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1.
施肥对黑土农田土壤全碳、微生物量碳及土壤酶活性的影响   总被引:19,自引:2,他引:19  
通过对吉林省德惠市中层黑土农田6年定位施肥试验研究表明,施有机肥、秸秆还田+有机肥、秸秆还田+化肥和半量有机肥+化肥处理较单施化肥、未施肥和休闲裸地处理提高了土壤全碳、全氮含量,降低了土壤碳氮比。对玉米播前、抽穗期和收获期土壤微生物量碳测定表明,抽穗期土壤微生物量碳最高,处理间差异显著,且不同采样时期的土壤微生物量碳与土壤全碳含量之间呈高度正相关。对土壤酶活性研究表明,施有机肥较单施化肥、未施肥和休闲裸地处理显著地提高了土壤脲酶、转化酶和过氧化氢酶活性;单施化肥处理对土壤转化酶和过氧化氢酶具有一定的抑制作用;而有机肥、秸秆和化肥之间的配合施用处理的土壤酶活性表现不一致。相关分析显示土壤微生物量碳与土壤酶活性呈显著或极显著正相关。该研究结果表明,长期向中层黑土农田增施有机物,不仅提高了土壤全碳和土壤微生物量碳的含量,而且也提高土壤酶活性,有利于提高土壤养分转化效率,可使黑土质量向健康方向发展。  相似文献   

2.
长期轮作施肥对土壤微生物碳氮的影响   总被引:30,自引:0,他引:30  
就设在黄土高原旱作农耕地上的长期定位试验不同处理土壤微生物量碳氮进行研究,主要就长期不同施肥,种植不同作物及轮作等农业措施对土壤微生物量碳氮的影响进行研究,结果显示,施肥与种植物提高了土壤微生物量碳氮含量,长期施用土粪肥显著提高微生物量碳氮含量,施化肥与有机肥并种植苜蓿处理微生物量碳氮是长期休闲地的3.倍,轮作比连作更有利于微生物量碳氮的提高,轮作与有机肥的施用应当是本区提高土壤肥力的主要途径。  相似文献   

3.
【目的】 施肥能直接或间接改变农田生态系统的养分平衡,从而影响土壤的物理、化学和生物学特性。本研究探讨不同种植制度和土壤条件下施肥对农田土壤生物学特性的影响程度,为合理施肥和土壤肥力提升提供科学依据。 【方法】 通过收集近10年 (2008—2018年) 来发表的文献,建立了包含185组微生物量及群落结构等相关内容的数据库。采用整合分析方法(Meta-analysis),定量分析了施肥对土壤微生物量、群落结构以及酶活性的影响。 【结果】 与不施肥相比,施肥显著提高了土壤微生物磷脂脂肪酸 (PLFA) 和微生物量碳、氮含量,提高幅度分别为28.5%、30.9%和41.6%。施用 (单施或配施) 有机物料对土壤微生物总PLFA含量及微生物量碳、氮含量的提高幅度分别为47.3%、50.4%和58.7%,相当于施用化肥的2.8、2.4和3.9倍。与不施肥相比,施肥均能增加各类微生物菌群PLFA含量,对细菌、真菌及放线菌的提高幅度为23.8%~30.4%,对革兰氏阴性菌(G–)和革兰氏阳性菌 (G+) 的提高幅度为37.8%~43.2%,且施用有机物料处理对各类微生物菌群PLFA含量的提高幅度显著高于施化肥处理。施用化肥对土壤微生物总PLFA含量的提高幅度在一年两熟制区为17.9%,在水田和水旱轮作条件下为18.3%~27.6%,而在一年一熟制区及旱地条件下对土壤微生物总PLFA含量无显著影响。在不同pH的土壤中,施用有机物料对微生物总PLFA的提高幅度均显著高于施化肥处理。在pH < 6与pH > 8的土壤上施用化肥对微生物总PLFA含量无明显影响。施肥显著提高了与土壤有机质分解相关的β-葡萄糖苷酶(42.4%)和乙酰氨基葡萄糖苷酶(174.5%)的活性,对与氮循环相关的亮氨酸氨基肽酶活性无显著影响。统计分析还表明,施肥并未改变土壤微生物的真菌细菌比(F∶B)和革兰氏阳性菌革兰氏阴性菌比(G +∶G–)。 【结论】 在不同种植制度、土地利用类型和土壤pH下,施肥显著改变了土壤微生物量和与有机质分解相关的酶活性,但未改变土壤微生物的真菌细菌比(F∶B)和革兰氏阳性菌革兰氏阴性菌比(G+∶G–)。单施或配施有机物料均有利于提高农田土壤微生物总量及各类菌群的生物量,效果显著好于单施化肥。   相似文献   

