不同的土壤培肥措施对低肥力农田土壤微生物生物量碳的影响

为了研究华北农田生态系统化肥、秸秆还田和有机肥等培肥措施对土壤微生物生物量碳的影响,在山东省桓台县冬小麦套种夏玉米种植模式下的低肥力生产系统中设置了田间试验。田间试验设7个处理,依序为:①全还 化肥(小麦秸杆 玉米秸杆还田 600kgN/(hm2.a)),②全还 化肥 有机肥(小麦秸杆 玉米秸杆还田 有机肥),③麦还 化肥(小麦秸杆还田 600kgN/(hm2.a)),④麦还 化肥 有机肥(小麦秸杆还田 600kgN/(hm2.a) 有机肥),⑤化肥(600kgN/(hm2.a)),⑥麦还双倍 化肥(加倍小麦秸杆还田 600kgN/(hm2.a)),⑦不施肥(对照)。1998年4月至1998年11月田间取样测定了土壤的微生物生物量碳。试验结果显示:在整个试验阶段提高施肥水平微生物生物量碳都明显增加。单施化肥可以增加土壤的微生物生物量碳,有机物配合施用化肥作用更加明显。不同秸秆还田方式(全还、双倍麦还和麦还)对微生物生物量碳影响的季节变化较大。有机肥对提高土壤微生物生物量碳的作用是很明显的。从微生物生物量碳的全年平均值来看,全还 化肥 有机肥处理>麦还 化肥 有机肥处理>全还 化肥处理>双倍麦还 化肥处理>麦还 化肥处理>化肥处理>对照。因此,低肥力的农田生态系统中最好的培肥措施是化肥配施有机物。     

不同土壤培肥措施对华北高产农田土壤微生物生物量碳的影响

为研究华北高产农田生态系统中化肥、有机肥和秸秆还田等培肥措施对土壤微生物生物量碳的影响,在山东省桓台县冬小麦套种夏玉米的种植模式下设置了田间试验。田间试验设10个处理,依序为:①全还(小麦秸秆 玉米秸秆还田),②麦还(小麦秸秆还田),③全还 化肥1(小麦秸秆 玉米秸秆还田 600kgN/(hm2·a)),④麦还 化肥1(小麦秸秆还田 600kgN/(hm2·a)),⑤全还 化肥2(小麦秸秆 玉米秸秆还田 480kgN/*hm2·a)),⑥麦还 化肥2(小麦秸秆还田 480kgN/(hm2·a)),⑦全还 化肥3(小麦秸秆 玉米秸秆还田 720kgN/(hm2·a)),⑧麦还 化肥3(小麦秸秆还田 720kgN/(hm2·a)),⑨全还 化肥1 有机肥(小麦秸秆 玉米秸秆还田 600kgN/(hm2·a) 有机肥)和⑩化肥1(600kgN/(hm2·a))。1998年4月至1998年11月田间取样测定了土壤的微生物生物量碳。试验结果表明:在高投入的高肥力农业生态系统中,单施化肥土壤的微生物生物量碳下降,化肥抑制了土壤微生物的活性,但是由于有机物的投入,这种抑制作用会减弱。化肥和秸秆还田配合施用时,增量和减量化肥对微生物生物量碳的影响不明显,秸秆还田配合施用化肥能够明显减弱化肥对微生物的抑制作用。有机肥对微生物生物量的促进作用是很明显的。不同秸秆还田方式对微生物生物量碳的影响季节变化较大,但从全年平均值来看全还处理对土壤微生物量碳的影响大于麦还处理。试验中不同处理间微生物量碳有下列趋势:化肥1<麦还 化肥1<麦还 化肥2<全还 化肥2<麦还 化肥3<全还 化肥1<全还 化肥3<麦还<全还<全还 化肥1 有机肥。因此,在高投入集约化的高肥力农田生态系统中,提倡秸秆还田和多施有机肥。     

