秸秆还田对宁南旱区土壤有机碳含量及土壤碳矿化的影响

为了探明秸秆还田对宁南旱区土壤有机碳及土壤碳矿化的影响,为该区作物生产及土壤培肥制度的建立提供参考,通过4a（2007—2010年）秸秆还田定位试验,设置不同秸秆还田量处理,谷子秸秆按3000kg·hm-（2低L）、6000kg·hm-（2中M）、9000kg·hm-（2高H）粉碎还田,玉米秸秆按4500kg·hm-（2低L）、9000kg·hm-（2中M）、13500kg·hm-（2高H）粉碎还田,对照为秸秆不还田,对不同处理条件下土壤有机碳、土壤碳矿化速率、累积矿化量及其与不同形态碳素之间的相关性进行了分析。结果表明,土壤总有机碳、活性有机碳含量均随土层的加深而减少;各处理0～60cm土层土壤有机碳和活性有机碳含量分别比CK显著提高了24.2%、20.8%、9.5%和50.3%、46.6%、34.8%（P〈0.05）;秸秆还田不仅增加了土壤活性有机碳含量,同时也显著提高了0～20cm土层活性有机碳占总有机碳含量的比重,提高幅度达21.1%～23.1%（P〈0.05）;土壤碳矿化速率和累积矿化量在0～60cm各土层内随着秸秆还田量的增加大小顺序均为高量秸秆还田〉中量秸秆还田〉低量秸秆还田〉秸秆不还田,各秸秆还田处理较CK差异显著（P〈0.05）。相关性分析表明,土壤碳累积矿化量与不同形态碳素之间均存在极显著相关性。因此,在宁南半干旱区采用秸秆还田对提高土壤有机碳含量和碳矿化具有明显作用。     

秸秆还田方式对关中盆地土壤微生物量碳氮和冬小麦产量的影响

为了探究秸秆还田方式对土壤碳氮过程、水热过程和作物产量的影响,对比分析了关中平原无秸秆还田(T0)、秸秆覆盖还田(T1)、秸秆翻压还田(T2)和氨化秸秆翻压还田(T3)4种还田方式对冬小麦生育期土壤微生物量碳(MBC)、微生物量氮(MBN)、有机碳(SOC)、全氮(TN)、温度、水分利用效率(WUE)和产量的影响。结果表明:MBC和MBN在整个生育期大致呈现先增加再降低的趋势,在拔节期达到最大值,不同秸秆还田处理在生育期均能有效增加土壤MBC和MBN含量;不同秸秆还田方式均能增加耕作层SOC和TN含量,且对表层(0—10cm)的影响最为明显,大于下表层(10—20cm);T1、T2和T3在前期可提升土壤温度,T2日均温最大,越冬期后降低日平均地温;T3、T1和T2分别增加地上部生物量19.41%,5.63%和11.19%,增加籽粒产量23.48%,20.17%和13.17%,其中T3增产效果达到显著水平,明显优于其他秸秆还田方式;同对照相比,T3、T2和T1可显著提高WUE 28.73%,15.36%和18.83%。T3提高冬小麦籽粒产量和地上部生物量的效果优于其他秸秆还田方式,建议氨化秸秆翻压还田最为优化,对于关中地区旱作农业秸秆还田技术的完善和实践具有一定的指导作用。     

等碳投入的有机肥和生物炭对红壤微生物多样性和土壤呼吸的影响

施用有机肥是快速培育瘠薄土壤的一个重要措施。针对中亚热带第四纪红黏土发育的红壤旱地,建立了玉米和花生单作系统等碳量投入有机肥和生物炭的田间试验,利用聚合酶链式反应—变性梯度凝胶电泳(polymerase chain reaction-denaturing gradient gel electrophoresis,PCR-DGGE)方法研究了土壤细菌和真菌群落组成和多样性的变化,分析了土壤呼吸速率(CO2通量)的变化及其与微生物多样性的关系。两年的试验表明,不同施肥方式导致微生物群落结构显著分异,施用有机肥和生物炭显著增加了细菌多样性,但施肥第二年真菌多样性有下降趋势。秸秆和猪粪配施显著增加了土壤呼吸速率,土壤呼吸速率与细菌和真菌多样性呈显著正相关,细菌多样性对土壤呼吸的影响(相对贡献率为71%)显著高于真菌(29%)。土壤磷素(全磷和速效磷)含量的变化是驱动红壤微生物多样性变化的主导因素,其对细菌和真菌多样性的相对贡献率分别为44.8%和47.4%。因此,合理配施秸秆和猪粪可以快速提高瘠薄红壤的生物功能。     

