Maize straw application as an interlayer improves organic carbon and total nitrogen concentrations in the soil profile: A four-year experiment in a saline soil

Soil salinization is a critical environmental issue restricting agricultural production.Deep return of straw to the soil as an interlayer (at 40 cm depth) has been a popular practice to alleviate salt stress.However,the legacy effects of straw added as an interlayer at different rates on soil organic carbon (SOC) and total nitrogen (TN) in saline soils still remain inconclusive.Therefore,a four-year (2015–2018) field experiment was conducted with four levels (i.e.,0,6,12and 18 Mg ha~(–1)) of straw returned as an interlayer.Compared with no straw interlayer (CK),straw addition increased SOC concentration by 14–32 and 11–57%in the 20–40 and 40–60 cm soil layers,respectively.The increases in soil TN concentration (8–22 and 6–34%in the 20–40 and 40–60 cm soil layers,respectively) were lower than that for SOC concentration,which led to increased soil C:N ratio in the 20–60 cm soil depth.Increases in SOC and TN concentrations in the 20–60 cm soil layer with straw addition led to a decrease in stratification ratios (0–20 cm:20–60 cm),which promoted uniform distributions of SOC and TN in the soil profile.Increases in SOC and TN concentrations were associated with soil salinity and moisture regulation and improved sunflower yield.Generally,compared with other treatments,the application of 12 Mg ha~(–1) straw had higher SOC,TN and C:N ratio,and lower soil stratification ratio in the2015–2017 period.The results highlighted that legacy effects of straw application as an interlayer were maintained for at least four years,and demonstrated that deep soil straw application had a great potential for improving subsoil fertility in salt-affected soils.

Effects of straw and biochar addition on soil nitrogen,carbon,and super rice yield in cold waterlogged paddy soils of North China

The additions of straw and biochar have been suggested to increase soil fertility, carbon sequestration, and crop produc- tivity of agricultural lands. To our knowledge, there is little information on the effects of straw and biochar addition on soil nitrogen form, carbon storage, and super rice yield in cold waterlogged paddy soils. We performed field trials with four treatments including conventional fertilization system （CK）, straw amendment 6 t ha^-1 （S）, biochar amendment 2 t ha^-1 （C1）, and biochar amendment 40 t ha^-1 （C2）. The super japonica rice variety, Shennong 265, was selected as the test Crop. The results showed that the straw and biochar amendments improved total nitrogen and organic carbon content of the soil, reduced N2O emissions, and had little influence on nitrogen retention, nitrogen density, and CO2 emissions. The S and C1 increased NH4^＋-N content, and C2 increased NO3^--N content. Both S and C1 had little influence on soil organic carbon density （SOCD） and C/N ratio. However, C2 greatly increased SOCD and C/N ratio. C1 and C2 significantly improved the soil carbon sequestration （SCS） by 62.9 and 214.0% （P〈0.05）, respectively, while S had no influence on SCS. C1 and C2 maintained the stability of super rice yield, and significantly reduced CH4 emissions, global warming potential （GWP）, and greenhouse gas intensity （GHGI）, whereas S had the opposite and negative effects. In summary, the biochar amendments in cold waterlogged paddy soils of North China increased soil nitrogen and carbon content, improved soil carbon sequestration, and reduced GHG emission without affecting the yield of super rice.

The Effects of Three Mineral Nitrogen Sources and Zinc on Maize and Wheat Straw Decomposition and Soil Organic Carbon

