火烧迹地不同恢复方式土壤团聚体微生物量碳特征

为探讨不同恢复方式对大兴安岭重度火烧迹地土壤团聚体形成及其团聚体碳循环的影响,以大兴安岭1987年重度火烧后分别经过人工恢复(兴安落叶松、樟子松)和天然恢复的林分为研究对象,分析不同恢复方式下土壤团聚体有机碳、团聚体微生物量碳和团聚体K2SO4浸提碳的分布特征。结果表明:(1)不同林型间土壤团聚体有机碳含量、团聚体微生物量碳含量和团聚体K2SO4浸提碳含量差异显著(P0.05),其大小关系均是兴安落叶松人工林天然次生林樟子松人工林。(2)在不同植被恢复方式下,土壤有机碳含量和微生物量碳含量呈随团聚体粒径增大而增大的趋势,且大团聚体显著高于微团聚体(P0.05),土壤K2SO4浸提碳主要分布于1~0.5mm粒径及其更大粒径团聚体中。(3)土壤团聚体有机碳和团聚体微生物量碳富聚于土壤表层(0—5cm),其含量均随土层深度的增加而减小。除2 mm和2~1mm粒径外,其余粒径团聚体K2SO4浸提碳含量呈随土层深度增加而减小的趋势。(4)土壤微生物量碳与土壤有机碳和K2SO4浸提碳呈极显著正相关(P0.01),说明土壤微生物量碳与有机碳和K2SO4浸提碳之间有密切联系。     

模拟氮沉降对华北落叶松人工林土壤微生物碳和微生物氮的动态影响

为揭示过量的大气氮沉降对华北落叶松人工林土壤微生物碳、氮和土壤呼吸的影响,通过对照(N0:0 g/(m^2·a))、轻度施氮(N1:8 g/(m^2·a))、重度施氮(N2:15 g/(m^2·a))3个外源施氮水平下5年的野外定点试验和观测,模拟过量氮沉降条件下华北落叶松人工林土壤微生物碳、氮和土壤呼吸的变化,旨在阐明林下土壤微生物和呼吸对过量氮沉降的响应及其对土壤碳氮循环的影响。结果表明:在5-10月生长季中,土壤微生物碳和氮的平均含量分别为1 098.93,97.31 mg/kg,二者都随土层深度的增加呈下降趋势;轻度施氮促进土壤微生物碳和氮的增加,重度施氮抑制土壤微生物碳和氮的增加;土壤微生物碳和微生物氮从生长初期5月起,5-7月呈增加趋势,7月出现峰值,8月降低,9-10月小幅增加,呈现"N"形曲线。土壤微生物碳氮比为4.94~18.54,且随施氮量增加而减小。各氮处理下,华北落叶松人工林土壤呼吸速率5,6月较低,7-8月持续增加,并在8月达到最高,9-10月逐渐降低。相关分析表明,土壤呼吸与土壤全氮、含水量、微生物碳和微生物氮含量呈极显著正相关关系,与土壤有机质呈显著正相关关系。在全球变化背景下,研究结果可为进一步明确过量大气氮沉降对森林生态系统碳氮循环的影响途径和机制研究提供重要参考。     

渭北旱塬区不同坡向土地利用类型对土壤性质的影响

为了研究不同坡向土地利用类型对土壤性质的影响,以渭北旱塬区5种土地利用类型(不同坡向)为研究对象,系统分析该区不同坡向土地利用类型剖面土壤物理、化学和生物性质的差异。结果表明:(1)除土壤pH和土壤颗粒组成外,5种土地利用类型土壤含水量、总孔隙度、有机质、全氮、微生物量碳和氮含量总体随土层加深呈下降趋势,土壤容重则相反。(2)0-30cm土层,阳坡农用地土壤含水量、黏粒含量和pH最高,粉粒和全氮含量最低;人工草地砂粒和全氮含量最高,黏粒含量最低;人工林地土壤总孔隙度、土壤有机质、微生物量碳和氮含量最高,土壤含水量、土壤容重和pH最低;天然草地土壤容重和粉粒含量最高,总孔隙度和砂粒含量最低;退耕地有机质、微生物量碳和氮含量最低。阴坡农用地土壤含水量、粉粒含量和pH最高,黏粒和全氮含量最低;人工草地土壤容重、黏粒和微生物量氮含量最高,土壤总孔隙度、粉粒、砂粒和有机质含量最低;人工林地有机质含量和微生物量碳含量最高;天然草地土壤总孔隙度、砂粒和全氮含量最高,土壤容重和pH最低;退耕地土壤含水量、微生物量碳和氮含量最低。(3)5种土地利用类型中,土壤容重、细黏粒、粗黏粒、细粉粒、粗砂粒、土壤pH和有机质(退耕地除外)表现为阳坡阴坡,土壤含水量(退耕地和农用地除外)、总孔隙度、粗粉粒、细砂粒、土壤质地粗化度、全氮(人工草地除外)、土壤微生物量碳和氮含量则为阴坡阳坡。     

