响及原因分析

中国农业面临着废弃物数量大、污染严重,农田土壤生产力低的现实问题。该研究以增加农田土壤固碳为目标对砂质农田进行有机物料还田,将秸秆、猪粪、沼渣和生物炭4种物料用尿素调节等氮还田,对农田土壤有机碳、颗粒有机碳、可溶性有机碳和微生物量碳的含量进行测定,并探究不同有机物料还田对土壤有机碳的影响原因。研究结果表明:物料还田3a后,生物炭、猪粪和沼渣处理土壤有机碳(SOC)比秸秆处理分别高262.4%、26.8%和20.7%;2014—2015年生物炭处理的土壤微生物量碳(MBC)较秸秆处理降低2.9%~35.5%,猪粪处理和沼渣处理的土壤可溶性有机碳(DOC)分别提高17.1%~60.1%和7.2%~64.8%;2014—2015年生物炭、猪粪和沼渣处理土壤颗粒有机碳(POC)较秸秆处理提高10.8%~148.2%、9.5%~58.3%和11.3%~57.6%;物料还田后,土壤总有机碳(TOC)和POC呈极显著的回归关系(R2=0.67,P0.001),土壤DOC与MBC有极显著相关性(R2=0.52,P0.001)。与秸秆还田相比,生物炭还田有利于土壤POC的累积进而促进土壤有机碳的提升,猪粪和沼渣则通过提高土壤MBC、DOC和POC的含量,促进土壤有机碳的周转和固定。从农田土壤固碳角度而言,生物炭,猪粪和沼渣还田优于秸秆还田。     

有机物料输入稻田提高土壤微生物碳氮及可溶性有机碳氮

土壤微生物量碳、氮和可溶性有机碳、氮是土壤碳、氮库中最活跃的组分,是反应土壤被干扰程度的重要灵敏性指标,通过设置相同有机碳施用量下不同有机物料处理的田间试验,研究了有机物料添加下土壤微生物量碳（soil microbial biomass carbon,MBC）、氮（soil microbial biomass nitrogen,MBN）和可溶性有机碳（dissolved organic carbon,DOC）、氮（dissolved organic nitrogen,DON）的变化特征及相互关系。结果表明化肥和生物碳、玉米秸秆、鲜牛粪或松针配施下土壤微生物量碳、氮和可溶性有机碳、氮显著大于不施肥处理（no fertilization,CK）和单施化肥处理,分别比不施肥处理和单施化肥平均高23.52%和12.66%（MBC）、42.68%和24.02%（MBN）、14.70%和9.99%（DOC）、22.32%和21.79%（DON）。化肥和有机物料配施处理中,化肥+鲜牛粪处理的微生物量碳、氮和可溶性有机碳、氮最高,比CK高26.20%（MBC）、49.54%（MBN）、19.29%（DOC）和32.81%（DON）,其次是化肥+生物碳或化肥+玉米秸秆处理,而化肥+松针处理最低。土壤可溶性有机碳质量分数（308.87 mg/kg）小于微生物量碳（474.71 mg/kg）,而可溶性有机氮质量分数（53.07 mg/kg）要大于微生物量氮（34.79 mg/kg）。与不施肥处理相比,化肥和有机物料配施显著降低MBC/MBN和DOC/DON,降低率分别为24.57%和7.71%。MBC和DOC、MBN和DON随着土壤有机碳（soil organic carbon,SOC）、全氮（total nitrogen,TN）的增加呈显著线性增加。MBC、MBN、DOC、DON、DOC+MBC和DON+MBN之间呈极显著正相关（P<0.01）。从相关程度看,DOC+MBC和DON+MBN较MBC、DOC、MBN、DON更能反映土壤中活性有机碳和氮库的变化,成为评价土壤肥力及质量的更有效指标。结果可为提高洱海流域农田土壤肥力,增强土壤固氮效果,减少土壤中氮素流失,保护洱海水质安全提供科学依据。     