秸秆还田量对培肥农田黑土氮素初级转化速率的影响

秸秆还田是土壤培肥的重要措施之一,但培肥后土壤对氮素循环的调控功能是否具有可持续性以及与后续秸秆还田数量的关系尚不清楚。本研究对黑土旱地农田进行9年培肥处理后,设置了连续3年秸秆还田处理,秸秆还田量分别为年均秸秆产量(7500 kg·hm^-2)的100%、67%、33%和0,探讨不同秸秆还田量对培肥土壤(0～10 cm)氮素转化过程的影响。结果表明: 秸秆还田通过影响氮素初级转化速率,控制培肥土壤NH₄⁺-N和NO₃^--N的产生与消耗过程。当秸秆还田量低于67%时,NH₄⁺-N生成速率显著降低,而其消耗速率显著提高,土壤保留NH₄⁺-N的能力下降,而NO₃^--N生成速率增加,土壤NO₃^--N固持能力下降,增加NO₃^--N的积累及淋溶损失风险。对于东北旱地农田,利用秸秆归还进行黑土培肥,需要不低于67%收获量的秸秆持续还田才能维持土壤对氮素的保持功能。     

不同熟化措施对黑土母质发育的新成土壤有机碳库的影响

基于8年田间定位试验,采用土壤团聚体分组和闭蓄态微团聚体分离技术,将土壤有机质分为总粗颗粒有机质(活性碳库)、总细颗粒有机质(慢性碳库)和总粉黏粒(惰性碳库) 3个组分,探讨不同熟化措施对黑土母质发育而成的新成土壤总有机碳库及不同活性有机碳库的影响,为黑土严重侵蚀地区母质表露后土壤肥力的快速恢复提供依据。试验设置自然恢复(NatF)、苜蓿种植(Alfa)、无肥(F0C0)、化肥(F1C0)、低量有机肥与化肥配施(F1C1)、高量有机肥与化肥配施(F1C2)等6个熟化处理。结果表明:黑土母质经过8年不同熟化处理后,土壤总有机碳和各组分有机碳含量均显著提高;与NatF相比,有机肥与化肥配施(F1C2和F1C1)对土壤总有机碳的提升作用最为明显,增幅分别为60.7%和41.2%;Alfa其次,增幅18. 2%; F0C0或F1C0处理土壤总有机碳与NatF间无显著差异; F1C2和F1C1处理土壤3个组分有机碳含量均显著高于其他熟化处理,与F1C1相比,F1C2处理对各组分有机碳提升作用更为明显;与NatF相比,Alfa处理土壤有机碳的增加主要表现为粉黏粒结合有机碳的增加; F1C0和F0C0处理土壤总细颗粒有机质和总粉黏粒中有机碳与NatF间无显著差异,总粗颗粒有机质中有机碳含量低于Nat F。研究表明,在米豆轮作和传统耕作体系下,农田生态系统高量有机物料投入配施化肥能够加速黑土母质的熟化进程,快速提高土壤中活性碳库和惰性碳库的容量,是严重退化黑土有机质快速提升的有效措施。     

不同熟化措施对黑土母质发育的新成土壤有机碳库的影响

基于8年田间定位试验,采用土壤团聚体分组和闭蓄态微团聚体分离技术,将土壤有机质分为总粗颗粒有机质(活性碳库)、总细颗粒有机质(慢性碳库)和总粉黏粒(惰性碳库) 3个组分,探讨不同熟化措施对黑土母质发育而成的新成土壤总有机碳库及不同活性有机碳库的影响,为黑土严重侵蚀地区母质表露后土壤肥力的快速恢复提供依据。试验设置自然恢复(NatF)、苜蓿种植(Alfa)、无肥(F0C0)、化肥(F1C0)、低量有机肥与化肥配施(F1C1)、高量有机肥与化肥配施(F1C2)等6个熟化处理。结果表明:黑土母质经过8年不同熟化处理后,土壤总有机碳和各组分有机碳含量均显著提高;与NatF相比,有机肥与化肥配施(F1C2和F1C1)对土壤总有机碳的提升作用最为明显,增幅分别为60.7%和41.2%;Alfa其次,增幅18. 2%; F0C0或F1C0处理土壤总有机碳与NatF间无显著差异; F1C2和F1C1处理土壤3个组分有机碳含量均显著高于其他熟化处理,与F1C1相比,F1C2处理对各组分有机碳提升作用更为明显;与NatF相比,Alfa处理土壤有机碳的增加主要表现为粉黏粒结合有机碳的增加; F1C0和F0C...     