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。     

秸秆还田与水分管理对稻田土壤微生物量碳、氮及溶解性有机碳、氮的影响

采用田间小区试验,于2011年晚稻季在湖南省长沙县金井镇研究水分管理方式(间歇灌溉和长期淹水)和秸秆还田量(无秸秆还田,低量秸秆还田和高量秸秆还田)对稻田土壤微生物量碳、氮和可溶性有机碳、氮含量的影响。结果表明,在长期淹水的条件下,高量秸秆还田较无秸秆还田可提高土壤微生物量碳、氮和土壤可溶性有机碳、氮的含量;间歇灌溉条件下,低量秸秆还田较高量秸秆还田可提高土壤微生物量碳、氮和土壤可溶性有机碳、氮的含量。无秸秆还田条件下,间歇灌溉处理比长期淹水处理土壤微生物量碳、氮和可溶性有机氮含量高,可溶性有机碳含量低;高量秸秆还田下,长期淹水处理比间歇灌溉处理土壤微生物量碳、氮和可溶性有机碳、氮含量高。不同水分管理方式对不同秸秆还田量下稻田土壤微生物量碳、氮和可溶性有机碳、氮含量影响不同。     

免耕和秸秆还田对土壤酶活性和微生物群落的影响

利用在中国科学院封丘农业生态实验站的玉米-小麦轮作保护性耕作定位实验平台,研究了免耕+秸秆还田、免耕、常耕+秸秆还田、常耕4种耕作方式对玉米生长期内土壤酶活性和土壤微生物群落的影响。结果表明:土壤脲酶、碱性磷酸酶、脱氢酶和转化酶活性为免耕处理大于常耕处理,有秸秆还田处理大于无秸秆还田处理,以免耕+秸秆处理最高,常耕处理最低;玉米不同生育时期,脲酶和碱性磷酸酶分别在苗期和吐丝期出现峰值,转化酶和脱氢酶在苗期较低,增加至吐丝期达到峰值,至成熟期又降至低值;微生物各类群数量表现为免耕处理大于常耕处理,有秸秆处理大于无秸秆处理;土壤脲酶、碱性磷酸酶和转化酶与细菌、真菌、放线菌数量呈显著或极显著正相关关系,脱氢酶仅与放线菌数量呈极显著相关关系。     

小麦和玉米秸秆腐解特点及对土壤中碳、氮含量的影响

通过室内模拟培养试验,揭示了不同水分条件下小麦和玉米秸秆在土壤中的腐解特点及对土壤碳、氮含量的影响。结果表明,1)水分条件对有机物质腐解的影响较大,在32 d的培养期间,相对含水量为60%(M60)时,土壤CO2释放速率始终低于含水量80%(M80)的处理。M60条件下释放的CO2-C量占秸秆腐解过程中释放碳总量的40.1%,而M80条件下达到51.5%;M60条件下,添加秸秆土壤中有机碳含量平均提高2.24 g/kg,显著高于M80条件下的1.43 g/kg。2)添加玉米秸秆的土壤,在培养期内CO2释放速率始终高于小麦秸秆处理,CO2-C累积释放量和有机碳净增量分别为408.35 mg/pot和2.12 g/kg;而小麦秸秆处理分别仅为378.94 mg/pot和1.56 g/kg,两种秸秆混合的处理介于二者之间。3)与未添加秸秆相比,土壤中添加小麦或玉米秸秆后,土壤有机碳、微生物量碳、全氮和微生物量氮含量均显著提高,且数量上总体趋势表现为:玉米秸秆两种秸秆混合小麦秸秆。可见,适宜水分条件有利于秸秆腐解过程中秸秆中碳向无机碳方向转化,而不利于向土壤有机碳方向转化;且玉米秸秆比小麦秸秆更易腐解。秸秆在土壤中腐解对补充土壤碳、氮作用很大,可改善土壤微生物生存条件,提高土壤质量。     