马尾松-麻栎混交林土壤溶解性有机碳、氮空间分布特征

以河南省驻马店西部低山丘陵区马尾松—麻栎混交林为研究对象,分析土壤有机碳(SOC)、溶解性有机碳(DOC)和溶解性有机氮(DON)储量及其对坡向、土层深度(0—10cm和10—20cm)及胸高断面积的响应规律。结果表明:坡向和胸高断面积显著影响SOC和DOC储量(p0.05),且不同坡向土壤中SOC、DOC和DON的影响因素不同。阳坡SOC储量主要限制性因素是速效钾,阴坡是全氮;阳坡与阴坡土壤DOC和DON储量主要受全氮的影响。另外,土层深度亦对SOC、DOC和DON储量有显著影响(p0.05),且随土层加深而降低,呈表层富集的现象。相关性分析表明,SOC、DOC和DON储量与土壤物理性质即土壤湿度、紧实度及土壤中颗粒组成存在显著的相关性。SOC、DOC和DON两两之间呈显著正相关关系,并均与土壤全氮、有效氮(铵态氮、硝态氮和碱解氮)、速效磷和速效钾等含量也存在显著的相关性(p0.01),表明土壤养分含量是影响马尾松—麻栎混交林土壤有机碳储量及溶解性有机碳、氮空间分布的重要因素。     

大兴安岭火烧迹地植被恢复中土壤微生物量及酶活性

为了探讨火烧迹地植被恢复过程中土壤微生物量及酶活性变化特征,采用时空互代法,以大兴安岭重度火烧迹地不同恢复年限落叶松人工林为研究对象,对土壤微生物量碳、氮含量及脲酶、碱性磷酸酶、蔗糖酶和过氧化氢酶活性进行了研究。结果表明:(1)土壤养分含量均随土层深度的增加而降低,并在植被恢复过程中呈波动性变化,恢复24a土壤全氮、全磷、有效磷和有机质含量均最高。(2)土壤微生物量碳和氮含量的变化范围分别为267.17~1 764.34mg/kg和23.45~182.14mg/kg,随土层深度的增加而降低。随恢复年限的增加,土壤微生物量碳、氮含量呈上升趋势。(3)植被恢复过程中土壤脲酶、碱性磷酸酶、蔗糖酶和过氧化氢酶活性随土层深度的增加而降低,其中,恢复24a落叶松人工林4种土壤酶活性均显著高于重度火烧迹地。(4)相关分析表明,土壤微生物量与土壤全磷、有效磷和有机质含量均极显著正相关,土壤酶活性与土壤全氮、全磷、水解氮和有机质含量极显著正相关,土壤生物学指标能较好地反映土壤肥力状况。火烧迹地经过24a的恢复,土壤微生物量及酶活性得到了较好的改善。     

不同施肥方式对灌漠土土壤有机碳、无机碳和微生物量碳的影响

利用武威市白云试验站18a长期定位试验资料,研究了不同施肥条件下,土壤有机碳、无机碳和微生物量碳在0-40 cm土层的变化状况.结果表明,氮肥与有机肥长期配合施用和长期施用农肥可以在0 20 cm土层增加土壤有机碳含量,减少土壤中的无机碳含量,增加土壤微生物量碳含量;单施秸秆可增加土壤有机碳,而对无机碳和微生物量碳影响无明显差异;长期施用氮肥对土壤的有机碳、无机碳和微生物量碳均无明显差异.土壤有机碳与土壤无机碳含量呈显著负相关关系,而与土壤微生物量碳呈显著正相关关系.     