The incorporation of straw in cultivated ifelds can potentially improve soil quality and crop yield. However, the presence of recalcitrant carbon compounds in straw slow its decomposition rate. The objective of this study was to determine the effects of different nitrogen sources, with and without the application of zinc, on straw decomposition and soil quality. Soils were treated with three different nitrogen sources, with and without zinc： urea （CO（NH2）2）, ammonium sulfate （（NH4）2SO4）, and ammonium chloride （NH4Cl）. The combined treatments were as follows：maize （M） and wheat （W） straw incorporated into urea-, ammonium sulfate-, or ammonium chloride-treated soil （U, S, and C, respectively） with and without zinc （Z） （MU, MUZ, WU, WUZ;MS, MSZ, WS, WSZ;MC, MCZ, WC, WCZ, respectively）;straw with zinc only （MZ, WZ）;straw with untreated soil （MS, WS）;and soil-only or control conditions （NT）. The experiment consisted of 17 treatments with four replications. Each pot contained 150 g soil and 1.125 g straw, had a moisture content of 80%of the ifeld capacity, and was incubated for 53 days at 25°C. The rates of CO2-C emission, cumulative CO2-C evolution, total CO2 production in the soils of different treatments were measured to infer decomposition rates. The total organic carbon （TOC）, labile organic carbon （LOC）, and soil microbial biomass in the soils of different treatments were measured to infer soil quality. All results were signiifcantly different （P〈0.05） with the exception of the labile organic carbon （LOC）. The maize and wheat straw showed different patterns in CO2 evolution rates. For both straw types, Zn had a synergic effect with U, but an antagonistic effect with the other N sources as determined by the total CO2 produced. The MUZ treatment showed the highest decomposition rate and cumulative CO2 concentration （1 120.29 mg/pot）, whereas the WACZ treatment had the lowest cumulative CO2 concentration （1 040.57 mg/pot）. The addition of NH4Cl resulted in the highest total organic carbon （TOC） concentration （11.59 mg kg-1）. The incorporation of wheat straw resulted in higher microbial biomass accumulation in soils relative to that of the maize straw application. The results demonstrate that mineral N sources can affect the ability of microorganisms to decompose straw, as well as the soil carbon concentrations.

Effects of different tillage and straw retention practices on soil aggregates and carbon and nitrogen sequestration in soils of the northwestern China

Soil tillage and straw retention in dryland areas may affect the soil aggregates and the distribution of total organic carbon. The aims of this study were to establish how different tillage and straw retention practices affect the soil aggregates and soil organic carbon(SOC) and total nitrogen(TN) contents in the aggregate fractions based on a long-term(approximately 15 years) field experiment in the semi-arid western Loess Plateau, northwestern China. The experiment included four soil treatments, i.e., conventional tillage with straw removed(T), conventional tillage with straw incorporated(TS), no tillage with straw removed(NT) and no tillage with straw retention(NTS), which were arranged in a complete randomized block design. The wet-sieving method was used to separate four size fractions of aggregates, namely, large macroaggregates(LA, >2000 μm), small macroaggregates(SA, 250–2000 μm), microaggregates(MA, 53–250 μm), and silt and clay(SC, <53 μm). Compared to the conventional tillage practices(including T and TS treatments), the percentages of the macroaggregate fractions(LA and SA) under the conservation tillage practices(including NT and NTS treatments) were increased by 41.2%–56.6%, with the NTS treatment having the greatest effect. For soil layers of 0–5, 5–10 and 10–30 cm, values of the mean weight diameter(MWD) under the TS and NTS treatments were 10.68%, 13.83% and 17.65%, respectively. They were 18.45%, 19.15% and 14.12% higher than those under the T treatment, respectively. The maximum contents of the aggregate-associated SOC and TN were detected in the SA fraction, with the greatest effect being observed for the NTS treatment. The SOC and TN contents were significantly higher under the NTS and TS treatments than under the T treatment. Also, the increases in SOC and TN levels were much higher in the straw-retention plots than in the straw-removed plots. The macroaggregates(including LA and SA fractions) were the major pools for SOC and TN, regardless of tillage practices, storing 3.25–6.81 g C/kg soil and 0.34–0.62 g N/kg soil. Based on the above results, we recommend the NTS treatment as the best option to boost soil aggregates and to reinforce carbon and nitrogen sequestration in soils in the semi-arid western Loess Plateau of northwestern China.

Effects of Carbon and Nitrogen Additions on Soil Microbial Biomass Carbon and Enzyme Activities Under Rice Straw Returning

