不同培肥措施对藏东南土壤酶活性的影响

对进行不同培肥措施后土壤进行理化性状和酶活性测定 ,结果表明 :土壤中的脲酶、转化酶、碱性磷酸酶活性与土壤肥力有良好的相关性。不同培肥措施中 ,以有机肥 (厩肥、秸秆 )配施化肥对脲酶、转化酶、碱性磷酸酶活性影响最大 ,分别是单施化肥处理的酶活性的 1 .47、3 .3 1、1 .0 7倍。各培肥措施中 ,以有机肥 (厩肥、秸秆 )配施化肥效果最好 ,有机无机结合中厩肥 化肥又优于秸秆 化肥。建议藏东南地区采用有机无机结合方式培肥土壤。     

长期施肥潮土在玉米季施肥初期的有机碳矿化过程研究

以黄淮海平原长期定位试验地2007年玉米播种期土壤为研究对象,通过室内37天的培养实验并选择4个应用比较广泛的方程对土壤有机碳矿化过程进行拟合,其目的主要是为了比较研究长期不同施肥土壤在玉米季施肥初期有机碳矿化过程及主要矿化参数的差异,并评估矿化参数和主要土壤性质之间的相关关系.结果表明,37天培养期内各施肥处理土壤CO2-C累积释放量与土壤有机碳、全氮含量和微生物活度均呈显著正相关,大小依次为OM＞1/2OM+1/2NPK＞NPK＞NP＞PK＞CK＞NK,有机碳矿化过程均呈曲线形式,与Jones(1984)改进的一级动力学方程拟合效果最好.拟合所得土壤潜在可矿化有机碳量(C0)、易矿化有机碳量(C1)和初始潜在矿化速率(C0k)均表现出有机肥处理高于化肥处理,施肥处理高于不施肥处理(NK处理除外),与土壤有机碳、全氮和土壤微生物活度均呈显著正相关;有机碳矿化速率(k)和土壤潜在可矿化有机碳占土壤总有机碳的比例在处理间差异均不显著,除k与有机碳呈显著负相关外,其他与土壤性质均无显著相关性.因此,我们推测有机肥和化肥的平衡施用均能显著增强土壤有机碳的矿化作用,有利于土壤无机养分的释放,同时使部分有机碳在土壤中积累.     

长期不同比例有机肥-化肥配施下红壤性水稻土氮素矿化特征

土壤有机氮的矿化是土壤氮素肥力的重要指标之一,也是影响作物产量至关重要的因素。以33年长期定位试验为依托,对红壤性双季稻田土壤氮累积、矿化动力学特征等进行系统研究。定位试验始于1984年,选取其中5个施肥处理:不施肥(CK),施氮磷钾肥(NPK),施50%化肥+50%有机肥(50F+50M),施30%化肥+70%有机肥(30F+70M),施70%化肥+30%有机肥(70F+30M),于2017年早稻种植前采集耕层(0～20 cm)土壤样品,采用淹水密闭间歇淋洗法,对土壤氮矿化量和速率进行测定,并采用一级动力学方程拟合土壤氮矿化势(N_0)、矿化速率常数(k)等。结果表明,长期施肥显著提高土壤有机碳、全氮、碱解氮含量,以有机无机肥配施提升效果最为显著,且随有机肥投入量增加而递增,30F+70M处理较NPK处理显著提高铵态氮、硝态氮及总矿质氮含量,分别提高了47.0%、64.6%和49.7%。连续施肥33年后,施肥显著提高了土壤净矿化速率和土壤矿化氮释放量,排序为30F+70M50F+50M70F+30MNPKCK,配施有机肥较施化肥处理显著提高了土壤矿化氮累积释放量和土壤氮素矿化率,分别是化肥处理的2.70和1.41倍。长期施肥均显著提高了土壤氮素矿化势(N_0),提高幅度为65.9%～196.0%,配施30%有机肥(70F+30M)较施化肥处理(NPK)可显著增加水稻土氮素矿化势,降低氮矿化速率常数。土壤有机质、全氮、碱解氮及铵态氮含量显著影响N_0、N_0/N、累积矿化量及矿化率,土壤氮矿化速率常数(k)与C/N呈现极显著负相关。长期化学氮肥与低比例有机肥配施,使水稻土供氮缓慢而持久,在水稻的生长发育过程中能够不断地补充氮素。     