黄土区不同类型土壤微生物量碳、氮和可溶性有机碳、氮的含量及其关系

研究了黄土高原南部地区不同土壤类型及不同利用方式下土壤微生物摄碳、氮和可溶性有机碳、氮的含量。结果表明：不同土地利用方式下，土壤微生物量碳、氮和可溶性有机碳、氮含量均为林地〉农田，其中林地枯枝落叶层〉林地O～20cm土层。农田土壤微生物量碳、氮的含量均为红油土〉黑垆土〉淋溶褐土；农田土壤中可溶性有机碳含量为淋溶褐土〉红油土〉黑垆土，而可溶性有机氮含量则为黑垆土〉红油土〉淋溶褐土。方差分析表明，不同土壤类型土壤微生物量氮含量之间的差异达显著水平，而不同土壤类型间土壤微生物量碳、可溶性有机碳、氯含量之间的差异未达显著水平。土壤微生物量碳、氮占土壤有机碳和全氮的比例明显高于可溶性有机碳、氮占土壤有机碳和全氮的比例。相关分析发现，土壤微生物量碳与可溶性有机碳之间以及土壤微生物量氮与可溶性有机氮之间的相关性达显著或极显著水平，说明土壤微生物量碳、氮和土壤可溶性有机碳、氮之间有密切联系。     

春季解冻过程对2种温带森林土壤微生物量碳氮和可溶性有机碳氮的影响

为了研究春季土壤冻融过程对碳氮周转的影响,以长白山地区2种森林土壤为研究对象,利用原位培养连续取样法,测定和分析了土壤微生物量碳(MC)、氮(MN)和可溶性有机碳(DOC)、氮(DON)在春季解冻期间的含量动态变化。结果表明:土壤解冻过程中,2种林型土壤微生物量碳、氮的时间变化动态不同,且土壤微生物量碳、氮表现出明显的垂直空间异质性,0—10cm土层土壤微生物量氮显著高于10—20cm土层。除个别时期外,0—10cm土层土壤微生物量碳亦显著高于10—20cm土层土壤。解冻过程中,2种林型0—10cm土层土壤DOC含量时间变化动态基本一致,而红松阔叶林10—20cm土层土壤最大DOC释放量早于次生白桦林。2种林型DOC释放过程集中于解冻中后期。解冻期2种林型土壤DON时间变化动态表现一致,最大土壤DON释放量出现在解冻中后期。解冻期2种林型土壤DON存在明显的垂直空间分布特征,0—10cm土层土壤DON含量显著高于10—20cm土层。     

黄土高原不同林型植被对土壤活性有机碳及腐殖质的影响

为了探讨植被恢复与重建措施对土壤有机碳作用机制的影响,选取延河流域森林区5种典型林型植被作为研究对象,研究黄土高原辽东栎(Quercus liaotungensis)、侧柏(Platycladus orientalis)、丁香(Syzygium aromaticum)、三角槭(Acer buergerianum)和人工刺槐林(Robinia pseudoacacia)植被0-10cm和10-20cm土层土壤活性有机碳组分和土壤腐殖质特征。结果表明,不同林型植被土壤微生物量碳(MBC)含量表现为辽东栎、丁香和侧柏人工刺槐林三角槭。5种林型植被下,丁香群落土壤表层微生物量碳/有机碳(MBC/SOC)最高(0.034 5),其余依次为人工刺槐林、侧柏、辽东栎,三角槭最低(0.003 5),相比于其他林型植被,丁香更有利于土壤碳积累和碳素的有效利用。土壤易氧化有机碳(EOC)含量表现为辽东栎、侧柏三角槭丁香人工刺槐林。土壤有机碳活度即EOC/(SOC-EOC)表现为侧柏、辽东栎三角槭、丁香人工刺槐林,表明人工刺槐林土壤有机碳稳定性较强。人工刺槐林土壤腐殖化度和聚合度显著高于其余4种植被,其0-10cm,10-20cm土层的(HA/SOC)分别是其他植被的4.75~5.7倍和2.57~3.6倍。     