The effects of different amounts of carbon and nitrogen sources on the soil microbial biomass carbon,dissolved organic carbon and related enzyme activities were studied by the simulation experiment of rice straw returning to the field,and the mechanism of the decomposition of rice straw returning to the field was discussed.Completely randomized experiment of the two factors of the three levels was designed,and a total of nine treatments of indoor soil incubation tests were conducted.Full amount of rice straw was applied to the soil in this simulation experiment and different amounts of brown sugar and urea were added in the three levels of 0(no carbon source and nitrogen source),1(low levels of carbon and nitrogen sources)and 2(high levels of carbon and nitrogen sources),respectively.The results showed that the addition of different amounts of carbon and nitrogen sources to the rice straw could increase the soil carbon content.Compared with T0N0,the microbial biomass carbon of T2N2 was increased significantly by 170.48%;the dissolved organic carbon content of T1N2 was significantly increased by 58.14%and the free humic acid carbon contents of T0N2,T1N1 and T2N0 were significantly increased by 56.16%and 45.55%and 47.80%,respectively;however,there were no significant differences among those of treatments at later incubation periods.The addition of different carbon and nitrogen sources could promote the soil enzyme activities.During the incubation period,all of the soil enzyme activities of adding sugar and urea were higher than those of T0N0 treatment.Therefore,the addition of different amounts of carbon and nitrogen sources to rice straw returning could improve soil microbial biomass carbon content,dissolved organic carbon and soil enzyme activities.

Long-term Decomposition Process of the Leaf Litter, Carbon and Nitrogen Dynamics under Different Forest Management in the Sierra de Francia, Salamanca, Spain

The dynamics of organic matter, carbon and nitrogen were studied during leaf decomposition over a three annual cycles period using the litterbag method at three permanently untilled and unfertilised plots. Our hypothesis is to determine if each litter type influences the decomposition and C and N releases from each other litter type （three plots and two species）. The main objective of this study is the comparison of decomposition dynamics in a climax forest with respect to that occurring in the chestnut managed plots on terrain suitable for oak to have further insight into the recycling of above ground organic matter and these two associated bioelements. As for the loss of dry matter, two-way analysis of variance, involving the treatment and year factors, revealed the existence of significant differences only for year, while no differences were observed for either treatment or interaction. At the end of the 2.4 years of the study, most of the treatment assays higher nitrogen concentrations than the initial ones were recorded. These three treatments the samplings prior to the last one revealed nitrogen concentrations higher than the initial ones, such that it may be concluded that the trend was towards an increase in concentration.

Used for the Study of Nitrogen Fertilizer Slow-Release Carrier Life Sludge

After the sewage treatment, putting the wet sludge in which the heavy metal content is extremely low, corrupt and broken straw, bentonite, urea in proportioning according to the certain ratio, mixing well-distributed, taking the shape of Nitrogen slow-release fertilizers, doing the dynamic bioleaching test by the method of Artificial rainfall simulation, researching the slow-release characteristic, water retention. When the mass ratio of the wet sludge whose water content is 82.5%: bentonite: corrupt and broken straw: urea is 62.5: 12.5: 12.5: 12.5, drip washing the 10g Nitrogen slow-release fertilizers by the 80ml distilled water after 48h, the residue rate of urea is 29.63%; Under the room temperature of 25 ℃, 77%RH, moisture evaporate 46.32% after 60 h. The results demonstrate that the slow-release fertilizer has a good release-effect of nitrogen and water conservation effect. It provides the basic for the development and application of the sewage in the aspect of Nitrogen slow-release fertilizers.

Impact of agricultural intensification on soil organic carbon＂ A study using DNDC in Huantai County, Shandong Province, China

Using the biogeochemical model den itrification/decomposition （DN DC）, the dynamic changes of soil organic carbon （SOC） of farmland from the 1980s to 2030s were investigated in Huantai County, a typical intensive agricultural region in the Huang- Huai-Hai Plain of China. Prior to modelling, validation of the DNDC model against field data sets of SOC from Quzhou Experimental Station in the Huang-Huai-Hai Plain was conducted at the site scale. We compared the simulated results with the observed SOC in Huantai County during 1982-2011 under two different classification methods of simulation unit （the first method integrated soil type and land use of Huantai County to form the overlapped modeling units; the second selected the 11 administrative towns as the modeling units）, and achieved a high accuracy in the model simulation with the improvement of the model parameters. Regional SOC （0-20 cm） density and stocks for Huantai County in the years 2012-2031 were predicted under different scenarios of farming management. Compared with current management practices, optimized fertilization （20% decrease of mineral N）, crop straw incorporation （90%） and appropriate animal manure input （40 kg N ha-1 yr-1） could achieve the highest level of SOC density （56.8% higher than 2011） in the period of 2012-2031. The research highlighted the importance of crop straw incorporation, optimized N fertilization and integration of crop production with ani- mal husbandry on the farmland carbon sequestration for maintaining a high land productivity in the Huang-Huai-Hai Plain.