有机物料还田对双季稻田土壤有机碳及其活性组分的影响

有机物料还田是提升农田土壤有机碳、培肥土壤的重要措施。为探讨不同有机物料的还田效果,采用室外培养方法,研究了在等碳输入条件下,施用水稻秸秆、紫云英、生物有机肥、猪粪和水稻秸秆生物炭对洞庭湖双季稻区潮土有机碳和活性有机碳组分含量的影响。结果表明: 经过180 d的培养试验,与不施用有机物料相比,施用有机物料提高了土壤活性有机碳含量。生物有机肥、猪粪和水稻秸秆生物炭处理分别使土壤有机碳含量显著提升了26.1%、9.7%和30.7%,水稻秸秆和紫云英对土壤有机碳含量的提升效应在试验期间并不显著。水稻秸秆和紫云英还田更有利于土壤可溶性有机碳和微生物生物量碳的积累,猪粪更有利于土壤可溶性有机碳的积累,生物有机肥更有利于土壤微生物生物量碳和易氧化有机碳的积累,水稻秸秆生物炭则更有利于土壤微生物生物量碳和轻组有机碳的积累。与水稻秸秆还田相比,紫云英、生物有机肥、猪粪和水稻秸秆生物炭还田使土壤碳库管理指数分别提高了31.8%、111.6%、62.2%和50.7%。从土壤固碳和土壤碳库管理指数来看,生物有机肥、猪粪和水稻秸秆生物炭的还田效果优于水稻秸秆和紫云英还田。     

长期施肥下红壤地区土壤熟化肥力评价

以湖南祁阳中国农业科学院红壤实验站的"生土熟化"长期定位试验(1982—2007年)为基础,运用数值化理论综合评价分析了红壤地区3种母质土壤(花岗岩母质土壤、第四纪红壤、紫色砂页岩土壤)在6种熟化措施(不施肥,CK;不施肥+秸秆还田,CKR;施氮磷钾化肥,NPK;施氮磷钾化肥+秸秆还田,NPKR;施有机物稻草,M;施有机物稻草+秸秆还田,MR)下土壤肥力的变化特征.结果表明:综合肥力指数(IFI)与作物相对产量显著相关,能较好地反映土壤肥力状况.3种土壤IFI均表现为NPK,NPKRM,MRCK,CKR,且均以NPKR处理最高,分别达到了0.77(花岗岩母质土壤)、0.71(第四纪红壤)和0.71(紫色砂页岩土壤),秸秆还田比秸秆不还田处理提高了6.72%～18.83%.3种母质土壤IFI均在熟化7年左右出现一个拐点;IFI的年增加速率表现为:紫色砂页岩土壤(0.016a-1)第四纪红壤(0.011a-1)花岗岩母质土壤(0.006a-1).有机无机肥配施和秸秆还田是快速提高南方红壤地区土壤肥力的重要措施.     

黑土团聚体结合碳对不同有机肥施用量的响应

以连续11年化肥配施不同剂量有机肥的黑土为研究对象,采用团聚体分组与闭蓄态微团聚体分离技术,研究土壤团聚体及其内部组分有机碳对不同有机肥施用量的响应,以期从团聚体尺度揭示黑土有机碳的物理稳定性机制。试验设置4个处理:OM0,仅施化肥;OM1,低量有机肥(7.5 Mg hm~(-2) a~(-1))+化肥;OM2,中量有机肥(15 Mg hm~(-2) a~(-1))+化肥;OM3,高量有机肥(22.5 Mg hm~(-2) a~(-1))+化肥,各处理化肥用量相同。结果显示,与单施化肥相比,有机培肥处理土壤有机碳水平均有显著提升,低量、中量和高量有机肥处理分别提高了7.1%、12.4%和15.7%。有机培肥促进了土壤的团聚化作用,随着有机肥施用量的增加,250—2000μm团聚体含量增加,粉粘粒含量降低,土壤团聚体的稳定性增强,但与中量有机肥相比,高量有机肥输入对土壤团聚化的作用并不明显。有机培肥加速了土壤大团聚体的周转,大团聚体周转速率随着有机肥施用量的增加而加快。有机肥输入并未影响粉黏粒结合有机碳浓度,表明在无有机肥投入的传统管理措施下,黑土粉黏粒已接近或达到碳饱和水平。随着有机肥输入的增加,微团聚体有机碳小幅增加,大团聚体有机碳增加趋势明显,而当有机肥用量最大时,微团聚体有机碳无显著变化,仅大团聚体有机碳仍继续增加,表明高量有机肥投入下微团聚体有机碳库已达到饱和,而更多的新增碳流向大团聚体。对大团聚体内部组分解析发现,高量有机肥处理下大团聚体有机碳的增加主要归因于粗颗粒有机质的增加。这些结果表明,黑土团聚体对有机碳的固持存在由小到大的等级饱和机制,随着有机肥输入的增加,粉粘粒最先达到饱和,然后是微团聚体,而更多的新增碳向周转不断加速的大团聚体富集,固持在活性相对较强的有机碳库—粗颗粒有机质之中。     