长期施肥对黑土呼吸过程的影响

土壤呼吸是土壤有机C矿化分解,释放无机养分的重要生物化学过程。对公主岭地区长期有机肥(不施有机肥、施中量和高量有机肥处理)与化肥(不施化肥、施用N、NP、NPK化肥)配合施用的12个处理的黑土进行室内好气培养(196天),采用一级动力学方程模拟土壤的呼吸过程,结果表明,有机肥和化肥的施用能显著增加土壤呼吸释放的CO2 -C的累积量,提高土壤中潜在矿化的有机碳含量及其占土壤有机质的比例,促进土壤有机质中无机养分的释放,有利于提高土壤养分的有效性,改善黑土的供肥状况。有机肥与NPK化肥配合施用效果更为明显。     

不同培肥措施对河套灌区盐碱地改良效果

为了研究不同培肥措施对盐碱化土壤改良效果,以内蒙古河套灌区盐碱地为对象,通过3年田间试验,研究了等氮素条件下不同培肥措施对土壤pH值、全盐、脱盐率、有机质、全氮、碱解氮、有效磷等指标的影响。结果表明:不同培肥措施土壤剖面盐分变化趋势基本一致,即0～20 cm降低,20～60 cm升高,60～100 cm稳定,其中CK、化肥处理表层土壤(0～20 cm)盐分含量最高,收获期土壤盐分分别为5.33和5.24 g·kg~(-1);秸秆还田、秸秆还田+有机肥、秸秆还田+有机肥+化肥配施处理盐分含量最低,收获期土壤盐分分别为5.0、4.58、4.73 g·kg~(-1)。不同培肥措施0～10、10～20 cm土壤脱盐率分别为7.81%～20.70%、4.48%～16.96%,其中有机肥、秸秆还田与有机肥、秸秆还田+有机肥+化肥配施对促进盐分淋洗、抑制反盐的效果较好,土壤脱盐率分别为11.99%、18.83%、15.65%,以CK和单施化肥处理效果最差,分别为5.74%、6.37%。作物生育期内,不同培肥措施的土壤pH值变化差异不显著,但连续施用有机肥、有机肥+秸秆以及有机肥+秸秆还田+化肥配施耕层土壤pH值较CK处理降幅较大。与CK相比,不同培肥措施均显著提高耕层土壤碱解氮、有效磷的含量(P 0.05),其含量分别提高29.43%～93.14%、17.45%～161.84%;有机肥、有机肥与化肥配施显著提高了土壤有机质和全氮的含量,分别为14.66%、13.36%和13.36%、17.35%。有机肥、秸秆还田、化肥三者配施均能显著提高向日葵产量,其中有机肥+秸秆还田+化肥处理对向日葵产量提高的最为显著,较CK增产44.41%。因此,在等氮素条件下,河套灌区应重视有机肥与化肥、有机肥与秸秆还田、有机肥与秸秆还田+化肥的配合施用,不仅可以培肥土壤、提高脱盐率,还可获得一定的高产。     