玉米芯与秸秆作为缓释碳源的改性研究

目的 为解决低C/N污水中碳源不足的问题,探究以玉米芯与秸秆作为固体缓释碳源的可能性。方法 分别使用NaOH溶液、H2O2溶液及NaOH与H2O2的混合液对玉米芯与秸秆进行改性,通过静态试验测定改性后固体碳源的质量变化,分析改性后固体碳源的浸出液中COD、NH_(4)^(+)-N、TN、TP的释放规律,对改性后固体碳源的可生化性能进行研究。结果 经过预处理后的固体碳源释碳能力均有不同程度的提升,经过碱处理组的质量减少最为明显,经过碱处理后的玉米芯具有良好、持久的释碳能力,氮磷的释放量几乎可忽略不计,经过碱处理后的玉米芯和秸秆的可生化性均有所提高,玉米芯的可生化性能增强更明显,更适合微生物的生长繁殖。结论 经过碱性溶液处理后的玉米芯更适于作为固体缓释碳源应用于低C/N污水的脱氮除磷。

氮肥施用和秸秆还田对东北地区褐土稳定性有机碳的影响

为探究长期施用氮肥和秸秆还田措施下农田土壤总有机碳(TOC)的稳定性,以辽宁省国家农业环境阜新观测实验站连续8 a施肥的定位试验田为研究对象,采用有机质酸碱提取和密度分级实验、金属氧化物形态提取实验、碳14定年和次氯酸钠氧化实验等手段,系统研究了长期施用氮肥和秸秆下农田土壤TOC的含量、化学组成及其年龄特征。结果表明:相对于对照组(不施氮肥),单施氮肥处理组的TOC含量降低了5.5%,而氮肥配施秸秆组则升高了2.8%,但两个处理土壤碳氮比均高于对照。随着氮肥和秸秆的加入,土壤有机质酸碱可提取部分的总占比降低,其中胡敏酸从63.6%降低到49.5%,酸碱不可提取部分(即胡敏素)的占比升高(25.9%~39.0%);各处理间土壤TOC的轻、重组分级没有显著差异,均以重组有机碳为主要成分,占TOC的62.3%±0.4%。同时,重组分中可提取的碳和铁铝的比值非常低,表明重组分里的土壤有机质除了与铁铝氧化物结合之外,很可能大部分以团聚或者包被的形式与黏土结合。碳14定年结果显示,3个处理组中土壤的年龄在距今2000 a左右,试验区农田土壤以长期稳定有机碳为主。研究表明,氮肥施用和秸秆还田向土壤中增加新有机碳,增加了土壤中矿质结合的胡敏素类有机质;而所产生的激发效应导致土壤中部分原有的稳定有机碳降解,减少了腐植酸类有机质。新增有机碳的不稳定性及激发效应导致的原有稳定有机碳的降解,制约了氮肥施用和秸秆还田对土壤TOC累积的贡献。

耕作和秸秆还田对球囊霉素和土壤生态化学计量特征的影响

为探究耕作与秸秆还田对土壤球囊霉素相关蛋白含量、生态化学计量特征以及两者之间关系的影响,本研究选择长期进行作物生产的农场土壤,采集免耕、耕作和耕作秸秆还田三种处理下的0~20 cm土层土壤样品进行分析。结果表明,免耕土壤总球囊霉素含量为4.1 mg/g,较耕作土壤显著提高5.1%,耕作秸秆还田土壤较耕作土壤提高3.6%,免耕和耕作秸秆还田土壤易提取球囊霉素含量分别较耕作土壤提高4.8%和6.1%。免耕和耕作秸秆还田土壤有机碳含量分别为17.58、17.89 mg/g,较耕作土壤显著提高14.1%、16.1%;免耕土壤全氮含量为1.49 mg/g,较耕作和耕作秸秆还田土壤分别显著提高26.3%、17.3%。耕作秸秆还田土壤碳氮比达到14.47,显著高出免耕土壤33.2%。方差分解分析及线性相关分析表明,土壤有机碳、全氮含量影响球囊霉素的分泌和释放,免耕和耕作秸秆还田有利于提高土壤有机碳、全氮含量,从而促进球囊霉素的分泌,而长期耕作对丛枝菌根真菌分泌土壤球囊霉素具有限制作用。