不同土壤培肥措施对华北高产农田原生动物丰度的影响

为了解华北高产农田生态系统中秸秆还田、有机肥和化肥投入水平等土壤培肥措施对原生动物群落丰度的影响,1999年10月~2000年9月在山东桓台冬小麦套种夏玉米的田间试验中进行了取样分析。田间处理1~处理9,依序为:全还,麦还,全还 化肥1,麦还 化肥1,全还 化肥2,麦还 化肥2,全还 化肥3,麦还 化肥3和全还 化肥1 有机肥处理。应用3级10倍环式稀释培养法对土壤中鞭毛虫、纤毛虫、肉足虫3类群原生动物的丰度进行了测定。结果显示:该研究地块肥力状况良好;土壤鞭毛虫和肉足虫占有绝大比例,分别为总丰度的39.47%和59.22%,纤毛虫仅占1.31%;土壤原生动物丰度在不同培肥处理中表现出相似的季节性动态变化特征;比较不同土壤培肥措施条件下的原生动物丰度水平为:全还>麦还,全还 化肥1 有机肥>麦还 化肥1,麦还 化肥2,麦还 化肥3>全还 化肥1,全还 化肥2,全还 化肥3;化肥对原生动物丰度表现出明显的抑制作用,而有机肥对原生动力丰度表现出明显的促进作用。化肥的施用量水平对土壤原生动物丰度的影响无显著性差异,作物秸秆采取何种还田方式对土壤原生动物丰度的影响也是不显著的,如麦还 化肥培肥地块的原生动物丰度仅略高于全还 化肥。     

长期施用化肥及秸秆还田对砂姜黑土细菌群落的影响

【目的】在施用化肥的基础上进行秸秆还田是提高砂姜黑土肥力的有效措施,以往的研究只注重秸秆还田对土壤结构、肥力等物理化学性状方面的研究,缺少施肥对砂姜黑土微生物群落影响的研究。本研究以安徽蒙城典型的砂姜黑土为研究对象,以期揭示长期施用化肥和秸秆还田对砂姜黑土细菌群落的影响。【方法】采用454高通量测序对砂姜黑土不同农业施肥措施下的细菌群落进行分析研究,并通过生物信息学的分析方法揭示影响砂姜黑土细菌群落的主要因素。【结果】通过对454高通量测序数据的分析,发现砂姜黑土主要的细菌门类为放线菌、变形菌、酸杆菌、绿弯菌和拟杆菌。长期施用化肥显著提高了砂姜黑土肥力和作物产量,但导致了细菌群落结构的显著变化和多样性的显著降低。秸秆还田有利于土壤肥力的进一步提高,但是并没有缓解长期施用化肥对土壤细菌群落产生的不利影响。分析发现土壤pH的变化是导致土壤细菌群落变异的主要因素。【结论】在施用化肥的基础上进行秸秆还田有利于砂姜黑土肥力的提升,然而并没有缓解由施肥导致的土壤酸化对土壤细菌群落组成和多样性产生的不利影响。这暗示秸秆还田可能并未对砂姜黑土微生物生态产生根本性的有益影响,对于秸秆农田的利用方式还需要进一步研究,以达到农业生产效益和生态效益的并重。     

Photoassimilated carbon allocation in a wheat plant-soil system as affected by soil fertility and land-use history

Background and aims

Carbon (C) cycling in terrestrial ecosystems is influenced by the distribution of photo-assimilated C in the plant-soil system. Photo-assimilated C allocation in a wheat cropping system was examined to identify the links between soil fertility, C partitioning and soil C sequestration.

Methods

A pulse labelling experiment was conducted where ¹⁴CO₂ was introduced to wheat plants grown in two groups of soils of varying fertility: arable soils spiked with nutrients, and soils with differing land-use histories. Wheat shoot, root and soil samples were taken 1, 14 and 28 days after pulse labelling to examine the fluxes of ¹⁴C in the plant-root-soil system.