长期免耕旱作对冬小麦生长季土壤剖面有机碳含量的影响

依托21a长期免耕秸秆还田定位试验，探究长期免耕加秸秆还田的田间管理方式对冬小麦生长季0−60cm土层内土壤有机碳（SOC）和土壤活性有机碳（MBC、POC、DOC）的影响。试验共设长期免耕秸秆还田（NT）与常规耕作（CT）两种耕作模式，分析0−60cm土层内土壤总有机碳（SOC）、土壤微生物量碳（MBC）、土壤颗粒有机碳（POC）、土壤可溶性碳（DOC）含量的变化。结果表明，在0−20cm土层，NT处理SOC含量显著高于CT处理，其中0−5cm和5−10cm土层平均SOC含量分别增加了81.2 %和52.9 %，冬小麦不同生育期内土壤SOC含量变化不显著；在0−30cm土层内，与CT处理相比，NT显著改变了土壤MBC、POC及DOC在播种前、越冬前、拔节期、开花期和成熟期5个生育阶段的分布情况，且显著提高了5个生育阶段内土壤活性有机碳的含量（P＜0.05），其中0−5cm土层内，土壤MBC、POC及DOC含量在各个时期相较于CT处理分别增长60.8%～161.4%、71.8%～141.1%和21.9%～104.4%。0−60cm土层内，两种耕作方式下的SOC、MBC、POC、DOC均随着土壤深度的增大呈下降趋势。说明长期免耕可提高耕作层土壤有机碳含量和小麦生长季活性有机碳的水平，这为旱地土壤有机碳的高效固存提供了理论依据。     

有机物料对原生盐碱地土壤生物学性质的影响

采用连续2年大田试验方法,研究了颗粒型秸秆(KL)、正常秸秆(JG)、牧草(MC)以及羊粪(YF)4种有机物料处理对试验地微生物数量、微生物生物量碳氮、土壤呼吸强度、三种土壤酶活性以及水稻产量的影响,并分析了生物学性质与测产指标的相关性。结果表明:与不施有机物料处理(CK)对比,施用有机物料的JG、MC、YF处理均不同程度提高了微生物数量、微生物生物量碳氮含量、土壤呼吸强度、土壤酶活性以及水稻产量,但差异不明显。同种有机物料不同形态之间差异显著,颗粒秸秆效果优于正常秸秆,颗粒秸秆与CK相比,提高了39.45%的土壤细菌、50.28%放线菌、89.91%真菌数量、63.21%和46.02%的土壤微生物生物量碳氮含量,土壤呼吸强度提高46.22%,过氧化氢酶活性提高18.03%,转化酶活性提高23.22%,纤维素酶活性提高79.32%,增产130.6%。土壤微生物数量(细菌、真菌和放线菌)与千粒重、结实率、每穗总粒数和产量具有相关性,土壤微生物活性(土壤呼吸强度和微生物生物量碳氮)与有效穗数、每穗总粒数、千粒重以及产量具有相关性,土壤酶活性(过氧化氢酶、转化酶和纤维素酶)与穗长和千粒重表现出相关性。结果表明相同条件下,原生盐碱地改良前期,不同种类有机物料对原生盐碱地作用效果相似,但同种有机物料不同形态其作用效果差异显著。     