4.
长期施用生物有机肥对土壤肥力及微生物生物量碳的影响   总被引:41,自引:1,他引:41  
为了研究施用生物有机肥(EM堆肥,即有效微生物制剂 堆肥)对土壤肥力及微生物生物量碳的影响,进行了7年的施用15t/hm2.a有机肥、施用7.5t/hm2.a有机肥(包括EM堆肥、EM鸡粪肥和传统有机肥)、施用化肥和对照处理的田间试验。结果表明:长期施用生物有机肥的土壤肥力明显提高。随着生物有机肥用量的提高,碱性土壤的pH值逐渐降低,土壤有机质、全N、碱解氮、有效磷、速效钾、微生物生物量碳含量增加,与有机肥施用量呈显著正相关。施用化肥可一定程度提高土壤有机质、全N和有效养分含量,但作用不明显。施肥对土壤肥力和微生物量碳的影响趋势是:EM堆肥>传统堆肥>化肥>对照。土壤微生物量碳与土壤有机质、全N、碱解氮、有效磷、速效钾含量呈显著正相关,可以作为施肥过程中土壤质量变化的生物学指标。  相似文献   

5.
为了探讨长期不同施肥潮土有机碳矿化对添加牛粪的响应特征及添加牛粪对长期不同施肥潮土有机碳矿化的激发效应,以始建于1986年的长期定位试验为平台,通过室内恒温培养的方法研究添加等氮量牛粪后长期不同施肥(不施肥,CK;常量有机肥,SMA;常量化肥,SMF;常量有机无机配施,1/2(SMA+SMF))潮土有机碳矿化、土壤有机碳及活性碳库组分(微生物量碳、可溶性有机碳、颗粒有机碳和易氧化有机碳)含量的变化特征。结果表明:无论添加牛粪与否,长期不同施肥潮土有机碳矿化过程均符合一级动力学方程,而牛粪的添加显著增加了长期不施肥、长期单施化肥和长期有机无机配施土壤的有机碳矿化速率常数,增长幅度分别为21.74%、35.00%和45.00%;添加牛粪提高了长期不同施肥潮土有机碳、微生物量碳、颗粒有机碳和易氧化有机碳含量,却显著降低了可溶性有机碳含量;牛粪对长期不施肥、长期施用常量有机肥、常量化肥和常量有机无机配施潮土有机碳矿化的正激发效应分别达到了48.56%、3.60%、48.43%和3.92%,且对长期不施肥及长期施用常量化肥潮土的激发效应显著高于对长期施用常量有机肥及长期有机无机配施土壤;冗余分析显示添加牛粪对长期不同施肥土壤有机碳矿化的激发效应与土壤活性组分碳氮比呈正相关,与土壤养分含量呈负相关。该研究不仅为合理施用有机肥和实现农田生态系统的可持续发展提供理论依据,还有利于实现农业资源再利用及其效益最大化。  相似文献   