Results

The partitioning of ¹⁴C in wheat plant-root-soil system was found to vary with time, nutrient spiked soil fertility and land-use history. At the end of the experiment using spiked soils, a positive correlation was observed between the allocation of ¹⁴C in the shoots and soil fertility, whereas in the roots, this relationship was negative. The overall allocation of ¹⁴C in the plant-root system differed significantly between the land-use histories; while in the spiked arable soils ¹⁴C allocation in the shoots and roots systematically followed their fertility status.

Conclusions

There was a weak relationship between C allocation and soil fertility in the soils of different land-use history compared to the strong relationship in the spiked arable soils. This suggests that other factors in the soils under different land uses were more important than nutrient status alone in driving photo-assimilated C allocation. This study demonstrated that soil fertility and land-use history have a crucial role in the allocation of photo-assimilated C in the plant-soil system and are important factors by which C sequestration in soil may be impacted.     

Organic Fertilization and Sufficient Nutrient Status in Prehistoric Agriculture? – Indications from Multi-Proxy Analyses of Archaeological Topsoil Relicts

Neolithic and Bronze Age topsoil relicts revealed enhanced extractable phosphorus (P) and plant available inorganic P fractions, thus raising the question whether there was targeted soil amelioration in prehistoric times. This study aimed (i) at assessing the overall nutrient status and the soil organic matter content of these arable topsoil relicts, and (ii) at tracing ancient soil fertilizing practices by respective stable isotope and biomarker analyses. Prehistoric arable topsoils were preserved in archaeological pit fillings, whereas adjacent subsoils served as controls. One Early Weichselian humic zone represented the soil status before the introduction of agriculture. Recent topsoils served as an additional reference. The applied multi-proxy approach comprised total P and micronutrient contents, stable N isotope ratios, amino acid, steroid, and black carbon analyses as well as soil color measurements. Total contents of P and selected micronutrients (I, Cu, Mn, Mo, Se, Zn) of the arable soil relicts were above the limits for which nutrient deficiencies could be assumed. All pit fillings exhibited elevated δ¹⁵N values close to those of recent topsoils (δ¹⁵N>6 to 7‰), giving first hints for prehistoric organic N-input. Ancient legume cultivation as a potential source for N input could not be verified by means of amino acid analysis. In contrast, bile acids as markers for faecal input exhibited larger concentrations in the pit fillings compared with the reference and control soils indicating faeces (i.e. manure) input to Neolithic arable topsoils. Also black carbon contents were elevated, amounting up to 38% of soil organic carbon, therewith explaining the dark soil color in the pit fillings and pointing to inputs of burned biomass. The combination of different geochemical analyses revealed a sufficient nutrient status of prehistoric arable soils, as well as signs of amelioration (inputs of organic material like charcoal and faeces-containing manure).     

植物篱对紫色土区坡耕地水土流失及土壤肥力的影响

植物篱的水土保持效果已得到广泛的认可,并在世界很多地方推广应用,然而,到目前为止,植物篱对坡耕地土壤肥力的影响规律研究却很少。利用长期定位小区试验,研究了植物篱对坡耕地土壤肥力的影响规律,旨在弄清植物篱提高土壤肥力的作用与效果,不断完善植物篱技术。研究发现,坡耕地在建立植物篱后,土壤粘粒在篱前富积,篱下加剧侵蚀,粘粒的富积与侵蚀沿等高线成水平带状分布;土壤有机质、N、P等主要营养元素出现与土壤颗粒相同的分布规律;对K来说,其分布不受植物篱的影响,表现出较为均一分布的特点。从土壤养分的绝对数量来看,P呈高度富积,而有机质和K则是高度耗竭。因此,坡耕地施肥时可以适当减少P的施用量,增加有机物和K的施用量。针对植物篱带对坡耕地肥力影响的特点,即篱前肥力升高,篱下肥力下降,在坡耕地管理上应特别加强篱下土壤带的培肥,以提高坡面整体生产能力。     