木本泥炭对红黄壤性水田土壤有机质提升和细菌群落组成的影响

通过工程措施开发新垦耕地是增加耕地面积的重要方法,这些新垦耕地的主要问题为土壤有机质(SOM)低下,而农田SOM培育是一个漫长的过程。本研究以新垦红黄壤性水田为研究对象,通过施用腐熟秸秆及与土壤腐殖质结构类似的木本泥炭,明确其快速提升SOM效应。此外,为了促进秸秆养分的快速转化,本研究进一步比较分析了3种商用激发剂的激发秸秆分解潜力,并采用16s高通量测序技术阐明其微生物机制。试验包含6个处理:对照(CK)、施用腐熟秸秆(S)、施用腐熟秸秆+木本泥炭(SP)、以及在SP基础上添加激发剂Ⅰ、Ⅱ、Ⅲ(SPJ1、SPJ2、SPJ3)。结果表明,SP、SPJ1、SPJ2、SPJ3中的土壤有机质(SOM)、易氧化碳(EOC)、可溶性有机碳(DOC)分别比S或CK处理高12.1%～20.6%、29.9%～48.9%、50.8%～75.5%,微生物生物量碳(MBC)则为它们的10.5倍～16.1倍,导致MBC/MBN增加了5.1倍～12.4倍;土壤有效磷(Ava P)和团聚度在SPJ1、SPJ2、SPJ3间类似,并比SP、S、CK处理显著提高44.7%～63.6%、26.4%～43.6%,表明木本泥炭以及本试验所选择的3种激发剂均能显著改善土壤理化性状。细菌多样性和系统发育多样性指数在激发剂施用土壤中均处于较高水平,并分别与DOC和EOC显著正相关。PcoA与Anosim分析发现3种激发剂施用土壤的细菌群落结构类似并与其他处理差异显著,该差异主要与Ava P、DOC、EOC、MBN有关。上述结果表明,通过在新垦水田土壤上施用腐熟秸秆和木本泥炭,可快速提升SOM含量,而在此基础上添加商用激发剂具有激发养分转化功能的微生物的潜力,从而改善土壤理化性质和提升作物产量,并且本研究选择的3种激发剂均有类似效应。     

土壤活性有机碳不同组分对保护性耕作的响应

为分析保护性耕作措施对旱作农田土壤活性有机碳的影响以及对土壤有机碳的敏感响应指标进行归纳总结,探讨适合西南丘陵区紫色土农田生态系统在保护性耕作下的有机碳分组方法和活性碳有效指标提供科学依据,进而为土壤固碳减排、提高土壤质量奠定理论基础。在重庆北碚西南大学试验农场对平作(traditional tillage,T)、垄作(ridge tillage,R)、平作+秸秆覆盖(traditional tillage+straw mulching,TS)和垄作+秸秆覆盖(ridge tillage+straw mulching,RS)4种处理下、西南紫色土丘陵区"旱三熟"种植模式下的土壤总有机碳(Total soil organic carbon,TOC)、颗粒有机碳(Particulate organic carbon,POC)、水溶性有机碳(Dissolved organic carbon,DOC)、易氧化有机碳(Readily oxidized organic carbon,ROC)、可矿化有机碳(Mineralized organic carbon,MOC)以及微生物量有机碳(Microbial biomass carbon,MBC)进行了测定和分析。结果表明,秸秆覆盖不仅增加了表层土壤的TOC,也有利于20cm以上的耕层TOC的增加,而垄作对TOC的影响很小。秸秆覆盖处理下各土层POC均显著高于传统耕作,而单纯的垄作处理对5cm以下土层的POC没有影响,却显著地降低了0-5cm土层POC含量。DOC含量随土层的加深逐渐降低,且不同处理的差异主要出现在表层0-5cm土壤中,5cm以下土壤的DOC含量不易受到耕作措施的影响。TS、RS与对照相比均显著提高0-5cm土层的ROC含量,R与T之间差异不显著,秸秆覆盖只对土壤表层ROC影响很大。T、R、TS、RS处理全年日均土壤呼吸分别为1.84,1.65,2.22,2.21μmol/(m2·s),年土壤呼吸总量分别为696.31,624.41,840.12,836.33g/m2。与对照相比,垄作对土壤呼吸的影响不大,秸秆覆盖加速了土壤呼吸速率。秸秆覆盖处理显著提高了MBC含量,而垄作处理的影响不大。MBC与土壤呼吸速率呈显著正相关,R2介于0.756~0.919之间,P0.05。通过对土壤总有机碳及各组分之间的相关分析分析结果显示,TOC、POC、DOC和ROC在0-5cm土层表现显著的正相关,其他土层没有明显的规律。TOC、POC、DOC、ROC和MBC对耕作措施的响应变化基本一致,表现为对垄作处理的响应不显著,而受秸秆覆盖的影响很大,其中颗粒有机碳占总有机碳的35.74%~49.66%,二者显著正相关,可以作为反映土壤有机碳变化的敏感指标。     