添加生物质炭对红壤水稻土有机碳矿化和微生物生物量的影响

通过室内培育试验,研究了添加生物质炭对江西红壤水稻土有机碳矿化和微生物生物量碳、氮含量的影响。结果表明:红壤有机碳矿化速率在培育第2天达最大值后迅速降低,培养7天后下降缓慢并趋于平稳;添加生物质炭降低了土壤有机碳的矿化速率和累积矿化量,培养结束时,不加生物质炭的对照处理中有机碳的累积矿化量分别比添加0.5%和1.0%生物质炭的处理高10.0%和10.8%。此外,生物质炭的加入显著提高了土壤微生物生物量,添加0.5%生物质炭处理的土壤微生物生物量碳、氮含量分别比对照高111.5%～250.6%和11.6%～97.6%,添加1.0%生物质炭处理的土壤微生物生物量碳、氮含量分别比对照高58.9%～243.6%和55.9%～110.4%。相同处理中,干旱的水分条件下(40%田间持水量)微生物生物量要高于湿润的水分条件(70%田间持水量)。同时,添加0.5%和1.0%的生物质炭使土壤代谢熵分别降低2.4%和26.8%,微生物商减少了43.7%和31.7%。     

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。     

保护性耕作与秸秆还田对土壤微生物及其溶磷特性的影响

试验研究保护性耕作与秸秆还田对土壤微生物及其溶P特性结果表明,免耕和秸秆还田均能促进土壤麦角固醇的增加,而少耕却显著提高土壤微生物生物量。耕作方式间土壤有机碳水平无明显差异,但秸秆还田可提高土壤有机碳含量。免耕处理土壤微生物量显著增加,深耕处理土壤微生物量则较低,秸秆还田微生物量显著高于无秸秆对照。浅耕处理溶P细菌数量最高,免耕最少,但少耕和免耕处理溶P微生物的溶P能力大于深耕及浅耕,秸秆还田对溶P微生物群体和高效溶P菌生长均有促进作用。     

Carbon mineralization in saline soils as affected by residue composition and water potential

In saline soils under semi-arid climate, low matric and osmotic potential are the main stressors for microbes. But little is known about the impact of water potential (sum of matric and osmotic potential) and substrate composition on microbial activity and biomass in field collected saline soils. Three sandy loam soils with electrical conductivity of the saturated soil extract (EC_e) 3.8, 11 and 21 dS m^?1 (hereafter referred to EC3.8, EC11 and EC21) were kept at optimal water content for 14 days. After this pre-incubation, the soils were either left at optimal water content or dried to achieve water potentials of ?2.33, ?2.82, ?3.04 and ?4.04 MPa. Then, the soils were amended with 20 g?kg^?1 pea or wheat residue to increase nutrient supply. Carbon dioxide emission was measured over 14 days; microbial biomass C was measured at the end of the experiment. Cumulative respiration decreased with decreasing water potential and was significantly (P?<?0.05) lower in soils at water potential ?4 MPa than in soils at optimal water content. The effect of residue type on the response of cumulative respiration was inconsistent; with residue type having no effect in the saline soils (EC11 and EC21) whereas in the non-saline soil (EC3.8), the decrease in respiration with decreasing water potential was less with wheat than with pea residue. At a given water potential, the absolute and relative (in percentage of optimal water content) cumulative respiration was lower in the saline soils than in the non-saline soil. This can be explained by the lower osmotic potential and the smaller microbial biomass in the saline soils. However, even at a similar osmotic potential, cumulative respiration was higher in the non-saline soil. It can be concluded that high salt concentrations in the soil solution strongly reduce microbial activity even if the water content is relatively high. The stronger relative decrease in microbial activity in the saline soils at a given osmotic potential compared to the non-saline soil suggests that the small biomass in saline soils is less able to tolerate low osmotic potential. Hence, drying of soil will have a stronger negative effect on microbial activity in saline than in non-saline soils.     