Management options for reducing CO2 emissions from agricultural soils

Crop-based agriculture occupies 1.7 billion hectares, globally, with a soil C stock of about 170 Pg. Of the past anthropogenic CO² additions to the atmosphere, about 50 Pg C came from the loss of soil organic matter (SOM) in cultivated soils. Improved management practices, however, can rebuild C stocks in agricultural soils and help mitigate CO² emissions.Increasing soil C stocks requires increasing C inputs and/or reducing soil heterotrophic respiration. Management options that contribute to reduced soil respiration include reduced tillage practices (especially no-till) and increased cropping intensity. Physical disturbance associated with intensive soil tillage increases the turnover of soil aggregates and accelerates the decomposition of aggregate-associated SOM. No-till increases aggregate stability and promotes the formation of recalcitrant SOM fractions within stabilized micro- and macroaggregate structures. Experiments using¹³ C natural abundance show up to a two-fold increase in mean residence time of SOM under no-till vs intensive tillage. Greater cropping intensity, i.e., by reducing the frequency of bare fallow in crop rotations and increasing the use of perennial vegetation, can increase water and nutrient use efficiency by plants, thereby increasing C inputs to soil and reducing organic matter decomposition rates.Management and policies to sequester C in soils need to consider that: soils have a finite capacity to store C, gains in soil C can be reversed if proper management is not maintained, and fossil fuel inputs for different management practices need to be factored into a total agricultural CO² balance.     

不同还田方式对砂质潮土理化性质及微生物的影响

为探索不同物料还田方式对中低产田砂质潮土的改良效果,在黄淮海平原麦玉轮作区典型砂质潮土上进行了连续6季的田间小区试验,设置全量秸秆翻耕还田(TS),秸秆等碳量的生物炭(TB)及半量秸秆半量生物炭配合翻耕还田(TSB),全量秸秆免耕覆盖还田(NTS)和半量秸秆半量生物炭配合免耕覆盖还田(NTSB),共5种还田方式。结果表明,与常规秸秆翻耕还田(TS)相比,生物炭翻耕还田(TB)显著降低土壤容重,增加玉米各个生育期土壤水分和p H值,有机质含量提升了16.4%,但TB处理的土壤大团聚体降低了21.2%和微生物数量降低了16.1%;翻耕秸秆配合生物炭还田(TSB)除了显著降低了大团聚体数量,对其余理化及微生物指标的影响均不显著;免耕模式下的秸秆还田(NTS)和秸秆生物炭配施(NTSB)分别在玉米生长的喇叭口期和收获期显著增加了土壤水分含量、耕层土壤的微生物数量和有效降低砂质潮土分形维数,对容重和有机质含量有一定的改善,其中NTSB有机质含量提升了14.9%和微生物数量增加了53.7%,对砂质潮土改良效果更好。总体来说,短期内用等碳量的生物炭替代秸秆翻耕还田更多的表现为物理的掺混效应,虽能有效提升土壤有机质含量,但不能有效改善砂质潮土的物理结构及生物性质,一半秸秆用生物炭替代还田对该类土壤的理化及微生物指标的改良效果也不显著,而免耕条件下秸秆配合生物碳还田效果最佳,可为砂质潮土的改良提供新的途径和理论依据。     

盐渍化条件下土壤团聚体及其有机碳研究进展

土壤团聚体是土壤结构的基本单元,对改善土壤结构和增加土壤固碳具有重要作用.盐渍化导致的特殊土壤性质,如高盐分离子(主要为Na+)浓度、低有机质含量和较差的微生物条件等因素,对团聚体的形成和稳定产生障碍作用,因此探讨盐渍化土壤团聚体特征更具有重要性和特殊性.滨海湿地和内陆盐渍化沼泽湿地是盐渍化生态系统的重要组成部分.本文...     

不同施肥对退化稻田土壤肥力恢复的影响

为了探明不同施肥修复措施对退化水稻土壤肥力的修复作用,自2005年起采用盆栽试验连续3年对长期缺肥退化水稻土进行了土壤肥力培肥试验研究。结果表明:6种施肥修复措施均可以显著地改善退化水稻土的肥力特征,土壤有机质含量最多提高了14.0%,土壤有效磷显著增加,最高增加量达到39.0mg.kg-1,土壤速效钾均恢复到中等水平(80mg.kg-1)以上,但土壤碱解氮除水稻专用复合肥(ZY)处理基本维持试验前水平外,其他施肥措施均有所下降;不同施肥修复措施均可明显地提高土壤微生物数量、微生物活性以及微生物生物量C、N、P含量,但以有机无机肥配合效果最佳;有机无机肥配合还可以促进稻谷产量和显著提高肥料农学效率;对于长期不施肥导致的退化稻田土壤肥力的修复以在施用水稻专用复合肥的基础上配施有机肥的效果最佳。     

