Effect of biochar on soil structure and storage of soil organic carbon and nitrogen in the aggregate fractions of an Albic soil

ABSTRACT

Field experiment was conducted to evaluate the effect of corn straw derived-biochar (700 °C) applied at 0 (control), 10 (B1), 20 (B2) and 30 t ha^?1 (B3) on water stable aggregate (WSA), mean weight diameter (MWD), total organic carbon (TOC) and total nitrogen (TN) in WSA fractions of Albic soil. Compared with control, WSA in > 2 mm fraction increased, by 40.8% and 51.5% (0–10 cm depth) in B1 and B3, respectively. B1, B2 and B3 (10–20 cm depth) increased by 55.2%, 69.6% and 62.4%, respectively. MWD increased by 34.4%, 21.6%, and 17.6% with B3 at 0–10 cm, 10–20 cm and 20–30 cm depths, respectively. TOC in the > 2 mm fraction increased by 28.6%, 22.1%, and 23.2% (0–10 cm depth) in B1, B2, and B3, respectively, TN in 2–0.5 mm fractions increased by 32.4%, 23.4% and 33.6% (0–10 cm depth); and in the 0.25–0.05 mm fractions increased by 14.8%, 19.8% and 18.7% (10–20 cm depth), in B1, B2 and B3, respectively. Our findings suggest biochar application at 30 t ha^?1 could improve structural stability and sequestration of TOC and TN in Albic soils.     

免耕和秸秆还田对东北黑土区土壤团聚体组成及有机碳 含量的影响

为解决东北黑土区因不合理耕作导致的土壤结构性状变差及有机碳含量下降的问题,该研究于2015年开始,在黑龙江省哈尔滨市东北农业大学向阳试验基地开展。设置免耕+秸秆还田（NTS）、免耕（NT）、翻耕+秸秆还田（CTS）、翻耕（CT）4种处理,于2018、2019年采集土样,研究免耕措施及秸秆还田对东北薄层黑土区0～10、>10～20 cm土壤团聚体稳定性、土壤有机碳含量、各粒径团聚体内有机碳含量的影响。结果表明：2018和2019年0～10、>10～20 cm土层NTS处理>5 mm水稳性团聚体百分比含量及平均重量直径显著高于其他3种处理,NTS及NT处理土壤有机碳含量显著高于CTS及CT处理（P?<0.05）,4种处理各粒径水稳性团聚体有机碳含量峰值总体出现在1～2 mm处,NTS及NT处理>5、2～5、1～2 mm有机碳贡献率整体高于CTS及CT处理。研究表明,免耕与秸秆还田有利于薄层黑土坡耕地耕层土壤团聚体稳定性的提高和各粒级下团聚体有机碳的积累,与其他3种处理相比,免耕+秸秆还田效果更佳。     

Effects of sewage sludge amendment on soil aggregation

Sewage sludge in doses of 200 and 400 Mg ha⁻¹ (dry weight) were applied in an experimental rehabilitation of a limestone quarry to improve soil physical condition. The effect of this organic waste on soil aggregation and structural stability has been tested measuring aggregate size distribution by dry- and wet-sieving procedures over a period of 28 months. We discuss the influence of the organic components of aggregates on soil structure. The main effect of sewage sludge was to increase aggregate stability to raindrop impact (splash) just after application of the former but one year later this effect decreased notably. Organic matter is distributed in different ways between macro- and microaggregates, and this parameter seems to be responsible for the structure changes observed. Copyright © 1999 John Wiley & Sons, Ltd.     