Dynamic interactions of natural organic matter and organic compounds

Purpose

This article reviews our current understanding about how organic chemicals and water interact dynamically with, and therefore coevolve with, soil and sediment natural organic matter (NOM). NOM can be regarded as a polymer-like phase that responds to the input of organic compounds in ways analogous to synthetic polymers.

Methods

Sorption selectivity of organic compounds is shown to result in part from the three-dimensional microstructure of NOM related to its glassy character. Sorption to NOM conforms to polymer theory by exhibiting isotherm shape and irreversible behaviors characteristic of the glassy organic physical state. The glassy state is a metastable state characterized by the presence of excess free volume (holes).

Results

In polymers and NOM, incoming molecules preferentially occupy holes due to the absence of a cavitation penalty. Incoming molecules can enlarge existing holes and create new holes that do not relax completely when the molecules leave. The physical changes in NOM induced by sorption result in hysteresis in the isotherm that persists indefinitely at ambient temperature.

Conclusions

Sorption selectivity and hysteresis have important implications for the fate and bioavailability of contaminants.     

Effective retention of litter-derived dissolved organic carbon in organic layers

This study aimed to gain insight into the generation and fate of dissolved organic carbon (DOC) in organic layers. In a Free Air CO₂ Enrichment Experiment at the alpine treeline, we estimated the contribution of ¹³C-depleted recent plant C to DOC of mor-type organic layers. In an additional laboratory soil column study with 40 leaching cycles, we traced the fate of ¹³C-labelled litter-DOC (22 and 45 mg l⁻¹) in intact Oa horizons at 2 and 15 °C. Results of the field study showed that DOC in the Oa horizon at 5 cm depth contained only 20 ± 3% of less than six-year-old C, indicating minor contributions of throughfall, root exudates, and fresh litter to leached DOC. In the soil column experiment, there was a sustained DOC leaching from native soil organic matter. Less than 10% of totally added litter-DOC was leached despite a rapid breakthrough of a bromide tracer (50 ± 7% within two days). Biodegradation contributed only partly to the DOC removal with 18-30% of added litter-DOC being mineralized in the Oa horizons at 2 and 15 °C, respectively. This was substantially less than the potential 70%-biodegradability of the litter-DOC itself, which indicates a stabilization of litter-DOC in the Oa horizon. In summary, our results give evidence on an apparent ‘exchange’ of DOC in thick organic layers with litter-DOC being retained and ‘replaced’ by ‘older’ DOC leached from the large pool of indigenous soil organic matter.     

土壤有机质对疏水性有机污染物的非线性吸附及其影响因素

土壤有机质(SOM)是土壤的重要组成部分,它对疏水性有机污染物(HOCs)的吸附作用对污染物在环境中的迁移转化有着至关重要的影响。近年来的一些研究表明,HOCs在SOM上的吸附行为并不严格地符合传统的线性分配模型。本文综述了近年来一些学者提出的SOM对HOCs的非线性吸附作用的机制及其影响因素,认为SOM的组成和结构均对HOCs的吸附有着重要的影响。SOM吸附在土壤矿物表面后,其结构或各组分的比例发生了改变,从而对其本身的吸附作用产生影响。溶液的化学环境(主要是阳离子)会对SOM的结构和吸附作用产生影响,特别是当溶液中存在一些过渡金属(如,铜或银)的离子时,共吸附的金属离子可能会与多环芳烃类分子形成阳离子-π键的作用,从而促进多环芳烃类物质在SOM上的吸附。     