施用不同有机物料对棕壤酶活性的影响

为研究施用不同有机物料对棕壤酶活性的影响,在昌图棕壤试验地上设6个处理,测定不同培肥方式下土壤酶活性,并研究了土壤酶与土壤肥力因子的相关关系。结果表明:(1)秸秆还田和施用厩肥均能显著提高土壤酶活性和纤维素分解强度。在提高脲酶、转化酶活性方面施用厩肥效果好于秸秆还田,全量施用优于半量施用;在提高酸性磷酸酶、过氧化氢酶方面秸秆还田效果好于施用厩肥。各处理中,秸秆还田配施厩肥对提高脲酶活性效果最好,对提高其他各类酶活性效果一般。除过氧化氢酶外,其他各类酶活性均随着土层深度的增加而降低。(2)各种土壤酶之间存在一定的相关关系。脲酶与转化酶呈极显著正相关关系(r=0.913**);转化酶与磷酸酶呈极显著负相关(r=-0.643**);磷酸酶与过氧化氢酶呈极显著正相关关系(r=0.639**)。土壤酶与其他肥力因子之间也具有一定的相关关系。土壤脲酶与纤维素分解强度、碱解氮、速效磷、速效钾、有机质、含水量均达到极显著正相关关系(r分别为0.906**、0.821**、0.911**、0.917**、0.888**、0.867**);土壤转化酶与纤维素分解强度、碱解氮、速效磷、速效钾、有机质、含水量均达到极显著正相关关系(r分别为0.958**、0.857**、0.855**、0.842**、0.820**、0.831**);土壤酸性磷酸酶与含水量呈极显著负相关关系(r=-0.666**),与土壤容重呈显著负相关(r=-0.560*);土壤过氧化氢酶与土壤容重呈极显著负相关(r=-0.765**)。     

不同培肥管理措施对土壤微生物生态特征的影响

本文研究了厩肥区、秸杆区、化肥区和无肥对照区四种不同培肥管理措施对土壤微生物生态特征的影响,结果表明,施入厩肥、化肥或秸杆还田均能明显增加土壤微生物生物量及呼吸量;土壤微生物生物质量、土壤呼吸及代谢商等微生物指标均与土壤有机质的变化呈相同的变化趋势;BIOLOG生态盘测试亦揭示了培肥管理措施能明显影响土壤微生物的群落结构。     

不同施肥处理红壤生物活性有机碳变化及与有机碳组分的关系

采用物理分组方法对长期不同施肥处理的旱地红壤有机碳组分进行了区分,布置室内培育试验观测了培养过程中土壤有机碳的矿化动态,通过拟合一级动力学方程计算土壤生物活性有机碳库量.研究结果表明,不同施肥处理的土壤中,轻组有机碳(LF-C)、团聚体包裹的粗颗粒有机碳(iPOMc-C)及细颗粒有机碳(iPOMf-C)、矿物结合态有机碳(mSOC)分别占总有机碳的7%～10%、0.5%～1.5%、4%～7%、76%～85%,并与总有机碳(TOC)含量显著相关;厩肥处理显著增加了各组分含量,其作用优于绿肥处理和单施无机肥处理(CK);培养过程中土壤有机碳矿化动态符合一级反应动力学方程;有机无机肥配施处理的土壤生物活性有机碳库(C0)显著提高;和绿肥相比,厩肥处理中生物活性有效碳库(C0)增加幅度更大,但其周转速率常数k更小;各组分有机碳含量与C0含量均达到极显著(p＜0.01)相关,但除LF-C外其余有机碳组分占TOC的百分率均与C0达到极显著水平.     