生物炭与氮肥配施改善土壤团聚体结构提高红枣产量

探讨花生壳生物炭配施氮肥对华北平原枣区土壤机械稳定性和水稳性团聚体的分布、稳定性及红枣产量的影响,阐明土壤和枣树对生物炭与氮肥培肥效果的响应,为枣区土壤结构改良和合理培肥制度建立科学依据。通过3 a（2013-2015）田间定位试验,设置生物炭用量4个水平（0,2.5,5和10 t/hm2）、氮肥用量3个水平（300,450和600 kg/hm2）,利用干、湿筛法得到不同粒级的土壤团聚体含量。结果表明：与对照相比,生物炭与氮肥配施对机械稳定性团聚体的平均质量直径（MWD,mean weight diameter）、几何平均直径（geometric mean diameter, GMD）和>0.25 mm大团聚体质量分数无显著影响,但>0.25 mm水稳性大团聚体含量则显著提高20.7%,水稳性团聚体的MWD和GMD较对照分别显著增加29.2%和27.2%。同时,各配施处理降低了土壤团聚体破坏率,最大降幅为27.1%。与对照相比,中、高用量的生物炭与氮肥配施显著提高土壤有机碳含量,且有机碳含量与MWD和GMD均达到了显著水平（P<0.05）。生物炭施入土壤1 a后,随试验时间的推移,与氮肥的培肥效果越来越明显,红枣产量呈上升趋势。综合分析认为,生物炭与氮肥配施对枣区土壤水稳性大团聚体的形成、土壤结构及稳定性提升效果显著,有利于缓解枣区土壤质量退化问题和提高红枣产量。     

改良剂对粘质潮土团聚体特征及分形维数的影响

为评价复合功能改良剂(NSA)对板结土壤的改良效果,通过小白菜盆栽试验,研究NSA对滨州粘质潮土的理化性状、土壤团聚体数量、分布和稳定性的影响。结果表明,增施NSA可降低土壤容重、比重和pH值,提高土壤总孔隙度;施用NSA显著增加了0.5~1mm和0.25~0.5mm的团聚体含量,显著降低了0.05mm的团聚体含量,施用0.5%和1.0%的NSA后,土壤水稳性大团聚体总含量(R0.25)比CK分别显著提高67.14%和141.58%,NSA可将团聚体聚合成更大粒径来实现对土壤结构的改良;添加NSA使平均重量直径(MWD)和几何平均直径(GMD)显著提高,土壤不稳定团粒指数(ELT)显著降低;分形维数(D)随着NSA的添加而减少。施用NSA可促进土壤团聚体的形成,并提高其稳定性,对土壤结构具有显著的改善作用,这对进一步研制多功能的土壤改良剂提供了参考。     

Cropping diversity with rice influences soil aggregate formation and nutrient storage under different tillage systems

Background : The soils under continuous rice monocropping are currently facing a serious threat of accelerated soil and environmental quality degradation. Aims : Examining the impact of tillage and cropping diversity on soil aggregate stability and associated nutrients in a sub‐tropical rice ecosystem. Methods : A split‐plot experiment with tillage (minimum, MT vs. conventional, CT) as a main plot and cropping diversity [mustard (Brassica napus)–rice (Oryza sativa)–rice (M–R–R), wheat (Triticum aestivum)–rice–rice (W–R–R), and lentil (Lens esculenta)–rice–rice (L–R–R)] as a sub‐plot was repeated for four years. Soil aggregate properties were measured using wet sieving techniques. Soil organic carbon (SOC) and nutrients were measured in different aggregate size groups as well as in the bulk soil samples. Results : Results show that all the aggregate size groups were similar in both MT and CT, except in 0.85–0.30 mm. Likewise, cropping diversities increased soil aggregation, being higher aggregate size of < 0.053 mm in M–R–R relative to the W–R–R and L–R–R, where the latter two were alike. By contrast, > 2 mm aggregates were higher in L–R–R than in M–R–R and W–R–R, where the latter two were similar. The MT increased aggregate mean weight diameter (MWD) by 14% in W–R–R, and by 29% in L–R–R. Soil organic carbon (SOC), total N (TN), and available P were higher in MT than in CT, while it was alike for exchangeable K and available S. While W–R–R had a higher aggregate‐associated SOC, available P, and available S, L–R–R had a higher TN, and M–R–R had a higher exchangeable K. While SOC, TN, and exchangeable K accumulated more in the > 0.85 mm size aggregates, the available P, in contrast, accumulated more in < 0.85 mm size aggregates. Conclusion : Wheat–rice–rice diversity, coupled with minimum tillage, has a higher potential for soil fertility sustenance and crop productivity through better nutrient protection.     