模拟氮沉降对杉木人工林土壤可溶性有机碳和微生物量碳的影响

在杉木人工林中开展模拟氮沉降试验,设计N0(对照)、N1(60kg N/hm2.a)、N2(120kg N/hm2.a)和N3(240kg N/hm2.a)4种氮沉降水平。通过连续7年的处理后,研究外加氮源对土壤可溶性有机碳及微生物量碳的影响及与土壤酶活性的关系。相同N沉降处理下,土壤有机碳、可溶性有机碳和微生物量碳均随土层加深而降低。氮沉降对土壤有机碳具有促进作用,中-低氮沉降(N1、N2)增加幅度大,高氮沉降(N3)增加幅度小。低氮(N1)处理促进土壤微生物生物量C增加,而中、高氮(N2、N3)则抑制;各氮沉降处理土壤可溶性有机碳含量从高到低的顺序为:N3、N2>N1>N0。40-60cm土壤微生物量碳与蔗糖酶、纤维素酶呈极显著正相关关系,与淀粉酶、多酚氧化酶、过氧化物酶呈极显著负相关关系;除40-60cm土层的β-葡糖苷酶外,各层土壤可溶性有机碳与土壤蔗糖酶、纤维素酶和β-葡糖苷酶活性呈极显著正相关关系,与淀粉酶、多酚氧化酶和过氧化物酶呈极显著负相关关系。因此,氮沉降增加将会对土壤碳累积与分解过程产生较大的影响。     

Altering soil carbon and nitrogen stocks in intensively tilled two-year rotations

Information is needed on the ability of different crop management factors to maintain or increase soil C and N pools, especially in intensively tilled short crop rotations. Soil samples from field experiments in Maine were used to assess the effect of cover crop, green manure (GM) crop, and intermittent or annual amendment on soil C and N pools. These field experiments, of 6–13 years duration, were all characterized by a 2-year rotation with either sweet corn ( Zea mays L.) or potato ( Solanum tuberosum L.), and primary tillage each year. Total, particulate organic matter (POM), and soil microbial biomass (SMB)-C and -N pools were assessed for each experiment. Total C and N stocks were not affected by red clover ( Trifolium pratense L.) cover crop or legume GM, but were increased by 25–53% via a single application of papermill sludge or an annual manure and/or compost amendment. With the exception of continuous potato production which dramatically reduced the SMB-C and SMB-N concentration, SMB-C and -N were minimally affected by changes in cropping sequence, but were quite sensitive to amendments, even those that were primarily C. POM-C and -N, associated with the coarse mineral fraction (53–2,000 µm), were more responsive to management factors compared to total C and N in soil. The change in soil C fractions was a linear function of increasing C supply, across all experiments and treatments. Within these intensively tilled, 2-year crop rotations, substantial C and N inputs from amendments are needed to significantly alter soil C and N pools, although cropping sequence changes can influence more labile pools responsible for nutrient cycling.     

川西平原土壤微生物生物量碳氮磷含量特征及其影响因素分析

本文通过区域调查采样和统计分析,探讨了川西平原土壤微生物生物量碳（MBC）、土壤微生物生物量氮（MBN）和土壤微生物生物量磷（MBP）含量特征及其对气候、海拔、母质和土地利用等因素的响应,揭示了其关键影响因素,以期为川西平原地区土壤质量管理提供参考。结果表明,不同土壤类型的MBC、MBN和MBP含量表现为冲积土显著高于水稻土、潮土和黄壤（P<0.05）,潮土MBC/MBN显著高于水稻土。气候和海拔的影响为：MBC、MBN和MBP含量随着≥ 0℃积温、≥ 10℃积温、年均温和年均降水量的增加呈指数减少,而随干燥度和海拔增加呈线性增加。不同成土母质中,MBC、MBN和MBP含量均为灰色冲积物显著高于老冲积物。不同土地利用方式下,三者含量为草地显著高于水田和旱地,水田、旱地和林地差异不显著。皮尔森相关分析和冗余分析表明,MBC和MBN均与≥ 0℃积温、年均温呈极显著负相关（P<0.01）,与海拔呈极显著正相关关系,MBP与母质呈现极显著负相关关系。逐步回归分析表明,MBC主要受年均温、干燥度、年均降水量和母质的影响;MBN主要受海拔、干燥度和年均降水量的综合影响;MBP主要受母质、年均温、≥ 10℃积温和年均降水量的调控。因此,川西平原土壤MBC、MBN、MBP能灵敏地反映不同采样点气候的变化,可为该区气候变化下土壤碳、氮、磷的响应预测提供参考。     