不同培肥措施对银北灌区土壤盐碱特性、玉米生长及产量指标的影响

为探究银北灌区盐碱地不同培肥措施下的土壤盐碱特性和作物生长情况，通过3年定位试验开展了不同量化肥、秸秆、生物有机肥应用后对土壤盐碱特性、春玉米生长及产量指标的影响研究。结果表明:(1)玉米播前土壤表现为对照脱盐碱化现象最明显，而高量生物有机肥和高量化肥有增加耕层土壤盐分含量的趋势，秸秆还田在降低玉米生长前期耕层土壤pH值方面较显著；(2)高量秸秆还田在提高玉米株高和增加玉米茎粗方面优于施用生物有机肥和中低量化肥，玉米株高、茎粗随着有机肥和秸秆用量的增加而提高；(3)在增加玉米穗长、穗粗和穗粒重方面，单施化肥措施优于单施秸秆或生物有机肥；在增加玉米百粒重方面，秸秆还田与化肥措施效果相当；培肥第3年各处理玉米产量表现为:施用生物有机肥T4>T3>T2，施用秸秆T6>T7=T5，施用化肥T10>T9>T8，配施处理T11>T12，玉米产量随生物有机肥和化肥施用量的增加而提高，秸秆还田在提高玉米产量方面优于生物有机肥，而中量秸秆还田在提高玉米产量方面优于高量和低量秸秆还田。与施用化肥相比，试验区连续3年配施生物有机肥在提高玉米产量方面已表现出优势，而配施秸秆在提高玉米产量方面尚未发挥优势，秸秆还田相对生物有机肥在提高作物产量方面存在滞后效应。     

硅基膜材缓控释肥在红壤中的氮素释放特征研究

通过土壤培养法和饱和盐溶液蒸汽压法,研究硅基膜材缓控释肥在不同土壤温度、含水量和水蒸汽压条件下的氮素释放特性,探讨土壤温度、含水量和水蒸汽压因素对其氮素释放的影响,阐述其在红壤中的控释机制。结果表明:硅基膜材缓控释肥在红壤中的氮素释放速率均随土壤温度、水分含量和水蒸汽压升高而明显提高,其中温度是主要影响因素。不同条件下,包膜肥料的氮素释放率随培养时间的变化均符合一级动力学方程。包膜尿素在15、25、40 和60℃的红壤中,氮素累积释放率达80% 所需要的时间分别为140、110、25 和10 d。土壤含水量为10% 时,养分释放受抑制;当土壤含水量由20% 上升至40%,养分释放速率加快,释放期缩短20 d。养分释放速率常数k 随水蒸汽压差的增大而增加;相同培养时间内,氮素累积释放率H2O>KH2PO4 饱和溶液>KCl 饱和溶液。土壤温度和含水量均通过改变包膜内外水蒸汽压而影响养分释放速率。在实际应用过程中,致使硅基膜材缓控释肥膜内外水蒸汽压变化的因素,均对其养分释放速率产生影响。     

不同管理措施对滨海盐渍农田土壤CO2排放及碳平衡的影响

为探讨不同管理措施对滨海盐渍农田碳平衡的影响,本文通过玉米–小麦轮作试验,研究农田土壤的CO_2释放规律,及其农田碳收支状况。试验设计6个处理:1常规对照(CK);2有机肥常量(OF);3氮肥增施(NF);4秸秆还田(S);5有机肥加秸秆(OF+S);6免耕(NT)。研究表明,秸秆还田和有机肥的施用增加了土壤呼吸的强度,而免耕处理的CO_2平均释放量最低,不同处理下土壤呼吸总体表现为OF+SSOMNFCKNT。各处理土壤有机碳含量随着作物的收获逐渐升高,其中OF与NT增加最多,而增施氮肥处理并没有显著提高土壤的有机碳水平。各处理间的有机碳含量没有显著性差异。在两季作物种植结束后,各处理的碳输入均高于碳输出,均为碳净输入,表现出较强的碳汇特征。秸秆还田和单施有机肥的碳净输入均显著高于对照,可有效减缓因农田土壤CO_2排放而造成的全球气候变化问题。     

Long-term application of organic manure and nitrogen fertilizer on N2O emissions, soil quality and crop production in a sandy loam soil