Effects of soil erosion on crop productivity

Soil erosion and the effects of soil erosion on crop productivity have become emotional issues and have attracted the attention of agriculturists, environmentalists, and the public in general. In spite of heavy investments in research and development, the global rates of accelerated erosion are now presumbly higher than ever before. However, the data from available records obtained by diverse methods are uncomparable, unreliable, confusing, and often vary by several orders of magnitude. Reports of erosion‐caused alterations in crop productivity and soil properties are also contradictory and subjective. In addition to the lack of standardized methodology in evaluating soil erosion and its effects on crops, controversial interpretations are attributed to differences in soil profile characteristics, nutrient status, crops grown, and prevailing climatic conditions. Although erosion is generally associated wtih yield reductions, there are examples of where soil erosion has had no effect or has had a positive effect on crop production. Accelerated erosion affects productivity both directly and indirectly. Directly, the erosion‐induced reduction in crop yields is attributed to loss of rooting depth, degradation of soil structure, decrease in plant‐available water reserves, reduction in organic matter, and nutrient imbalance. Depending on soil properties and the degree of degradation, adverse effects of erosion on crop yields can be mostly compensated for by additional inputs of macronu‐trients (N, P, K) and macronutrients plus organic matter, by supplemental applications of some micronu‐trients, and by irrigation. For some soils, e.g., tropical soils, crop yields from severely eroded soils are significantly lower than those from uneroded lands and are often uneconomic in spite of additional inputs. Specific examples of yield alterations are given in relation to the loss of plant nutrients, soil water reserves, and alterations in soil properties. Criteria for soil‐loss tolerance are discussed, and productivity restoration of eroded soils is reviewed in relation to soil organic matter content and nutrient requirments. Research and development priorities are presented.     

Municipal solid waste compost amendment in agricultural soil: changes in soil microbial biomass

Agricultural application of Municipal Solid Waste (MSW), as nutrient source for plants and as soil conditioner, is the most cost-effective option of MSW management because of its advantages over traditional means such as landfilling or incineration. However, agricultural application of MSW can lead to a potential environmental threat due to the presence of pathogens and toxic pollutants. Composting is an attractive alternative of MSW recycling. Application of MSW compost (MSWC) in agricultural soils can directly alter soil physico-chemical properties as well as promote plant growth. The soil microbial biomass, considered as the living part of soil organic matter, is very closely related to the soil organic matter content in many arable agricultural soils. Numerous studies, with different MSWC amendment doses on different soil types and under different water regimes revealed no detrimental effect on soil microbial biomass. In this review, we show the state of art about the effects of MSWC amendment on soil microbial biomass.     

Microbial mechanisms of carbon priming effects revealed during the interaction of crop residue and nutrient inputs in contrasting soils

Agronomic practices such as crop residue return and additional nutrient supply are recommended to increase soil organic carbon (SOC) in arable farmlands. However, changes in the priming effect (PE) on native SOC mineralization in response to integrated inputs of residue and nutrients are not fully known. This knowledge gap along with a lack of understanding of microbial mechanisms hinders the ability to constrain models and to reduce the uncertainty to predict carbon (C) sequestration potential. Using a ¹³C‐labeled wheat residue, this 126‐day incubation study examined the dominant microbial mechanisms that underpin the PE response to inputs of wheat residue and nutrients (nitrogen, phosphorus and sulfur) in two contrasting soils. The residue input caused positive PE through “co‐metabolism,” supported by increased microbial biomass, C and nitrogen (N) extracellular enzyme activities (EEAs), and gene abundance of certain microbial taxa (Eubacteria, β‐Proteobacteria, Acidobacteria, and Fungi). The residue input could have induced nutrient limitation, causing an increase in the PE via “microbial nutrient mining” of native soil organic matter, as suggested by the low C‐to‐nutrient stoichiometry of EEAs. At the high residue, exogenous nutrient supply (cf. no‐nutrient) initially decreased positive PE by alleviating nutrient mining, which was supported by the low gene abundance of Eubacteria and Fungi. However, after an initial decrease in PE at the high residue with nutrients, the PE increased to the same magnitude as without nutrients over time. This suggests the dominance of “microbial stoichiometry decomposition,” supported by higher microbial biomass and EEAs, while Eubacteria and Fungi increased over time, at the high residue with nutrients cf. no‐nutrient in both soils. Our study provides novel evidence that different microbial mechanisms operate simultaneously depending on organic C and nutrient availability in a residue‐amended soil. Our results have consequences for SOC modeling and integrated nutrient management employed to increase SOC in arable farmlands.