不同类型有机物料的有机磷组成及生物有效性

  【目的】  研究不同有机物料的有机磷组成及其作为磷源施用后的供磷能力,为化肥磷的有机替代奠定理论基础。  【方法】  供试有机物料包括粪肥类 (猪粪、羊粪)、绿肥类 (豌豆、苜蓿和绿豆)、秸秆类 (小麦秸秆、玉米秸秆和油菜秸秆)。分析了8种有机物料的全磷、有机磷含量和C/P值,采用Bowman-Cole方法测定了有机磷中的活性 (LOP)、中活性 (MLOP)、中稳性 (MROP) 和高稳性有机磷 (HROP) 4个组分的含量。用供试的8种有机物料进行了小麦盆栽试验,分析了土壤速效磷含量、小麦吸磷量与不同有机物料的有机磷组成、碳/磷 (C/P) 值之间的关系。  【结果】  粪肥、绿肥和秸秆中的全磷含量分别为5.49～5.52、1.19～2.59、0.57～1.07 g/kg,有机物料中有机磷含量占全磷的比例在31.3%～55.2%,除绿豆秸秆外,有机磷含量小于无机磷。有机磷中LOP、MLOP、MROP和HROP的平均比例分别为8.5%、45.2%、41.5%和4.9%。LOP平均含量以粪肥类 (175.5 mg/kg) > 绿肥类 (67.03 mg/kg) > 秸秆类 (25.8 mg/kg);以猪粪、绿豆秸秆的MLOP含量相对较高;MROP含量羊粪 > 猪粪 > 苜蓿秸秆 > 绿豆秸秆 > 豌豆秸秆 > 玉米秸秆 > 油菜秸秆 > 小麦秸秆;HROP在粪肥中的含量显著高于其他类型物料。施用绿肥和粪肥显著增加了小麦的吸磷量和生物学产量,而施用秸秆则不同程度降低了小麦的吸磷量和生物学产量。小麦吸磷量与土壤速效磷含量呈线性正相关关系,与有机物料C/P值呈极显著负相关关系,与LOP、MLOP、MROP呈极显著正相关关系,与HROP相关性不显著;土壤速效磷与有机物料C/P值呈负相关关系。  【结论】  供试有机物料中的全磷含量以粪肥类 > 绿肥类 > 秸秆类,无机磷含量均大于有机磷含量 (绿豆秸秆除外),有机磷以中活性和中稳性有机磷为主。绿肥类和粪肥类物料中含磷量高、且C/P值较低,作为肥料使用能显著增加土壤速效磷含量、小麦生物学产量和吸磷量,可以有效替代一定比例的磷肥。而秸秆类有机物料含磷量较低,且C/P值较高,不适宜作为化肥磷的有机替代物料。     

Contribution of organic amendments to soil organic matter detected by thermogravimetry