Carbon mineralization in soils of different textures as affected by water-soluble organic carbon extracted from composted dairy manure

The water-soluble organic C in composted manure contains a portion of labile C which can stimulate soil microbial activity. The objective of this experiment was to evaluate the effects of water-soluble organic C extracted from composted dairy manure on C mineralization in soil with different textures. Three soils with textures varying from 3 to 54% clay were amended with 0 to 80 mg water-soluble organic C kg^–1 soil extracted from a composted dairy manure and incubated for 16 weeks at 23°C. The total amount of C mineralized was greater than the amount of C added in the three soils. Differences in mineralizable C with and without added water-soluble organic C were approximately 13–16 times, 4.8–8 times, and 7.5–8 times greater than the amount of C added to clay, loam, and sand soils, respectively. The results of this experiment suggest that immediately following composted manure applications, C mineralization rates increase, and that most of the C mineralized comes mainly from the indigenous soil organic C pool.CLBRR contribution No. 94-71     

Urea-nitrogen transformation and compost-nitrogen mineralization in three different soils as affected by the interaction between both nitrogen inputs

Interactive effects of a combined application of urea and compost on the fates of urea-N and net mineralization of compost-N in three soils with different contents of organic-C and inorganic-N were examined through an aerobic 6-week incubation study. Soils were each subjected to four treatments of urea and compost applied at rates of 0 and 0 mg N kg^-1 (control), 115 and 0 mg N kg^-1, 0 and 115 mg N kg^-1, and 70 and 45 mg N kg^-1, respectively. The interactive effects of a combined application of compost and urea on their N transformations varied depending on the contents of indigenous inorganic-N and organic-C in soils. Urea hydrolysis was increased by compost blending only in soils with a relatively low organic-C content. Compost blending increased N immobilization, thus decreasing nitrification of urea-derived N in soils with high organic-C and inorganic-N contents, whereas the reverse was observed in soils with low nutrient contents. Urea blending, by providing inorganic-N, consistently increased net mineralization of compost-N irrespective of soil characteristics, although the increase was much smaller in soil with high indigenous inorganic-N. From the results, it could be concluded that a combined application of chemical fertilizer would improve the compost use efficiency by increasing mineralization of compost-N particularly in soil with a low inorganic-N content. This study also suggests that compost blending would increase immobilization of urea-N in soils with high C and N contents, whereas it would increase nitrification of fertilizer-N in soils with low nutrients contents, thus resulting in increased NO₃ ^- leaching.     

Carbon and nitrogen mineralization as affected by drying and wetting cycles

Drying and rewetting of soil is an important process in soil aggregation, soil organic matter (SOM) decomposition, and nutrient cycling. We investigated the source of the C and N flush that occurs upon rewetting of dry soil, and whether it is from microbial death and/or aggregate destruction. A moderately well drained Kennebec silt loam (Fine-silty, mixed, superactive, mesic Cumulic Hapludoll) was sampled to a 10 cm depth. Soil under constant water content (CWC) was compared with soil subjected to a series of four dry-wet (DW) cycles during the experimental period (96 d) and incubated at 25 °C. Mineralized C and N were measured during the drying and rewetting periods. Aggregate size distributions were studied by separating the soil into four aggregate size classes (>2000, 250-2000, 53-250, and 20-53 μm) by wet sieving. Repeated DW cycles significantly reduced cumulative N mineralization compared with CWC. The reduction in cumulative mineralized C resulting from DW compared with CWC increased as the DW treatments were subjected to additional cycles. The flush of mineralized C significantly decreased with repeated DW cycles. There was no significant effect on aggregate size distributions resulting from to the DW cycles compared with CWC treatment. Therefore, the flush of mineralized C and N seemed to be mostly microbial in origin in as much as aggregate distribution was unaffected by DW cycles.     

不同种类有机肥碳、 氮矿化特性研究

本文采用室内培养法研究了陕西关中地区日光温室栽培生产中9个不同有机肥的碳、氮矿化特性。结果表明:不同有机肥碳、氮的矿化量和矿化率（矿化量占总有机碳或氮的比例）的动态变化存在明显差异,其中碳矿化率在22.24%～87.16%之间,变异系数达90.30 %;氮矿化率在29.07%～84.87%之间,变异系数达67.37 %;不同类型有机肥相比,鸡粪平均的碳、氮矿化累积量及矿化率显著高于猪粪和牛粪;猪粪与牛粪平均的碳、氮矿化累积量及矿化率无显著差异。同一种类有机肥,培养期间其碳、氮矿化累积量及矿化率也存在明显差异。供试有机肥碳、氮的矿化量与有机肥全氮含量均呈线性关系,表明有机肥氮含量是影响矿化量的主导因子。     