6.
长期施肥对植烟土壤微生物的影响   总被引:6,自引:1,他引:5  
【目的】微生物是土壤的重要组成分,与土壤养分转化供应密切相关。本研究利用12年肥料定位试验研究了云南植烟土壤可培养微生物数量、微生物量碳氮、标记性磷脂脂肪酸(PLFAs)、微生物种群特征及有益微生物的变化。【方法】试验设置不施肥(CK)、单施化肥(CF)和化肥配施有机肥(CFM)处理,在烟株旺长期,采集020 cm耕作层土壤,测定了微生物量碳、氮含量,微生物标记磷脂脂肪酸(PLFAs)含量和可培养微生物数量;鉴定自生固氮菌、磷细菌和钾细菌的数量;根据PLFAs计算了微生物种群特征值。【结果】有机无机肥配施处理的土壤中,可培养细菌比不施肥土壤增加了6.14倍、 真菌增加了2.30倍、 放线菌增加了1.56倍,增幅显著高于化肥处理;施肥显著提高土壤微生物量碳、氮量。化肥和有机无机肥配合处理土壤的微生物量碳分别比CK增加了71.8%和246%;不同施肥处理土壤微生物量碳/氮比值显著不同,分别为14.8(CK)、13.3(CF)和11.2(CFM)。微生物标记性PLFAs含量以化肥有机肥配合处理最高,化肥处理次之,CK最低。化肥、化肥配施有机肥处理土壤细菌PLFAs比对照分别增加了25.41%和87.66%,真菌PLFAs分别增加了15.59%和39.24%,化肥处理代表放线菌的PLFAs降低了24.63%,化肥配施有机肥处理增加了83.86%,表明施肥尤其是化肥配施有机肥改善了土壤环境,促进了微生物的生长繁殖,并改变了土壤微生物种群结构;施肥处理土壤中微生物群落多样性指数上升,化肥处理还提高了微生物的优势度指数,说明施肥有益于增加微生物的种群数量, 化肥配施有机肥处理显著提高了无机磷细菌和钾细菌的数量,两者分别比对照增加了1.15倍和1.02倍,化肥处理则相反,自生固氮菌和无机磷细菌数量分别比CK降低了56.69%和41.30%;化肥配施有机肥处理土壤中的自生固氮菌、磷细菌和钾细菌共有20个属,CK土壤有19个属,化肥处理土壤仅16个属。 【结论】CFM促进微生物生长繁殖,增加种群多样性,有益于微生物固氮、溶磷、解钾,对于提高肥料利用率和保持土壤健康有重要意义。在烟叶栽培过程中,提倡化肥与有机肥配合施用很有必要。  相似文献   

7.
为探究闽江口湿地土地利用和恢复对土壤酶活性的影响,采集闽江口芦苇湿地、滩涂地、草地、农田和撂荒地5种不同土地利用方式,分析土壤β—葡萄糖苷酶、N—乙酰—氨基葡萄糖苷酶、L—亮氨酸—氨基肽酶和酸性磷酸酶活性及与环境因子之间的关系。结果表明:土壤pH、铵态氮和硝态氮在农田土壤显著高于其他土地利用方式;而土壤碳(C)、氮(N)、磷(P)全量含量在撂荒地和芦苇湿地显著高于其他土地利用方式。撂荒地、农田和芦苇湿地可溶性碳氮含量显著高于滩涂和草地土壤;土壤微生物量碳氮含量在不同土地利用方式间变化趋势比较一致,撂荒地均显著高于其他土地利用方式,分别为1 272,124 mg/kg。土壤酶活性变化趋势在不同土地利用方式间基本一致,即撂荒地最高,其次是芦苇湿地和农田,草地和滩涂最低。土壤酶活性矢量长度介于1.12~1.34,矢量角度均大于45°,且土壤胞外酶生态化学计量C∶N∶P总体上为1.00∶1.03∶1.33,表现出主要受磷限制的影响。土壤酶活性与可溶性碳氮、总碳氮和微生物量碳氮均呈显著正相关。研究结果表明,芦苇湿地转化为滩涂等利用方式后土壤碳氮等养分显著降低,而撂荒等方式可提高土壤养分含量,促进土壤微生物活性,进而有利于湿地生态系统的恢复和改善。  相似文献   

8.
通过定位培肥试验对不同培肥方式下黑土生态系统中的土壤微生物活性进行了研究。研究结果表明,不同培肥处理均提高了土壤细菌、富营养菌和寡营养菌的数量,且农肥处理优于化肥处理,单施化肥处理土壤的富营养菌数量苗期最高,而农肥处理和农肥化肥等量处理为先升高后降低,至鼓粒期土壤中的富营养菌数量降至最低。施肥处理土壤微生物量的含量高于对照,农肥处理和农肥化肥等量处理的土壤中微生物量碳、氮含量高于单施化肥处理。不同培肥处理均提高了土壤脲酶的活性,施肥处理土壤脲酶的活性的变化范围为79.56~139.90mg/100g土,农肥低量和农肥高量处理土壤过氧化氢酶之间差异不显著,但显著高于对照,农肥处理土壤过氧化氢酶的含量始终是最高的,平均为0.41ml KMnO4/g干土,农肥化肥等量处理、化肥低量处理和化肥高量处理之间差异不显著,土壤过氧化氢酶含量平均为0.37ml KMnO4/g干土。因此,施用农肥是增加土壤微生物活性的有效途径,有利于提高退化土壤的质量。  相似文献   