Sustainable soil management requires reliable and accurate monitoring of changes in soil organic matter (SOM). However, despite the development of improved analytical techniques during the last decades, there are still limits in the detection of small changes in soil organic carbon content and SOM composition. This study focused on the detection of such changes under laboratory conditions by adding different organic amendments to soils. The model experiments consisted of artificially mixing soil samples from non‐fertilized plots of three German long‐term agricultural experiments in Bad Lauchstädt (silty loam), Grossbeeren (silty sand), and Müncheberg (loamy sand) with straw, farmyard manure, sheep faeces, and charcoal in quantities from 3 to 180 t ha^?1 each. In these mixtures we determined the organic carbon contents by elemental analysis and by thermal mass losses (TML) determined by thermogravimetry. The results confirmed the higher reliability of elemental analysis compared to TML for organic carbon content determination. The sensitivity of both methods was not sufficient to detect the changes in organic carbon content caused by small quantities of organic amendments (3 t ha^?1 or 0.1–0.4 g C kg^?1 soil). In the case of elemental analysis, the detectability of changes in carbon content increased with quantities of added amendments, but the method could not distinguish different types of organic amendments. On the contrary, the based on analysis of degradation temperatures, the TML allowed this discrimination together with their quantitative analysis. For example, added charcoal was not visible in TML from 320 to 330°C, which is used for carbon content determination. However, increasing quantities of charcoal were reflected in a higher TML around 520°C. Furthermore, differences between measured (with TML_110–550) and predicted mass loss on ignition using both organic carbon (with TML₃₃₀) and clay contents (with TML₁₄₀) were confirmed as a suitable indicator for detection of organic amendments in different types of soils. We conclude that thermogravimetry enables the sensitive detection of organic fertilizers and organic amendments in soils under arable land use.     

Influence of mineral and organic fertilizers on soil organic carbon pools

Abstract

The influence of farmyard manure (FYM) and equivalent mineral NPK application on organic matter content, hot water extractable carbon (HWC), microbial biomass C (C_mic), and grain yields in a long-term field experiment was assessed after 40 years in Hungary. The unfertilized plot, FYM fertilized plots and plots fertilized with equivalent NPK fertilizer contained 0.99%, 1.13% and 1.05% total organic carbon (TOC) respectively. Compared to the unfertilized plot, FYM application resulted in 8.2% higher TOC than equivalent NPK fertilization. The highest TOC was only 1.21%, much lower than expected for a soil containing 21.3% of clay. The quantity of HWC varied depending on the type of fertilization: Compared to control, FYM treatments lead to 29% more HWC than mineral fertilization (FYM: 328 mg kg^?1; NPK: 264 mg kg^?1). The impact of FYM and equivalent NPK fertilizer on C_mic was contrary. FYM and NPK resulted in 304 and 423 mg kg^?1 C_mic, respectively. The difference was 119 mg kg^?1; 42% as compared to the unfertilized plot. Despite the higher HWC content, FYM treatments lead to significantly less (35%) grain yields than equivalent NPK doses; C_mic content showed closer correlation to grain yields.     

Compositional characterization of soil organic matter and hot-water-extractable organic matter in organic horizons using a molecular mixing model

Purpose

Microbial decomposition of soil organic matter (SOM) is generally believed to be heterogeneous, resulting in the preferential loss of labile compounds such as carbohydrates and proteins and the accumulation of recalcitrant compounds such as lipids and lignin. However, these fractions are difficult to measure directly in soils. We examined patterns in the biomolecular composition of SOM and hot-water-extractable organic matter (HWEOM) by using a molecular mixing model (MMM) to estimate the content of carbohydrates, protein, lipids, and lignin.

Materials and methods

Organic-horizon soils from Spodosols at the Hubbard Brook Experimental Forest in NH, USA were analyzed for this study. The MMM uses data from elemental analysis (C, H, and N) and ¹³C nuclear magnetic resonance spectroscopy with cross-polarization and magic-angle spinning to estimate the percentage of total C in the various classes of biomolecules.

Results and discussion

Carbohydrate content decreased from about 50 % of the C in recent litter to approximately 35 % in the bottom of the humus layer. Lipids accounted for about 18 % of C in recent litter and increased to 40 % in the lower humus layers. The HWEOM fraction of SOM was dominated by carbohydrates (40–70 % of C). Carbohydrates and lipids in HWEOM exhibited depth patterns that were the opposite of the SOM. The results from the MMM confirmed the selective decomposition of carbohydrates and the relative accumulation of lipids during humus formation. The depth patterns in HWEOM suggest that the solubility of carbohydrates increases during decomposition, while the solubility of the lipid fraction decreases. The MMM was able to reproduce the spectral properties of SOM and HWEOM very accurately, although there were some discrepancies between the predicted and measured H/C and O/C ratios.