长期施用不同有机物料对土壤团聚体特征的影响

农业有机物料是重要的资源,为研究施用不同有机物料对土壤水稳性团聚体分布、稳定性及有机碳的影响,采用对照(CK)、玉米秸秆(Str)、堆肥(C)、牛粪(PM)、沼渣(BgR)、生物炭(BC)6种处理,通过田间7年定位试验,利用湿筛法得到不同粒级的土壤水稳性团聚体,测定土壤有机碳含量,计算了水稳性团聚体平均质量直径(MWD)、几何平均直径(GMD)值、分形维数(D)和土壤不稳定团粒指数(E_(LT))。结果表明:与对照相比,5种不同有机物料处理下0~15 cm土层水稳性大团聚体(0.25 mm)含量、平均质量直径(MWD)、几何平均直径(GMD)、土壤有机碳含量显著增加(P0.05),分形维数(D)、土壤不稳定团粒指数(E_(LT))显著减小(P0.05),土壤团聚体结构稳定性明显得到增强。土壤有机碳与水稳性大团聚体(0.25mm)含量间呈现出极显著正相关关系(P0.001)。生物炭和秸秆处理的团聚体稳定性变化最为明显,土壤结构改善效果最好,生物炭、沼渣处理最有利于促进土壤有机碳的累积。各处理15~30 cm土层,土壤团聚体及有机碳含量差异不显著(P0.05)。采取施用不同有机物料的方式对耕地进行保育,显著提高了耕作层水稳性大团聚体含量和有机碳含量,增强了团聚体结构稳定性,改善了土壤结构和肥力状况。     

不同土地利用方式土壤团聚体组成及几种团聚体稳定性指标的比较

为分析比较不同土地利用方式以及种植年限土壤团聚体质量,获得较灵敏的团聚体状况指标与研究方法,揭示人为活动对土壤质量的作用与影响,以关中地区不同种植年限的菜园土壤和果园土壤为研究对象,经干筛法测定团聚体的组成状况后分别用平均质量直径（MWD）、几何均重直径（GMD）、分形维数D以及矩法参数为指标,分析菜园土壤和果园土壤在系列时间的振动筛分过程中团聚体组成变异特征,结果表明：用MWD和GMD作为团聚状况指标,只有在适宜的振动筛分时间范围内才能基本反映各种性状土壤的团聚水平差异;用分形维数作为指标,表征各类土壤的团聚水平的可信性值得商榷;用矩法的理论和其中的偏倚系数Cs能够较为灵敏地表征各类土壤的团聚水平。同时,研究发现菜园土壤和果园土壤的团聚化水平均有随着种植年限的增加有先提高后降低的趋势。研究得出了矩法的偏倚系数能够更清楚地区分各土壤之间的团聚水平,为评价土壤团聚水平提供更为灵敏的指标。     

玉米茎秆汁液对土壤的减水减沙效益及其机理

为研究土壤改良剂玉米茎秆汁液对中国西部地区水土流失的影响和机理,该文通过室内土壤理化性质测定和人工模拟降雨试验,研究了地表施加玉米茎秆汁液对土壤团聚体的平均重量直径、土壤有机质质量分数和土壤减水减沙效益的影响。试验以未施加任何玉米茎秆汁液的黄土坡面为对照,设计单位面积玉米茎秆汁液施加量1 041.7 mL/m2,施加汁液体积分数25%和50%,降雨强度为50 mm/h,研究玉米茎秆汁液施加对土壤减水减沙的影响。结果表明,玉米茎秆汁液的施加可以增加土壤有机质的含量,提高土壤团聚体的平均重量直径,降低产流产沙速率。对照、体积分数25%和50%汁液施加下的土壤团聚体平均重量直径分别为0.18、0.46和0.51 mm,土壤有机质质量分数分别为5.70%、6.75%和7.17%。较对照,体积分数25%和50%汁液施加下,土壤的减水效益分别为45.81%和48.34%,减沙效益分别为65.00%和75.47%。玉米茎秆汁液的减水减沙效益随时间的推移而降低,月均减水、减沙效益降低量约为1.25%和1.41%,研究中施加体积分数25%和50%汁液的土壤减水减沙效益约可持续3和4.5 a。综上,玉米茎秆汁液作为土壤改良剂在施加量为1 041.7 mL/m2时,茎秆汁液与水的体积比为1:1时,效果较好。该研究可以为将玉米茎秆汁液作为土壤改良剂用于土壤侵蚀的防治提供施放参考。     