A long-term field experiment was established to determine the influence of mineral fertilizer (NPK) or organic manure (composed of wheat straw, oil cake and cottonseed cake) on soil fertility. A tract of calcareous fluvo-aquic soil (aquic inceptisol) in the Fengqiu State Key Experimental Station for Ecological Agriculture (Fengqiu county, Henan province, China) was fertilized beginning in September 1989 and N₂O emissions were examined during the maize and wheat growth seasons of 2002-2003. The study involved seven treatments: organic manure (OM), half-organic manure plus half-fertilizer N (1/2 OMN), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer PK (PK) and control (CK). Manured soils had higher organic C and N contents, but lower pH and bulk densities than soils receiving the various mineralized fertilizers especially those lacking P, indicating that long-term application of manures could efficiently prevent the leaching of applied N from and increase N content in the plowed layer. The application of manures and fertilizers at a rate of 300 kg N ha⁻¹ year⁻¹ significantly increased N₂O emissions from 150 g N₂O-N ha⁻¹ year⁻¹ in the CK treatment soil to 856 g N₂O-N ha⁻¹ year⁻¹ in the OM treatment soil; however, there was no significant difference between the effect of fertilizer and manure on N₂O emission. More N₂O was released during the 102-day maize growth season than during the 236-day wheat growth season in the N-fertilized soils but not in N-unfertilized soils. N₂O emission was significantly affected by soil moisture during the maize growth season and by soil temperature during the wheat growth season. In sum, this study showed that manure added to a soil tested did not result in greater N₂O emission than treatment with a N-containing fertilizer, but did confer greater benefits for soil fertility and the environment.     

灌淤土区长期施钾对作物产量与养分及土壤钾素的长期效应研究

通过在宁夏灌淤土区长达14年的连续施钾和小麦秸秆还田试验, 研究钾素投入对作物产量、养分和土壤钾素状况的影响.结果表明:小麦秸秆还田和长期施用钾肥均可不同程度提高小麦和玉米的经济产量, 其中施钾年平均增产小麦244 kg·hm-2, 玉米397 kg·hm-2, 处理之间产量表现为氮磷钾肥配合秸秆还田>施用氮磷钾肥>氮磷肥配合秸秆还田>只施用氮磷肥.定位后8～10年施钾肥开始显著有效, 玉米显效时间早于小麦;秸秆还田和钾肥的投入均可提高籽粒和秸秆的钾素吸收量, 秸秆含钾丰富, 籽粒钾含量仅占植株钾总量的13%～17%;施用钾肥可提高作物籽粒大中微量元素含量而降低秸秆中、微量元素含量, 促进籽粒对大部分元素的吸收;长期不施钾肥处理(NP和NP+St)0～20 cm土层土壤速效钾和缓效钾含量较定位开始时下降; 所有处理土壤全钾含量均表现下降, 下降幅度为0.8～1.2 g·kg-1.     

Soil Carbon Dioxide Emissions from Sorghum–Sunflower Rotation in Rainfed Semi-arid Tropical Alfisols: Effects of Fertilization Rate and Legume Biomass Incorporation

The long-term effects of plant legume [horse gram (Macrotyloma uniflorum)] biomass incorporations were assessed in terms of carbon dioxide (CO₂) emissions, soil quality parameters, and climatically influenced soil parameters in a dryland Alfisol under varying soil fertility conditions. Six selected treatments consisted of off-season legume incorporation (I) and no incorporation?/?fallow (F), each under three varying nitrogen and phosphorus fertilizer levels (viz., N₀P₀, N₂₅P₃₀, and N₅₀P₃₀). Soil moisture, soil temperature, soil surface carbon dioxide emission, soil dehydrogenases, and microbial biomass carbon (MBC) were monitored at three different crop situations [viz., Kharif period (KP), legume/fallow period (LP), and no crop period (NP)] at 14 different periods of the year. Incorporation practices resulted in greater rates of CO₂ emission over fallow conditions during the Kharif and legume periods, whereas the emission rate was greater in fallow soils during the end of the legume and no crop periods. The increased rates of fertilizer doses also significantly increased the soil CO₂ flux during the majority of the measurements. Beneficial effects of incorporation practices were observed in terms of high soil moisture (5–11%), low soil temperature (3–7%), and high content of MBC over without incorporations. Correlation studies indicated that the soil property MBC was found to be the greatest significant variable with CO₂ emission in all the fertilizer treatments under biomass-incorporated soils. These results indicated the undesirable (in terms of CO₂ fluxes) and desirable (soil biological and other parameters) effects of legume biomass incorporation and fertilizer application and their significance in improving soil quality and greenhouse gas (GHG) emissions in dryland Alfisols of semi-arid tropics.     