秸秆施用下减施氮肥稻田有机碳和氮磷的排放特征

为了解秸秆施用下减施氮肥对稻田有机碳和氮磷排放特征的影响,进而为稻田投入品的优化施用以及田间养分管理提供技术支撑,通过盆钵试验研究小麦秸秆还田与肥料施用对高砂土和黄泥土2种土壤的田面水有机碳和氮磷浓度、潜在可排放量及水稻产量的影响。结果表明,高砂土稻田的田面径流养分排放风险远大于黄泥土,其中基肥期更为明显;磷在基肥期田面径流中的排放风险最大,施加秸秆处理的有机碳在蘖肥期田面径流中的排放风险最大,而氮在穗肥期的排放风险最大;无论高砂土还是黄泥土,秸秆施用基础上,相比施用常量氮肥,施用减量氮肥在保证产量不受明显影响的同时,可以有效降低田面径流养分排放风险。在小麦秸秆还田条件下,施用减量氮肥与常量氮肥相比,高砂土稻田田面水的COD、DOC、TN和TP平均可排放量分别降低34.92%、15.47%、35.37%和53.93%,水稻产量降低12.01%,黄泥土稻田田面水的COD、TN和TP平均可排放量分别降低24.82%、23.75%、2.84%,而水稻产量提高3.99%。总之,秸秆还田时减施氮肥利于降低高砂土和黄泥土田面水COD、TN、NH_(4)^(+)-N和NO_(3)^(-)-N的潜在排放风险,以稳定水稻产量和防控稻田养分田面径流流失为目标,高砂土稻田在水稻种植时氮肥施用应减量多次,并避免小麦秸秆还田,而黄泥土稻田在氮肥施用时应混施秸秆。

不同耕作及秸秆还田方式对土壤养分及微生物生物量碳氮的影响

为促进作物稳产增产,采用田间定位试验,研究不同耕作[免耕(NT)、浅耕(ST)、深耕(DT)]及秸秆还田方式[秸秆还田(-T)、秸秆离田]下,黑土区土壤剖面(0~10 cm、10~20 cm、20~30 cm、30~40 cm)养分及微生物量碳、微生物量氮的变化。结果表明,不同耕作方式处理的土壤理化性质存在显著差异,在各耕层中土壤有机质含量最高的处理依次为NT-T、DT、ST-T和DT;全氮含量最高的处理依次为ST-T、DT、NT-T和NT-T;速效氮含量最高的处理依次为DT-T、DT-T、DT和NT;土壤各耕层pH均为ST处理最高;土壤含水率在0~10 cm土层中NT-T处理最高,其他土层中均为ST-T处理显著高于其他处理;土壤微生物生物量碳、氮含量均表现为ST-T处理最高。不同的耕作方式下,土壤有机质、速效氮、含水率在秸秆还田方式下表现最高;而土壤微生物生物量碳氮含量无论在秸秆是否还田下,浅耕和深耕的方式均优于免耕。