湿筛过程中分散液的质量对土壤团聚体稳定性影响

【目的】土壤团聚体是土壤结构的基本单元,决定着土壤在生态系统中的作用和功能。保持良好的结构状态和稳定的结构性能是确保土壤水、 肥、 气、 热肥力因子协调的基本条件。现代土壤管理中大量使用的化肥无机盐以及灌溉水体富含的离子都会造成对团聚体的破坏,本文以富含有机质的黑土为研究对象,探索湿筛过程中分散溶液的质量对团聚体稳定性的影响。【方法】以氯化钠、 氯化钙和氯化铝3种不同价态的阳离子溶液为介质,采用改进的萨维若夫（Саввинов）法进行湿筛,设置0（不加盐去离子水,CK）、 0.1、 0.3、 0.5 mol/L 4个浓度水平,研究直径0.25 mm的土壤团聚体在不同阳离子盐溶液作用下的稳定性。【结果】不同盐溶液中黑土团聚体的稳定性差异很大。在氯化钠盐溶液中,黑土团聚体的盐破坏率（PAD0.25/w）均为正值,且随钠盐溶液浓度的增大而增加,在浓度为0.1、 0.3和0.5 mol/L的氯化钠溶液中分别为0.21%、 10.7%和14.4%。在氯化钙溶液和氯化铝溶液中,黑土PAD0.25/w均为负值, 氯化钙溶液中PAD0.25/w的绝对值随着盐浓度的增大而减小,氯化铝溶液中PAD0.25/w的绝对值均在51%以上。【结论】一价盐溶液加剧了0.251 mm黑土团聚体的分散,但能够保护直径1 mm以上的团聚体,而二价盐和三价盐溶液对团聚体的分散有明显的抑制和保护作用。     

New wings on the interaction between conventional subsoiler and paraplow tines with the soil: effects on the draft and the properties of soil

Equipping tines with the wings increases draft and soil loosening. Wing angles affect tine performance, soil aggregation and remained residue. In this research, conventional wing with no bent plus backward and forward bent wings with bend angles of 10 and 20° were attached to both a subsoiler and paraplow tine. The rake angle of all wings was 15°. The effects of tine and wing on draft, soil disturbance area, specific draft, remained residue, and mean weight diameter (MWD) were investigated in a clay loam soil at depth of 40 cm and speed of 1.6 km h^?1. The effect of tine and wing plus interaction of them on all parameters was significant (p < 0.01) with the exception of remained residue. The bent-winged tines required higher draft and caused higher disturbance area, lower specific draft, and lower MWD than the conventional tines and those without wing. The highest draft, disturbed area and remained residue plus the lowest specific draft and MWD were obtained when applying the 10° forward bent-winged tines. In present work, the paraplow equipped with forward bent wings with a bend angle of 10° was suggested as a suitable tool for deep soil loosening under a conservation tillage system.     