不同秸秆还田年限对稻麦轮作系统温室气体排放的影响

为揭示稻麦轮作系统不同秸秆还田年限下温室气体排放特征及减排调控机制,本研究采用大田小区试验,考察了稻麦轮作不同秸秆还田年限[空白对照(CK)、常规处理秸秆不还田(NT)、1年秸秆还田(SR1)和5年秸秆还田(SR5)]对CH4、CO2和N2O 3种温室气体排放规律的影响,同时测定了土壤固碳量,估算了秸秆焚烧产生的温室气体排放量,综合计算了4种处理对全球变暖的贡献。试验结果表明,SR1和SR5均显著提升CH4和CO2的排放通量,分别高出NT、CK处理73.52%、309.49%和13.29%、13.06%;同时显著降低N2O排放通量,较NT降低29.68%和42.55%;但SR1和SR5之间温室气体排放通量差异不显著;与NT相比,SR1和SR5可以显著提高土壤固碳量517.9%和709.03%,SR5土壤固碳量高出SR1达30.93%;NT秸秆焚烧产生的全球气温变暖贡献为9 698.49 kg(CO2-eqv)·hm?2,比CK高126.98%。综合分析温室气体排放、土壤固碳以及秸秆焚烧3个因素,SR1全球升温贡献最低,显著低于NT 4.72%。短期全量秸秆还田有助于降低总体温室气体排放,长期进行秸秆还田后降低幅度会逐步减小。     

CO2 emission in an intensively cultivated loam as affected by long-term application of organic manure and nitrogen fertilizer

A long-term field experiment was conducted to examine the influence of mineral fertilizer and organic manure on the equilibrium dynamics of soil organic C in an intensively cultivated fluvo-aquic soil in the Fengqiu State Key Agro-Ecological Experimental Station (Fengqiu county, Henan province, China) since September 1989. Soil CO₂ flux was measured during the maize and wheat growing seasons in 2002-2003 and 2004 to evaluate the response of soil respiration to additions and/or alterations in mineral fertilizer, organic manure and various environmental factors. The study included seven treatments: organic manure (OM), half-organic manure plus half-fertilizer N (NOM), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer PK (PK) and control (CK). Organic C in soil and the soil heavy fraction (organo-mineral complex) was increased from 4.47 to 8.61 mg C g⁻¹ and from 3.32 to 5.68 mg C g⁻¹, respectively, after the 13 yr application of organic manure. In contrast, organic C and the soil heavy fraction increased in NPK soil to only 5.41 and 4.38 mg C g⁻¹, respectively. In the CK treatment, these parameters actually decreased from the initial C concentrations (4.47 and 3.32 mg C g⁻¹) to 3.77 and 3.11 mg C g⁻¹, respectively. Therefore, organic manure efficiently elevated soil organic C. However, only 66% of the increased soil organic C was combined with clay minerals in the OM treatment. Cumulative soil CO₂ emissions from inter-row soil in the OM and NPK treatments were 228 and 188 g C m⁻² during the 2002 maize growing season, 132 and 123 g C m⁻² during the 2002/2003 wheat growing season, and 401 and 346 g C m⁻² yr⁻¹ in 2002-2003, respectively. However, during the 2004 maize growing season, cumulative soil CO₂ emissions were as high as 617 and 556 g C m⁻², respectively, due to the contribution of rhizosphere respiration. The addition of organic manure contributed to a 16% increase in soil CO₂ emission in 2002-2003 (compared to NPK), where only 27%, 36% and 24% of applied organic C was released as CO₂ during the 2002 and 2004 maize growing seasons and in 2002-2003, respectively. During the 2002/2003 wheat growing season, soil CO₂ flux was significantly affected by soil temperature below 20 °C, but by soil moisture (WFPS) during the 2004 maize growing season at soil temperatures above 18 °C. Optimum soil WFPS for soil CO₂ flux was approximately 70%. When WFPS was below 50%, it no longer had a significant impact on soil CO₂ flux during the 2002 maize growing season. This study indicates the application of organic manure composted with wheat straw may be a preferred strategy for increasing soil organic C and sequestering C in soil.     