免耕和秸秆还田对潮土酶活性及微生物量碳氮的影响

利用中国科学院封丘农业生态实验站玉米-小麦轮作保护性耕作定位试验平台,研究了全翻耕（(T)、免耕（(NT)、全翻耕+秸秆还田（(TS)以及免耕+秸秆还田（(NTS)处理分别对田间0 ~ 10、10 ~ 20和20 ~ 30 cm土层酶活性及土壤微生物量碳、氮的影响。结果表明：①在0 ~ 10和10 ~ 20 cm土层内,土壤碱性磷酸酶、转化酶、脲酶、脱氢酶活性为免耕处理大于全翻耕处理,有秸秆还田处理大于无秸秆还田处理,以NTS处理最高,T处理最低;在20 ~ 30 cm土层中,土壤碱性磷酸酶、转化酶、脱氢酶活性免耕处理大于全翻耕处理,土壤碱性磷酸酶、转化酶、脲酶活性有秸秆还田处理大于无秸秆还田处理。②在0 ~10和10 ~ 20 cm土层内,土壤微生物量碳、氮均为免耕处理大于全翻耕处理,有秸秆还田处理大于无秸秆还田处理;在20 ~ 30 cm土层中,微生物量碳以NTS处理最高,微生物量氮以TS处理最高;③4种处理下的土壤酶活性和微生物量碳、氮均随着土层的加深而减少,且在各土层中差异达显著水平。     

Effects of liming and tillage systems on microbial biomass and glycosidases in soils

This study was undertaken to investigate the long-term influence of lime application and tillage systems (no-till, ridge-till and chisel plow) on soil microbial biomass C (C_mic) and N (N_mic) and the activities of glycosidases (- and -glucosidases, - and -galactosidases and -glucosaminidase) at their optimal pH values in soils at four agroecosystem sites [Southeast Research Center (SERC), Southwest Research Center (SWRC), Northwest Research Center (NWRC), and Northeast Research Center (NERC)] in Iowa, USA. Results showed that, in general, the C_mic and N_mic values were significantly (P <0.001) and positively correlated with soil pH. Each lime application and tillage system significantly (P <0.001) affected activities of the glycosidases. With the exception of -glucosidase activity, there was no lime×tillage interaction effect. Simple correlation coefficients between the enzyme activities and soil pH values ranged from 0.51 (P <0.05) for the activity of -glucosidase at the NWRC site (surface of the no-till) to 0.98 (P <0.001) at the SWRC site. To assess the sensitivity of the enzymes to changes in soil pH, the linear regression lines were expressed in activity/pH values. In general, their order of sensitivity to changes in soil pH was consistent across the study sites as follow: -glucosidase>-glucosaminidase>-galactosidase>-galactosidase>-glucosidase. Lime application did not significantly affect the specific activities (g p -nitrophenol released kg^–1 soil organic C h^–1) of the enzymes. Among the glycosidases studied, -glucosidase and -glucosaminidase were the most sensitive to soil management practices. Therefore, the activities of these enzymes may provide reliable long-term monitoring tools as early indicators of changes in soil properties induced by liming and tillage systems.     

Timing patterns of nitrogen application alter plant production and CO2 efflux in an alpine meadow on the Tibetan Plateau,China

Nitrogen (N) availability is an important factor that determines ecosystem productivity and respiration, especially in N-limited alpine ecosystems. However, the magnitude of this response depends on the timing and amounts of N input. Moreover, we have only a limited understanding of the potential effects of the timing of N fertilization on ecosystem carbon (C) and N processes, and activities of the soil microbes. A nitrogen fertilization experiment was conducted in an alpine meadow on the Tibetan Plateau to determine how plant productivity and ecosystem respiration (RE) respond to the timing and amount of N application. In this study, half of the N was added either in the early spring (ES), before the growing season, or in the late fall (LF), after the growing season. All treatments received the other half of the N in mid-July. Three N levels (10, 20, 40 kg N hm⁻² yr⁻¹) were used for each of two N treatments, with no N addition used as a control. Plant aboveground biomass, ecosystem respiration (RE) and soil respiration (RS) were measured for the 2011 and 2012 growing seasons. The LF treatment enhanced ecosystem CO₂ efflux compared with the ES treatment at high N addition levels, resulting from an increase of soil dissolved organic C (DOC) and soil microbial activity. The ES treatment resulted in increased plant aboveground biomass when compared with LF during both growing seasons, although this increase accounted for little variation in ecosystem and soil respiration. Overall, the ES treatment is likely to increase the ecosystem C pool, while the LF treatment could accelerate ecosystem C cycling, especially for the high N treatment. Our results suggest that supplying N during the early stage of the growing season benefits both forage production and soil C sequestration in this alpine ecosystem.     