长期日光温室试验条件下不同施肥处理对土壤团聚体稳定性和铁铝氧化物含量的影响

Soil in greenhouses is likely to suffer a gradual decline in aggregate stability. Determination of the effects of different fertiliser practices on soil aggregate stability is important for taking advantage of solar greenhouses. Soil aggregate stability and iron(Fe) and aluminium(Al) oxide contents were investigated in a 26-year long-term fertilisation experiment in greenhouse in Shenyang, China,under eight fertiliser treatments: manure(M), fertiliser N(FN), fertiliser N with manure(MN), fertiliser P(FP), fertiliser P with manure(MP), fertiliser NP(FNP), fertiliser NP with manure(MNP), and control without any fertiliser(CK). A wet sieving method was used to determine aggregate size distribution and water-stable aggregates(WSA), mean weight diameter and geometric mean diameter as the indices of soil aggregate stability. Different fertiliser treatments had a statistically significant influence on aggregate stability and Fe and Al oxide contents. Long-term application of inorganic fertilisers had no obvious effects on the mass proportion of aggregates. By contrast, manure application significantly increased the mass proportion of macroaggregates at the expense of microaggregates. All treatments, with the exception of FNP, significantly increased the stability of macroaggregates but decreased that of microaggregates when compared with CK. Aggregation under MP and MN was better than that under M and MNP; however,no significant differences were found among inorganic fertiliser treatments(i.e., FN, FP, and FNP). A positive relation was found between pyrophosphate-extractable Fe and WSA(r = 0.269), but no significant relations were observed between other Fe and Al oxides and aggregate stability.     

子午岭植被恢复过程中土壤团聚体有机碳含量的变化

土壤有机碳是土壤团聚体形成的重要胶结剂之一，土壤团聚体分布影响有机碳含量及其稳定性。对子午岭植被恢复过程中团聚体有机碳含量变化的研究结果显示：相对于农田，植被恢复可增加土壤各个粒径团聚体有机碳含量．同时增加不同层次土壤团聚体有机碳含量。就粒径而言，虽然各个植被下〈0．25mm土壤团聚体有机碳含量最低，植被类型变化对土壤团聚体有机碳含量影响最大的是〈0．25mm粒径，辽东栎林地〈0．25mm土壤团聚体有机碳含量是农田〈0．25mm团聚体有机碳含量的3倍；其次，植被类型对〉5mm团聚体有机碳含量影响较大，辽东栎、早期森林、灌丛、草地和弃耕地土壤〉5mm团聚体有机碳含量比农田土壤〉5ram团聚体有机碳含量高149％，209％，104％，62％，10％。说明植被演替可增加土壤团聚体有机碳含量，但首先是增加较大粒径团聚体的有机碳含量；随着植被的进一步演替，小粒径团聚体有机碳含量也相应的增加，这部分有机碳是稳定的，说明植被恢复增强了土壤的碳汇功能。     

黄土高原丘陵沟壑区土地利用方式对土壤团聚体特征的影响

为研究黄土高原丘陵沟壑区复垦土地在不同利用方式下对土壤团聚体的影响,以陕西延安南泥湾沟壑区退化耕地整治复垦后,5种不同的土地利用方式,分别为林地(F处理),水稻(R处理),玉米(M处理)、蔬菜(V处理)及荒地(CK处理)。测定分析干筛法和湿筛法0—40cm土层土壤0.25mm团聚体分布、平均重量直径(MWD)、几何平均直径(GMD)、团聚体破坏率(PAD)和分形维数(D)。结果表明:(1)各处理在0—40cm各土层土壤团聚体数量及大小均显著优于CK处理,各处理干筛下0—40cm土层0.25mm团聚体含量(DR0.25)和湿筛下该团聚体含量(WR0.25)随着土壤土层深度的增加呈现相反的趋势;(2)干筛法和湿筛法0—40cm土层各处理土壤平均重量直径(MWD)和几何平均直径(GMD)的平均值大小顺序均呈现F处理R处理M处理V处理CK处理,F处理和R处理对增加土壤团聚体较其它处理效果显著;(3)湿筛法分析表明,各处理土壤团聚体破坏率(PAD)在0—40cm土层内均表现出近似Z字形趋势,各处理显著低于CK;(4)各处理的分形维数(D)在0—40cm土层平均值大小顺序为F处理R处理M处理V处理CK处理。土壤分形维数(D)与干筛法和湿筛法下0—40cm土层0.25mm团聚体含量之间存在良好的线性关系,分别为R2=0.73和R2=0.80。林地和水稻田利用方式可有效提高土壤团聚体数量和质量,增加土壤稳定性和改善土壤结构。     