施用钾肥和有机肥对小麦产量、品质的影响

利用布置在河北玉田县的一个钾肥定位试验,研究了在施用氮磷化肥的基础上,施用钾肥和有机肥对小麦子粒产量、17种氨基酸、粗蛋白和粗淀粉含量的影响。结果表明,施用钾肥明显提高了小麦子粒产量,同时提高了天门冬氨酸、蛋氨酸、酪氨酸和赖氨酸的含量;施用有机肥明显提高了蛋氨酸、赖氨酸和脯氨酸的含量;钾肥和有机肥配合施用明显提高了产量、天门冬氨酸、蛋氨酸、酪氨酸和赖氨酸的含量,对上述氨基酸的提高幅度均在10%以上。施用钾肥和(或)有机肥提高了小麦子粒的氨基酸总量、粗蛋白含量,但降低了粗淀粉含量。     

Microbial biomass and C mineralization in agricultural soils as affected by atrazine addition

This study examines the effects of atrazine on both microbial biomass C and C mineralization dynamics in two contrasting agricultural soils (organic C, texture, and atrazine application history) located at Galicia (NW Spain). Atrazine was added to soils, a Humic Cambisol (H) and a Gleyic Cambisol (G), at a recommended agronomic dose and C mineralization (CO₂ evolved), and microbial biomass measurements were made in non-treated and atrazine-treated samples at different time intervals during a 12-week aerobic incubation. The cumulative curves of CO₂–C evolved over time fit the simple first-order kinetic model [Ct = Co (1 − e ^−kt )], whose kinetic parameters were quantified. Differences in these parameters were observed between the two soils studied; the G soil, with a higher content in organic matter and microbial biomass C and lower atrazine application history, exhibited higher values of the total C mineralization and the potentially mineralizable labile C pool than those for the H soil. The addition of atrazine modified the kinetic parameters and increased notably the C mineralized; by the end of the incubation the cumulative CO₂–C values were 33–41% higher than those in the corresponding non-added soils. In contrast, a variable effect or even no effect was observed on the soil microbial biomass following atrazine addition. The data clearly showed that atrazine application at normal agricultural rates may have important implications in the C cycling of these two contrasting acid soils.     

Soil nitrogen mineralization as affected by water and temperature interactions

Summary The hypothesis that water and temperature interact to influence the rate of soil N mineralization was studied in laboratory incubation experiments with two contrasting soils. Small sample rings (10 mm tall, 50 mm diameter) were packed to uniform bulk density with 1–2 mm aggregates of Plano silt loam and Wacousta silty clay loam. Samples were brought to five different water potentials (–0.1, –0.33, –0.5, –1.0, –3.0 bars) using pressure-plate techniques, and the undisturbed sample rings were then incubated at 10–35°C for 3, 10 or 14 days. The concentration of soil exchangeable NH₄ ⁺-N and NO₃ ^–-N was measured at the end of each incubation period on replicate samples. The Q₁₀ of N mineralization was approximately 2 for all tested water potentials. Soil N mineralization was linearly related to water content or log water potential, but no water-temperature interaction was evident. The Q₁₀ was constant with water content, and the scaled water content-N mineralization relationship was constant with temperature. We recommend the use of scaling approaches for assessing interactive effects between water and other environmental factors on N turnover in soils.     

蚯蚓对红壤有机质分解的影响

The earthworms Pheretima carnosa, Drawida gisti and Eisenia foetida were studied to compare their contributions to the decomposition of various organic materials surface-applied on red soil in a 165-day greenhouse experiment. The native species Pheretima carnosa and Drawida gisti were equally effective in accelerating the decomposition of maize residue, according to fresh body weight, while commercial species Eisenia foetida had no significant influence on dry mass loss of maize residue. Liming with CaCO3 or CaO showed little effect on maize residue breakdown involved by Pheretima carnosa, but it inhibited this process involved by Drawida gisti. The capability of Pheretima carnosa to the decomposition of five kinds of organic materials was thoroughly examined. The dry mass losses in worm treatments were in the order of soybean residue ＞ maize residue ＞ pig manure ＞ semi-decayed maize ＞ ryegrass. However, the relative contributions of the earthworm to dry mass loss were in the order of pig manure (89.8%) ＞ semi-decayed maize residue (49.1%) ＞ maize residue (29.4%) ＞ soybean residue (20.9%) ＞ ryegrass residue (16.5%). Pheretima carnosa consumed 20～120 mg dry weight of organic material per gram fresh weight of biomass per day.