保护性耕作对麦-豆轮作土壤有机碳全氮及微生物量碳氮的影响

通过设置在甘肃省定西市李家堡镇的保护性耕作措施长期定位试验,共设4个处理（T：传统耕作;NT：免耕无覆盖;TS：传统耕作＋秸秆还田;NTS：免耕＋秸秆覆盖）,采用春小麦豌豆双序列轮作（即小麦→豌豆→小麦和豌豆→小麦→豌豆,本文中所指春小麦地、豌豆地分别指2008年种植春小麦、豌豆的轮作次序）,于2008年3月中旬对春小麦、豌豆双序列轮作下的土壤有机碳、全氮、土壤微生物量碳及土壤微生物量氮含量进行了采样测定。结果表明,经过7a的轮作后,两种轮作次序下,0-30cm土层中土壤有机碳、全氮、土壤微生物量碳、土壤微生物量氮含量均有在免耕＋秸秆覆盖、传统耕作＋秸秆还田处理较免耕不覆盖、传统耕作处理高的趋势,且其含量均随着土壤深度的增加而降低。其中,土壤微生物量碳含量在两种轮作次序下的排序均为：免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉免耕不覆盖（NT）〉传统耕作（T）;而土壤微生物量氮含量在春小麦地和豌豆地的排序则分别表现为：免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉传统耕作（T）〉免耕不覆盖（NT）和免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉免耕不覆盖（NT）〉传统耕作（T）。同时,微生物量碳、微生物量氮与有机碳和全氮均呈显著正相关,说明提高土壤有机质、全氮含量的保护性耕作模式有利于土壤微生物量碳与氮的积累。     

退化红壤马尾松恢复林地土壤微生物生物量变化及其控制因素研究

退化土壤植被恢复后土壤质量在凋落物参与下提高,但恢复土壤理化性质与土壤微生物生物量间的相互作用尚不清楚。本研究目标是调查退化红壤马尾松恢复林地凋落物清除对土壤理化性质和微生物生物量的影响,分析影响土壤微生物生物量的控制因素。研究结果表明,与侵蚀裸地相比,无论凋落物清除与否,马尾松恢复林地的土壤孔隙度、水稳性团聚体比例、土壤有机碳、全氮、土壤微生物生物量均有较大提高;其提高幅度受土层深度和坡位影响,主要表现为表层土壤大于亚表层土壤,坡顶和坡底土壤大于坡中土壤。与凋落物保留林地相比,凋落物清除林地土壤各项指标提高幅度降低。通径分析的结果表明,影响微生物生物量最重要的因素是土壤有机碳含量,其次为土壤孔隙度;凋落物则是通过孔隙度和有机碳来间接影响土壤微生物生物量。本研究说明土壤物理结构恢复对土壤生物学性质的恢复有重要意义。     

<Emphasis Type="Italic">Trichoderma</Emphasis> inoculation and trash management effects on soil microbial biomass,soil respiration,nutrient uptake and yield of ratoon sugarcane under subtropical conditions