长期有机无机肥配施对土壤水稳性团聚体酶活性的影响

The activities of invertase, protease, urease, acid phosphomonoesterase, dehydrogenase, and catalase in different fractions of waterstable aggregates (WSA) were examined in long-term (26 years) fertilised soils. The long-term application of organic manure (OM) with chemical fertiliser (CF) significantly increased macroaggregate and decreased microaggregate percentages, enhanced the mean weight diameter, and significantly increased soil total carbon (TC) and total nitrogen (TN) contents of WSA in different size fractions. Combined fertilisation with OM and CF also increased invertase, protease, urease, acid phosphomonoesterase, dehydrogenase, and catalase activities of WSA in different size fractions. Enzyme activities were higher in macroaggregates than in microaggregates. The distribution of enzyme activities generally followed the distribution of TC and TN in WSA. The geometric mean of the enzyme activities in different WSA of OM-treated soils was significantly higher than that in soils treated with 100% CF or no fertiliser. The results indicated that the long-term combined application of OM with CF increased the aggregate stability and enzyme activity of different WSA sizes, and consequently, improved soil physical structure and increased soil microbial activity.     

Effects of combined organic manure and mineral fertilization on soil aggregation and aggregate-associated organic carbon in two agricultural soils

Abstract

The effect of organic manure and inorganic fertilizer on soil aggregate size distribution and stability, and associated carbon (C) within aggregates varies greatly in previous studies because of the differences in soil conditions, cropping systems, and management practices. This study was conducted as two field fertilization experiments, with different cropping systems, under a subtropical climate in China. The two field experiment sites were located in Jinhua (established in April 2011) in the Jinqu basin in Zhejiang province and Jintan (established in October 2010) in the low-middle Yangtze River plain in Jiangsu province. Both experiments consisted of four treatments, including unfertilized (CK), mineral fertilizer nitrogen (N)–phosphorus (P)–potassium (K) (NPK), NPK plus straw (NPK?+?SR), and NPK plus cattle manure (NPK?+?FYM) or half NPK plus cattle manure (1/2NPK?+?FYM). Water stable aggregate size classes (>5, 2–5, 1–2, 0.5–1, 0.25–0.5, and <0.25?mm) and associated soil organic C (SOC) at 0–15?cm depth were measured. The mean weight diameter (MWD), geometric mean diameter (GMD), and water stable aggregates (WSA)?>?0.25?mm were also determined. The results showed that aggregate-size distribution varied with soil types. Combined application of NPK and organic matter (straw residue or cattle manure), unlike the CK and NPK treatments, significantly increased the WSA >0.25?mm, MWD, and GMD, while obviously reducing the proportion of <0.25?mm aggregates. However, no differences in WSA >0.25?mm, MWD, GMD, and associated C were observed between CK and NPK at both sites. The addition of FYM to the NPK treatment yielded the highest SOC contents in bulk soil, and showed significantly higher associations of C within all size aggregates at both sites. In contrast, NPK?+?SR significantly increased SOC within aggregate classes (2–5?mm, 0.5–1?mm, 0.25–0.5?mm, and <0.25?mm) at Jinhua and (>5?mm and 1–2?mm) at Jintan compared to the CK and NPK treatments. Overall, the combined application of FYM and mineral NPK was the best sustainable management practice for the improvement of aggregate stability and SOC sequestration.     

Effects of phenolic acids on seed germination and seedling growth in soil

Summary It is commonly assumed that the adverse effect of plant residues on crop yields is largely or partly due to phytotoxic compounds leached from these residues or produced by their decomposition. There has been substantial support for the hypothesis that the phytotoxic compounds responsible for reduced crop yields are phenolic acids such as p-coumaric acid, p-hydroxybenzoic acid, and ferulic acid. To test the validity of this hypothesis, we studied the effects of nine phenolic acids (caffeic acid, chlorogenic acid, p-coumaric acid, ellagic acid, ferulic acid, gallic acid, p-hydroxybenzoic acid, syringic acid, and vanillic acid) on (1) seed germination of corn (Zea mays L.), barley (Hordeum vulgare L.), oats (Avena sativa L.), rye (Secale cereale L.), sorghum [Sorghum bicolor (L.) Moench], wheat (Triticum aestivum L.), and alfalfa (Medicago sativa L.) on germination paper and soil, (2) seedling growth of alfalfa, oats, sorghum, and wheat on germination paper and soil, and (3) early plant growth of corn, barley, oats, rye, sorghum, and wheat in soil. The results showed that although the phenolic acids tested affected germination and seedling growth on germination paper, they had no effect on seed germination, seedling growth, or early plant growth in soil even when the amounts applied were much greater than the amounts detected in soil. We conclude that the adverse effect of plant residues on crop yields is not due to phenolic acids derived from these residues.     