秸秆还田下氮肥水平对秸秆碳固定及土壤有机碳储量的影响

土壤有机碳(SOC)库在养分循环和缓解全球温室效应方面起重要作用。为了探究氮肥对秸秆碳在土壤中的转化以及SOC库的影响,本研究采用盆栽试验,向不同施氮水平[0 kg(N)∙hm^(-2)(N0)、120 kg(N)∙hm^(-2)(N120)、240 kg(N)∙hm^(-2)(N240)、360 kg(N)∙hm^(-2)(N360)]的稻田土壤中添加^(13)C标记的小麦秸秆,在水稻成熟后采集土样测定不同碳组分含量以及δ^(13)C值,并分析土壤微生物群落组成。研究结果显示,与N0处理相比,N240和N360处理中SOC显著提高7.8%和7.4%,全氮显著提高37.2%和34.3%,溶解性有机碳显著提高33.7%和48.6%,微生物量碳显著提高97.9%和89.6%;但土壤碳氮比显著降低21.6%和20.0%。相比N0处理,N120处理的SOC、全氮、碳氮比和溶解性有机碳并没有显著差异,但显著提高微生物量碳的含量。此外,秸秆还田条件下施用氮肥使细菌含量显著提高24.7%~55.4%,真菌含量显著提高18.3%~30.2%,总磷脂脂肪酸含量显著提高18.1%~45.2%。施用氮肥提高>2000μm和250~2000μm团聚体的占比以及游离态颗粒有机碳(fPOC)和微团聚内颗粒有机碳(iPOC)组分的有机碳储量,同时分别显著增加了fPOC和iPOC组分中δ^(13)C值128.3%~194.8%和105.6%~216.9%。但是在高氮(N360)处理下,除fPOC组分外,其他各有机碳组分储量未持续增加。结构方程表明,施用氮肥可通过增加溶解性有机碳含量,增加土壤中fPOC组分中有机碳储量,或者促进微生物群落活性增加iPOC组分中有机碳储量来提高SOC含量。本研究结果表明,秸秆还田条件下施用适量氮肥能够促进秸秆碳在土壤中的固定并且增加SOC含量。

秸秆还田配施氮肥对黑土玉米田土壤CO_(2)排放与碳平衡的影响

为探寻不同秸秆还田方式配施氮肥对黑土玉米田土壤CO_(2)排放与碳平衡的影响,于2023年开展大田试验,设置秸秆离田(S0,对照)、秸秆覆盖还田(S1)、秸秆旋耕还田(S2)3种秸秆还田方式,同时设置常规施加氮肥(N,250kg/hm^(2))与不施加氮肥(W,0kg/hm^(2),对照)2种施氮模式,共计6个处理。测定不同处理下玉米生育期土壤CO_(2)排放通量以及玉米收获后土壤有机碳(SOC)、可溶性有机碳(DOC)、微生物量碳(MBC)含量,探究土壤CO_(2)累积排放量与SOC、DOC、MBC含量的关系,并分析黑土玉米田生态系统碳平衡状况。结果表明:各处理中土壤CO_(2)累积排放量从大到小依次为S2N、S1N、S0N、S2W、S1W、S0W,其中S2N处理土壤CO_(2)累积排放量较S0W处理显著增加70.31%(P<0.05)。在相同施氮模式下,秸秆还田能够有效增加SOC、DOC、MBC含量,且土壤CO_(2)累积排放量与SOC、DOC、MBC含量呈正相关关系。不同秸秆还田方式配施氮肥下,S1N处理玉米产量最高,为13534.4kg/hm^(2),作物碳排放速率最低,为0.122kg/kg。不同秸秆还田方式配施氮肥下黑土玉米田生态系统碳平衡值均为正值,表现为较强的碳“汇”,其中S1N处理碳平衡值和土壤固碳潜力最大,较其他处理分别增加13.12%~94.05%、3.49%~25.32%。综上所述,在本试验条件下,秸秆覆盖还田+常规施氮(S1N处理)可以实现黑土玉米田土壤固碳减排和作物增产目的。

改性聚丙烯基缓释碳源耦合生物膜水质净化器的脱氮效能研究

固态缓释碳源逐渐成为提高低碳氮比(C/N)污水脱氮效能的有效方法。本研究制备了一种新型亲水改性多孔聚丙烯基缓释碳源材料(HEPP-C),并利用其作为生物填料构建生物膜水质净化器,对低C/N污水脱氮效能进行研究。结果表明:HEPP-C能够稳定持久地释碳;在间歇反硝化体系中,HEPP-C具有最高的脱氮效率,对NO_(3)^(-)-N和TN的去除率分别为89.6%和89.5%;连续流缓释碳源耦合生物膜净化体系中,HEPP-C缓释碳源能够显著提高NO_(3)^(-)-N和TN的去除效率,当进水NO_(3)^(-)-N含量低于20 mg/L、水力停留时间为12 h、曝气—停曝时间为8 h—4 h时,出水TN浓度为1.24 mg/L,低于地表水Ⅵ类水质标准值。可见,构建的HEPP-C基缓释碳源耦合生物膜水质净化器能够对低污染污水以及河湖水体实现有效脱氮。