A field experiment was conducted during 2003–2005 and 2004–2006 at the Indian Institute of Sugarcane Research, Lucknow, India to study the effect of Trichoderma viride inoculation in ratoon sugarcane with three trash management practices, i.e. trash mulching, trash burning and trash removal. Trichoderma inoculation with trash mulch increased soil organic carbon and phosphorus (P) content by 5.08 Mg ha⁻¹ and 11.7 kg ha⁻¹ over their initial contents of 15.75 Mg ha⁻¹ and 12.5 kg ha⁻¹, respectively. Soil compaction evaluated as bulk density in 0- to 15-cm soil layer, increased from 1.48 Mg m⁻³ at ratoon initiation (in April) to 1.53 Mg m⁻³ at harvest (in December) due to trash burning and from 1.42 Mg m⁻³ at ratoon initiation (in April) to 1.48 Mg m⁻³ at harvest (in December) due to trash mulching. The soil basal respiration was the highest during tillering phase and then decreased gradually, thereafter with the advancement of crop growth. On an average, at all the stages of crop growth, Trichoderma inoculation increased the soil basal respiration over no inoculation. Soil microbial biomass increased in all plots except in the plots of trash burning/removal without Trichoderma inoculation. The maximum increase (40 mg C kg⁻¹ soil) in soil microbial biomass C, however, was observed in the plots of trash mulch with Trichoderma inoculation treatment which also recorded the highest uptake of nutrient and cane yield. On an average, Trichoderma inoculation with trash mulch increased N, P and K uptake by 15.9, 4.68 and 23.6 kg ha⁻¹, respectively, over uninoculated condition. The cane yield was increased by 12.8 Mg ha⁻¹ with trash mulch + Trichoderma over trash removal without Trichoderma. Upon degradation, trash mulch served as a source of energy for enhanced multiplication of soil bacteria and fungi and provided suitable niche for plant–microbe interaction.     

深松一体化播种对夏玉米农田土壤水热特征及微生物动态的影响

为明确深松一体化播种下海河低平原区夏玉米农田土壤水热特性和微生物动态变化,于2012—2013年在河北省农林科学院旱作农业研究所深州试验站,以玉米品种‘郑单958’为试验材料,设置夏玉米深松一体化播种和免耕播种两个处理,从玉米出苗开始,根据生育进程定期测定农田土壤水热特性和微生物状况。结果表明,深松一体化播种处理可提高土壤温度,并扩大温度日较差,玉米全生育期深松一体化播种处理比免耕播种处理土壤温度平均提高1.5%。免耕播种处理有利于表层土壤水分储蓄,而深松一体化播种处理有利于深层土壤水分储蓄。其中,在0~20 cm土层,免耕播种处理比深松一体化播种处理土壤含水量高17.5%;在40~100 cm土层,深松一体化播种处理比免耕播种处理含水量则提高9.2%。在0~40 cm土层中,深松一体化播种处理土壤中真菌数量、细菌数量、土壤微生物量碳和土壤有机碳含量2年平均分别增加26.8%、17.5%、23.5%和57.8%,均显著高于免耕播种处理;放线菌减少18.62%,显著低于免耕播种处理。整体来看,深松一体化播种可促进玉米农田真菌数量、细菌数量、土壤微生物量碳和土壤有机碳含量的增加,扩大土壤温度日较差,提高了土壤对水分的储蓄能力。这对改善海河低平原区夏玉米农田生产力,促进农田可持续利用,提高作物产量具有积极意义。     

Soil organic matter stratification ratio as an indicator of soil quality

Soil quality is a concept based on the premise that management can deteriorate, stabilize, or improve soil ecosystem functions. It is hypothesized that the degree of stratification of soil organic C and N pools with soil depth, expressed as a ratio, could indicate soil quality or soil ecosystem functioning, because surface organic matter is essential to erosion control, water infiltration, and conservation of nutrients. Stratification ratios allow a wide diversity of soils to be compared on the same assessment scale because of an internal normalization procedure that accounts for inherent soil differences. Stratification ratios of soil organic C were 1.1, 1.2 and 1.9 under conventional tillage (CT) and 3.4, 2.0 and 2.1 under no tillage (NT) in Georgia, Texas, and Alberta/British Columbia, respectively. The difference in stratification ratio between conventional and NT within an environment was inversely proportional to the standing stock of soil organic C to a depth of 15–20 cm across environments. Greater stratification of soil C and N pools with the adoption of conservation tillage under inherently low soil organic matter conditions (i.e., warmer climatic regime or coarse-textured soil) suggests that standing stock of soil organic matter alone is a poor indication of soil quality. Stratification of biologically active soil C and N pools (i.e., soil microbial biomass and potential activity) were equally or more sensitive to tillage, cropping intensity, and soil textural variables than stratification of total C and N. High stratification ratios of soil C and N pools could be good indicators of dynamic soil quality, independent of soil type and climatic regime, because ratios >2 would be uncommon under degraded conditions.