长期不同施肥方式对华北地区温室和农田土壤团聚体形成特征的影响

土壤的团聚状况是土壤重要的物理性质之一,团聚体数量是衡量和评价土壤肥力的重要指标。施用有机肥是提高土壤有机碳(SOC)含量、促进土壤团聚体形成和改善土壤结构的重要措施。本文以华北地区曲周长期定位试验站的温室土壤和农田土壤为研究对象,运用湿筛法,对比研究施用化肥(NP)、有机肥加少量化肥(NPM)、单施有机肥(OM)3种施肥方式对温室和农田两种利用方式土壤水稳性团聚体含量、分布和稳定性的影响,以提示施肥措施对不同土地利用方式土壤水稳性团聚体特征的影响。结果表明:在温室土壤和农田土壤中,OM处理较NP和NPM处理显著降低了土壤容重,增加了土壤有机质含量(P0.05),且在0~10 cm土层中效果最为明显。其中在温室土壤0~10 cm土层,单施有机肥处理(OM1)的土壤容重为1.17 g·cm~(-3),分别较施用化肥(NP1)和有机肥加少量化肥(NPM1)处理降低12.0%和8.6%,OM1的土壤有机质含量为54.81 g·kg~(-1),较NP1和NPM1增加104.8%和35.7%;在农田土壤0~10 cm土层,单施有机肥处理(OM2)的土壤容重为1.19 g·cm~(-3),较施用化肥(NP2)、有机肥加少量化肥(NPM2)分别降低8.5%和7.0%,OM2的土壤有机质为22.67 g·kg~(-1),较NP2、NPM2分别增加23.1%和15.0%。温室土壤和农田土壤中,0~10 cm、10~20 cm和20~40 cm层土壤团聚体的平均重量直径(MWD)和几何平均直径(GMD)均为OMNPMNP;OM处理下水稳性团聚体的分形维数(D)值最低,NP处理下最大。OM处理显著降低0~20 cm土层内水稳性团聚体的D值,表层0~10 cm土层效果最为明显,土壤结构明显得到改善;相比农田土壤,温室土壤稳定性指标变化最为明显,团聚体结构改善效果最好。土壤有机质含量与0.25 mm水稳性团聚体含量间呈极显著正相关关系(P0.001),说明土壤有机质含量越高,0.25 mm水稳性团聚体的含量就越高,土壤团聚体水稳性越强,土壤结构越稳定。因此有机施肥方式能在补充土壤有机碳库和有效养分含量的同时,显著增加土壤中大团聚体的含量及其水稳性,是提高华北平原农田土壤、尤其是温室土壤结构稳定性和实现土壤可持续发展的有效措施。     

Application of mixed straw and biochar meets plant demand of carbon dioxide and increases soil carbon storage in sunken solar greenhouse vegetable production