长期秸秆还田对褐土农田土壤有机碳、氮组分及玉米产量的影响

基于1992—2022年连续30 a的长期定位试验,研究秸秆不还田(CK)、秸秆覆盖还田(SM)、秸秆粉碎直接还田(SC)和秸秆过腹还田(CM)4种不同秸秆还田方式对土壤有机碳、氮组分和作物产量的影响。结果表明:(1)不同秸秆还田方式均可增加耕层土壤有机碳、全氮及其组分含量;与CK相比,CM处理0~20 cm土层土壤的总有机碳(SOC)、轻组有机碳(LFOC)、微生物量碳(MBC)、水溶性有机碳(DOC)和颗粒有机碳(POC)的含量分别显著增加42.85%、93.51%、80.09%、190.42%和123.38%;土壤全氮(TN)、轻组有机氮(LFON)、微生物量氮(MBN)、水溶性有机氮(WSON)和颗粒有机氮(PON)的含量分别显著增加49.37%、34.26%、69.49%、172.73%和129.29%。(2)各活性有机碳组分与土壤有机碳的比值表现为LFOC>POC>MBC>DOC;各氮组分与土壤全氮的比值表现为LFON>PON>MBN>WSON。(3)CM和SC处理下敏感指数最高的指标为DOC,DOC可作为CM和SC处理早期有机物变化的指示物;SM处理下敏感指数最高的指标为LFOC,LFOC可作为SM处理早期有机物变化的指示物。(4)土壤有机碳、氮组分间均呈显著正相关关系,其中DOC可以较好地反映SOC的变化情况,WSON可较好地反映TN的变化情况。(5)与CK相比,长期秸秆还田均可以显著提高玉米产量,SM、SC和CM处理30 a累计产量分别增加6.38%、7.82%和23.00%。综上,长期秸秆还田是提高土壤有机碳氮组分含量和作物产量的有效耕作措施,以秸秆过腹还田效果最为突出,可在黄土高原旱地玉米种植区域推广。

秸秆还田和水旱轮作模式对稻季土壤温室气体排放的影响

【目的】探究不同水旱轮作模式下,冬季作物秸秆还田对后茬水稻季作物产量和温室气体排放的影响,为长江中游稻田选择适宜的秸秆还田方式和农业可持续生产提供科学依据。【方法】田间试验在湖北荆州进行,设置水稻–小麦(稻麦)、水稻–油菜(稻油)和水稻–紫云英(稻肥)3种水旱轮作模式,每个模式下设置冬季作物收获后秸秆还田和不还田处理。在秸秆还田后的水稻季,采用静态暗箱—气相色谱法连续监测稻田中甲烷(CH_(4))和氧化亚氮(N_(2)O)排放量,在水稻分蘖期、抽穗期、成熟期采集0—5、5—10、10—20 cm土层样品,测定微生物量碳(MBC)、可溶性有机碳(DOC)、铵态氮(NH_(4)^(+)-N)和硝态氮(NO_(3)^(-)-N)含量,收获期测定水稻产量。【结果】秸秆还田和不同轮作模式对后茬水稻产量均无显著影响。与稻肥轮作相比,在秸秆还田条件下稻油和稻麦轮作水稻季土壤CH_(4)和N_(2)O排放分别高出44%~58%和17%~30%,在秸秆不还田条件下则分别高出58%~72%和15%~22%。与秸秆不还田相比,秸秆还田条件下3种轮作模式平均CH_(4)和N_(2)O排放分别增加26%~39%和20%~29%。秸秆还田条件下,稻油和稻麦轮作稻季土壤全球增温潜势(GWP)和温室气体排放强度(GHGI)分别比稻肥轮作高出14%~19%和12%~19%,秸秆不还田条件下分别高出18%~23%和15%~24%。与秸秆不还田相比,秸秆还田条件下3种轮作模式稻季土壤平均GWP和GHGI高出31%和32%,同时土壤硝态氮、微生物量碳和可溶性有机碳含量均显著提高。此外,稻麦轮作土壤微生物量碳和可溶性有机碳含量显著高于稻肥、稻油轮作。相关性分析表明,秸秆还田条件下,CH_(4)和N_(2)O排放与NO_(3)^(-)-N呈极显著正相关(P<0.01),而秸秆不还田条件下CH_(4)排放与NO_(3)^(-)-N呈极显著正相关(P<0.01),N_(2)O排放与NH_(4)^(+)-N呈极显著正相关(P<0.01)。【结论】水稻季土壤CH_(4)和N_(2)O的排放与土壤可利用性碳氮浓度的升高密切相关。前茬作物秸秆还田导致水稻季温室气体排放显著增加,与稻麦、稻油轮作相比,水稻–紫云英轮作稻季土壤的温室气体排放量最低,是较为生态环境友好型的种植制度。