Conclusions

The MMM approach is an accurate and cost-effective alternative to wet-chemical methods. Together, carbohydrates and proteins account for up to 85 % of the C in HWEOM, indicating that the HWEOM fraction represents a labile source of C for microbes. Humification resulted in a decrease in carbohydrate content and an increase in lipids in SOM, consistent with investigations carried out in diverse soil environments.     

Recovery rate of organic c in organic matter fractions of Grantsburg soils

Abstract

Walkley‐Black method is a simple and rapid method for organic carbon analysis. Because of incomplete oxidation of organic carbon (C), the recovery of organic C is low with this method. Assuming the 77% recovery of organic C with Walkley‐Black method, the results are corrected with a correction factor of 1.30. The objective of this study is to determine the soil organic C recovery rate and appropriate correction factor for Walkley‐Black (wet combustion) method for tilled soils in southern Illinois. Soil samples were collected in 1995 and 1996 from a trial established in southern Illinois on a moderately well drained, Grantsburg (fine‐silty, mixed, mesic Oxyaquic Fragiudalf) soil. Organic C contents with the Leco analyzer (dry combustion) were significantly higher as compared to the Walkley‐Black method in different tillage systems (no‐till, chisel plow and moldboard plow), soil organic matter fractions (whole soil and mineral fraction) and soil depths (0–5 and 5–15 cm). The recovery percentage of organic C was lower than the assumed percentage with the Walkley‐Black method. No significant differences in organic C recovery percentage were found due to differences in tillage systems and depths, whereas the recovery percentage was lower in mineral fraction as compared to the whole soil. The lower organic C recovery percentage was due to the more stable organic C compounds in the mineral fraction. On the basis of these findings, correction factors of 1.35 and 1.41 are proposed for whole soil and mineral organic C analysis with Walkley‐Black method, respectively for tilled Grantsburg and other similar soils in southern Illinois.     

不同有机肥料对土壤生物活性有机质组分的动态影响

研究了红砂土中加入稻草秸秆和猪粪后土壤中微生物生物量碳、水溶性有机碳、溶解性酚等活性有机质组分的动态变化。有机肥处理一周后 ,微生物生物量碳、水溶性有机碳、溶解性酚等都达到最高值。随着培养时间的推移 ,不同处理的土壤中微生物生物量碳和水溶性有机碳含量都逐渐下降 ,而溶解性酚含量在整个培养过程中基本保持不变。相关分析表明 ,土壤中微生物生物量碳与水溶性有机碳和溶解性酚的含量都呈极显著正相关 ,而水溶性有机碳和溶解性酚的含量不相关。     

Phytovolatilisation of organic chemicals

Features

Independently of the volatilisation of the contaminants from the nutrient solution, the emission rates were determinated under defined, approximated natural conditions by using a dynamic gas exchange chamber. To detect traces of contaminants in air samples with high relative humidity, a purge & trap technology was used. An estimation of the specific emission rates of different materials was made with a transportation model. The model was used to ascertain what compounds are most likely to be emitted by plants due to their physical characteristics.

Results and Conclusions

In experiments with 2,6-Dimethylphenol and Trichloroethylene, a clear link was observed between contaminant emission and the lighting intensity likely to be due to the stomata aperture. The absolute values of the emission rates were very low and in the range of nmol/h m² foliar surface. The calculation of the emission rates in different scenarios shows lowly higher emission rates for materials with lower n-octanol-water partition coefficients

Recommendations and Outlook

Phytovolatilisation is particularly suitable for eliminating volatile compounds in shallow groundwater contaminations, but the experimental proof of an increased net emission of planted areas with volatile soil contaminants near the surface compared with unplanted areas is still pending. On the basis of the model computations it is rather to be expected that the net emission of volatile lipophilic materials should be reduced into the atmosphere by using plants.