秸秆不同处理方式对黄绵土团聚体特性的影响

以采自中国科学院安塞水土保持综合试验站基地的粉砂质黄绵土壤为试验用土,研究秸秆不同处理方式对黄绵土结构的影响。结果表明,(1)粉碎秸秆与硫酸钙配施处理能显著增加黄绵土水稳性团聚体,各评价指标与对照组(裸土)差异显著(P0.05),同时该处理降低了土壤结构的分形维数,有效提高土壤结构稳定性;(2)粉碎氨化秸秆以及与硫酸钙改良剂混合施用对提高黄绵土水稳性团聚体含量有一定的迟效性;(3)在整个培养期内,长秸秆改良土壤结构作用缓慢,单施硫酸钙对黄绵土结构无明显改良作用,土壤结构分形维数与团聚体评价指标大于0.25的土壤团聚体结构含量(R0.25)、平均质量直径(WMD)、平均几何直径(GMD)各值均呈极显著负相关关系(P0.01)。总之,不同处理方式的秸秆施入土壤后,对原状土的扰动方式不尽相同;采用团聚体分形维数可定量描述土壤结构的动态演变过程。     

Soil aggregate stability and aggregate-associated organic carbon under different land use or land cover types

Soil aggregate stability (SAS) is an indicator for soil condition and is greatly influenced by land use or land cover (LULC) type and other soil and environmental attributes. This study investigated the soil aggregate-size distribution, SAS, aggregate-associated organic carbon (AAOC) and the relative importance of factors affecting SAS and AAOC. Based on conditioned Latin hypercube sampling, soil aggregate samples were collected from the “A” horizon and wet sieved into large macroaggregates (>2.0 mm), small macroaggregates (0.25–2.0 mm), microaggregates (0.053–0.25 mm) and mineral fraction (<0.053 mm). The large macroaggregates accounted for 86% to 93% of the total aggregates under all LULC types except under dry land (64%) and paddy land (35%). The SAS under different LULC decreased in the order fir > shrubland > natural grassland > orchard > blue pine > broadleaf > mixed conifer > dry land > paddy land. The AAOC of the large macroaggregates constituted for 76%–90% of the total AAOC under all LULC types except under dry land (65%) and paddy land (38%). While SAS was largely influenced by the AAOC of small macroaggregates, microaggregates and large macroaggregates and LULC type, the AAOC of different aggregate fractions was mostly affected by LULC type, altitude and slope. SAS did not exhibit any significant relationship with the AAOC of different aggregate fractions under the natural LULC types but showed a strong relationship under the agricultural land indicating that AAOC is more critical for SAS under the agricultural land than under the natural LULC.     

不同耕作和种植模式对土壤团聚体分布及稳定性的影响

通过多年定位试验,研究黄土高原丘陵沟壑区不同耕作制度和种植方式对坡耕地土壤团聚数量、分布和稳定性的影响。结果表明,不同耕作方式下,免耕覆盖处理和免耕处理可明显增加土壤中大团聚体的含量,免耕覆盖处理有着相对更高的团聚体稳定性,并且更易形成5mm水稳性团聚体;不同种植方式下,处理对大团聚体含量影响差异不显著。在同一耕作方式下不同种植方式的土壤大团聚体含量变化趋势不同。相关分析表明,大团聚体含量为土壤团聚体平均重量直径(MWD)产生影响的主要因素,容重对土壤团聚体平均重量直径亦有影响,团聚体破坏率只对水稳团聚体平均重量直径有影响。