缓释碳源应用于低碳氮比污水脱氮研究进展

处理低碳氮比(C/N)污水时,生物法脱氮反硝化进程中碳源不足易导致脱氮效率偏低,需通过额外投加碳源进行补偿。外加碳源在污水脱氮过程中应用广泛,其投加量不易控制的缺陷可以通过利用缓释技术进行弥补。归纳了碳源缓释的特点及其在低C/N污水处理中的应用现状,总结了固体缓释碳源的不同类型及其在生物反硝化脱氮中的强化效果,对比分析不同缓释碳源在脱氮方面的优缺点。提出了目前缓释碳源应用的局限性,并对缓释碳源在生物反硝化脱氮领域的发展方向进行了展望。

水稻秸秆炭施用对水稻土团聚体稳定性及其碳氮分布的影响

[目的]水稻长期种植过程中大量化肥施用导致土壤结构变差,研究不同用量水稻秸秆生物炭和化肥配施对水稻土结构和碳、氮分布的影响,探索稻田优化施肥管理方式。[方法]水稻田间试验在浙江衢州进行,试验设不施肥对照(CK)、常规施肥处理(NPK)以及常规施肥基础上添加22.5 t/hm^(2)(NPK+1%B)、45 t/hm(NPK+2%B)和90 t/hm^(2)(NPK+4%B)水稻秸秆炭处理,共5个处理。水稻收获后采集0-20 cm土层样品,测定土壤及不同粒级团聚体(>2、0.25~2、0.053~0.25和<0.053 mm)的有机碳和全氮含量,评价团聚体的稳定性。[结果]与NPK处理相比,施用水稻秸秆炭4年后,土壤>0.25 mm粒级团聚体含量提高了2.43%~7.99%,<0.25 mm粒级团聚体含量降低了2.93%~9.63%,土壤有机碳和全氮含量分别提高了16.40%~45.16%和14.67%~36.69%,各指标的变幅均以NPK+4%B处理最大。与NPK处理相比,秸秆炭处理土壤中>2 mm粒级团聚体中的有机碳和全氮含量分别提高了23.96%~70.87%和19.44%~47.56%,0.25~2 mm粒级团聚体中分别提高了21.87%~49.27%和17.18%~37.47%,增幅均以NPK+4%B处理最高,而0.053~0.25和<0.053 mm粒级团聚体中的有机碳和全氮含量无显著差异(P>0.05),说明施用水稻秸秆炭4年后,增加的土壤有机碳和全氮主要积累在>0.25 mm粒级团聚体中。与NPK处理相比,秸秆炭处理水稻土C/N值提高了2.40%~5.69%,但各处理间差异不显著,而4个粒级团聚体的土壤C/N值均显著提升,且均以NPK+4%B处理提高效果最好。此外,施用水稻秸秆炭提高了>2和0.25~2 mm粒级团聚体的碳、氮贡献率6.54%~17.43%、3.67%~7.28%和5.16%~11.55%、0.57%~1.83%,降低了0.053~0.25和<0.053 mm粒级团聚体的碳、氮贡献率7.25%~29.27%、15.93%~33.68%和10.26%~26.80%、12.61%~30.78%(P<0.05)。[结论]施用水稻秸秆炭能够迅速显著提高水稻土有机碳和全氮含量,增加>0.25 mm粒级团聚体质量占比,提高>2 mm粒级团聚体中有机碳的贡献率,降低<0.25 mm粒级团聚体中有机碳和全氮贡献率,且其影响幅度与水稻秸秆炭施用量呈正比。由此可见,施用水稻秸秆炭能在一定程度上改善水稻土结构,提高水稻土碳、氮固持潜力,对保证水稻土结构稳定性和维持水稻持续高产具有重要意义。