9.
长期定位施肥对潮土腐植酸含量及其相关因素的影响   总被引:1,自引:0,他引:1  
利用中国科学院封丘农业生态国家实验站潮土农田生态系统养分平衡长期定位试验地,研究不同施肥处理对春秋两季土壤腐植酸含量、微生物生物量碳及转化酶活性的影响。结果发现,与不施肥对照相比,单施NK或单施PK对土壤pH和有机碳含量均没有显著影响;单施有机肥、施NPK化肥、1/2 OM + 1/2 NPK有机无机配施以及施NP等4种处理均显著抑制了土壤pH的升高,提高了土壤有机碳与全氮含量;其中单施有机肥还显著提高了土壤腐殖质中胡敏酸的含量以及微生物生物量碳和转化酶活性,有机肥与化肥配施效果次之。结果表明,长期施用有机肥更有利于提高土壤肥力质量与健康质量。  相似文献   

10.
不同施肥管理对农田土壤木质素积累的影响   总被引:1,自引:0,他引:1  
《土壤通报》2013,(6):1470-1476
施肥是维持和增加农田土壤有机质的重要管理措施,其中,稳定性土壤有机碳库与长期碳截获密切相关。土壤中木质素对微生物具有高度的抗性,根据其水解性单体的变化,可指示土壤木质素动态、稳定性及其氧化程度。因此,研究利用肥料与肥力长期定位实验,采用碱性氧化铜氧化-气相色谱方法,根据土壤中各木质素单体含量和侧链基团的变化,探讨不同施肥处理对农田黑土中木质素积累和稳定性碳库的影响。实验结果表明,和对照处理(不施肥,CK)相比,化肥施用对020 cm的土壤木质素积累并未产生显著影响,但显著增加了2020 cm的土壤木质素积累并未产生显著影响,但显著增加了2040 cm土壤的木质素含量;长期施用有机肥使040 cm土壤的木质素含量;长期施用有机肥使020 cm和2020 cm和2040 cm的土壤中木质素的含量分别提高了197%40 cm的土壤中木质素的含量分别提高了197%301%和306%301%和306%382%,均与施肥量正相关,同时使0382%,均与施肥量正相关,同时使020 cm的木质素单体的酸醛比显著降低。相对于土壤有机碳来说,长期施用有机肥使020 cm的木质素单体的酸醛比显著降低。相对于土壤有机碳来说,长期施用有机肥使020 cm和2020 cm和2040 cm的木质素来源碳的相对含量分别提高了151%40 cm的木质素来源碳的相对含量分别提高了151%187%和267%187%和267%285%,但是化肥施加仅对20285%,但是化肥施加仅对2040 cm土壤有机碳中木质素来源碳含量产生显著影响。土壤木质素的积累特征和氧化程度在不同施肥处理间的差异表明,化肥施用增加了植物来源木质素的输入,也同时加速了木质素在耕层的周转,所以长期施用化肥并未导致木质素的积累;来源于有机肥的活性碳源的输入降低了木质素的微生物降解作用,有利于稳定性碳的积累,增加了土壤有机碳的可持续利用能力。  相似文献   

11.
低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响   总被引:2,自引:2,他引:0  
【目的】以富士(Fuji)、 秦冠(Qinguan)嫁接在平邑甜茶(Malus hupehensis Rehd.)上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水(ZZ)、 低氮正常水(DZ)、 正常氮干旱(ZG)、 低氮干旱(DG)。氮素和水分均设置两个水平,分别为正常氮(6 mmol/L NO-3-N)、 低氮(0.3 mmol/LNO-3-N)、 正常供水(保持盆中砂子相对含水量为饱和含水量的80%~85%)、 干旱处理(保持盆中砂子相对含水量为饱和含水量的60%~65%)。【结果】富士和秦冠的生物量(茎和叶)、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水(ZZ)>低氮正常水(DZ)>正常氮干旱(ZG)>低氮干旱(DG),并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水(ZZ)>低氮正常水(DZ)>正常氮干旱(ZG)>低氮干旱(DG); 氮、 钾元素含量在植株各部位的分布顺序依次是叶>根>茎,磷元素则是根>叶>茎;光合氮素利用效率(PNUE)和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水(DZ)处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱(DG)处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。  相似文献   

12.
Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.  相似文献   

13.
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.  相似文献   

14.
We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.  相似文献   

15.
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,  相似文献   

16.
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,  相似文献   

17.
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.  相似文献   

18.
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.  相似文献   

19.
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,  相似文献   

20.
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.  相似文献   

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