Solar vegetable greenhouse soils show low soil organic carbon content and thus also low rates of soil respiration. Processing vegetable residues to biochar and mixing biochar with maize straw might improve soil respiration and increase soil organic carbon stocks, while preventing the spread of soil-borne diseases carried by vegetable residues. In an incubation experiment, we tested how additions of maize straw (S) and biochar (B) added in varying ratios (100S, 75S25B, 50S50B, 25S75B, 100B and 0S0B (control)) affect soil respiration and fraction of added C remaining in soil. Daily CO₂ emissions were measured over 60 days incubation, the natural abundance of ¹³C in soil and in the added biochar and maize straw were analysed. Our result shows that (a) soil CO₂ emissions were significantly increased compared to soil without the straw additions, while addition of biochar only decreased soil respiration; (b) cumulative CO₂ emissions decreased with increasing ratio of added biochar to maize straw; (c) the abundance of soil ¹³C was significant positively correlated with cumulative CO₂ emissions, and thus with the ratio of straw addition. Our results indicate that incorporation of maize straw in greenhouse soils is a meaningful measure to increase soil respiration and to facilitate greenhouse atmosphere CO₂ limitation while producing vegetables. On the other hand, additions of biochar from vegetable residues will increase soil organic carbon concentration. Therefore, the simultaneous application of maize straw and biochar obtained from vegetable residues is an effective option to maintain essential soil functions for vegetable production in sunken solar greenhouses.     

Carbon budget and seasonal carbon dioxide emission from a central Ohio Luvisol as influenced by wheat residue amendment

Enhancement of soil organic carbon (SOC) stocks through mulching has been proposed, and although this practice can alter several soil properties, its impact on the temporal variability of carbon dioxide (CO₂) emission from soils has not been widely investigated. To that end, we monitored CO₂ fluxes from a central Ohio Luvisol (fine, mixed, mesic Aeric Ochraqualf) amended with wheat (Triticum aestivum L.) straw applied at rates of 0 (M0), 8 (M8) and 16 (M16) Mg dry matter ha⁻¹ per year and supplemented with fertilizer (244 kg N ha⁻¹ per year) or without. The experimental design was a randomized complete block design with three replications. The intensity of CO₂ emission was higher in the late winter (mean: 2.79 g CO₂-C m⁻² per day) and summer seasons (2.45 g CO₂-C m⁻² per day) and lowest in the autumn (1.34 g CO₂-C m⁻² per day). While no significant effect of N fertilization on CO₂ emission was detected, soil mulching had a significant effect on the seasonal variation of CO₂ fluxes. The percentage of annual CO₂ emitted during the winter and spring was similar across treatments (17–22%); however, 43% of the annual CO₂ loss in the M0 plots occurred during the summer as opposed to 26% in the mulch treatments. A close relationship (F=0.47X+4.45, R²=0.97, P<0.001) was found between annual CO₂ flux (F, Mg CO₂-C ha⁻¹) and residue-C input (X, Mg C ha⁻¹). Litter and undecomposed residue amounted to 0.32 and 0.67 Mg C ha⁻¹ per year in the M8 and M16 plots, respectively. After 4 years of straw application, SOC stocks (0–10 cm) were 19.6, 25.6 and 26.5 Mg C ha⁻¹ in the M0, M8 and M16 treatments, respectively. The results show that soil mulching has beneficial effect on SOC sequestration and strongly influence the temporal pattern of CO₂ emission from soils.     

Soil carbon budget in a single-cropping paddy field with rice straw application and water management based on soil redox potential

Abstract

An ideal state for agroecosystems to mitigate global warming should include both decreasing CO₂ and CH₄ emissions and increasing soil carbon storage. Two-year field experiments were carried out to examine the effects of water management (continuous flooding [CF] and Eh control [EH]) and rice straw management (application [+S] and removal [–S]) on the soil carbon budget in a single-cropping paddy field in Japan. The EH water management based on soil redox potential that the authors have proposed decreased the total CH₄ emission during the rice growing period compared with CF. The +S increased CO₂ emission as soil respiration during the non-flooded fallow period compared with –S, but also increased straw residues in the soil. However, there was little evidence for sequential carbon accumulation in the soil over the year by +S. The resultant annual budget of soil carbon was a loss of 32–103 g C m^?2 in the EH+S treatment compared with a loss of 166–188 g C m^?2 in the CF–S treatment. Taking into account the global warming potentials, the EH+S treatment also decreased the total CO₂-equivalent emission compared with the CF–S treatment. Consequently, a combination of appropriate water management and straw application will be an effective option in decreasing both CO₂-equivalent emission and sustaining soil carbon storage.