黄土区几种土壤培养过程中可溶性有机氮的变化及其与土壤矿化氮的关系

研究了黄土高原12种土壤(农地和林地)35 d好气培养过程中可溶性有机氮(SON)含量及其占可溶性全氮(TSN)的比例,以及SON与土壤矿化氮间的关系。结果表明,随着培养过程的进行,不同类型土壤SON的含量均呈明显增加;土壤SON占TSN的比例在培养的前3 d内明显下降,随后这一比例基本保持在24%左右。根据总可溶性氮确定的供试土壤氮素矿化势No平均为45.8 mg/kg,较由矿化的无机氮确定的土壤氮素矿化势No(平均36.5 mg/kg)高约1/4左右;培养过程中土壤SON含量与利用无机氮拟合得到的土壤氮素矿化势No间的相关性未达显著水平。研究表明,评价土壤氮素矿化特性时仅仅测定矿化的无机氮数量,可能会低估土壤氮素矿化潜力和氮素损失的数量和效应。     

对间隙淋洗长期通气培养条件下黄土高原土壤供氮能力的评价

采用间隙淋洗长期通气培养法,通过对黄土高原物理化学性质差异较大的10种农田土样起始矿质氮、起始提取态总氮、起始可溶性有机氮,以及培养期间淋洗矿质氮、淋洗总氮、可溶性有机氮含量及其与作物吸氮量关系的研究,分析并评价黄土高原主要农田土壤氮素矿化能力以及包括和不包括培养淋洗可溶性有机氮对土壤供氮能力的影响。结果表明,供试土样起始可溶性有机氮平均为N 23.9 mg/kg,是起始提取态总氮的28.8%,土壤全氮的2.4%。在通气培养淋洗总氮中,可溶性有机氮所占比例不高,经过217 d通气培养,淋洗出的可溶性有机氮平均为N 28.8mg/kg,占淋洗总氮量的19.8%。相关分析表明,淋洗可溶性有机氮量与第1季作物吸氮量相关不显著,但与连续2季作物总吸氮量显著相关。淋洗矿质氮、淋洗总氮与两季作物总吸氮量的相关系数明显高于与第一季作物吸氮量的相关系数;与第一季作物吸氮量达显著相关水平,与连续两季作物吸氮量达极显著相关水平。总体上看,可溶性有机氮和土壤全氮、土壤微生物氮不能作为反映短期可矿化氮的指标;间隙淋洗通气培养淋洗液中淋洗矿质氮、淋洗总氮是评价可矿化氮的较好指标,不仅适宜于第一季作物,而且也适用于对连续两季作物土壤供氮能力的评价。     

Nitrogen Mineralization in Soils Related to Initial Extractable Organic Nitrogen: Effect of Temperature and Time

An important source of nitrogen (N) for crops is mineralization of soil organic matter during the growing season. Awareness is growing that dissolved organic nitrogen (DON) plays an important role in mineralization and plant uptake. We studied the influence of temperature and time on extractable organic nitrogen (EON) levels, which is a measure of DON, and their relationship with N mineralization. Aerobic incubation experiments were conducted in the laboratory for five soils at different temperatures (4 20, and 30 °C) and different time intervals with optimal water content (60% of its water-holding capacity). Net N mineralization ranged between 14 and 155 mg kg^–1 within 84 days and was correlated with the initial amount of EON. Net N mineralization among the soils, time, and incubation temperatures was linearly related to the square root of time multiplied by temperature, with mineralization rate k being independent of time and temperature. Because initial EON values were also related to these kvalues, we were able to describe the net N mineralization at different temperatures based on an analysis of initial EON. Preliminary validation with results from pot experiments in the literature suggests that the approach is promising, although the proposed model needs to be calibrated with more soils.     

黄土高原典型土壤有机氮矿化过程中非交换性铵态氮的变化

以黄土高原从北向南不同地区典型土壤类为对象，采用Bramner淹水培养法，研究黄土高原不同生境条件下土壤有机氮矿化过程中非交换性铵态氮的变化。结果表明：土壤非交换性NH4^＋ -N随Bremner法淹水培养时间延长，含量增加。不同土壤类型在培养20d时非交换性NH4^＋ -N的增加量存在显著差异（p=0．0229），而培养40d和60d时差异不显著（P分别为0．1379和0．1159）。培养期间非交换性NH4^＋ -N的增加量均表现为以土垫旱耕人为土最大，其次是黄土正常新成土，简育干润均腐土和干湿砂质新成土较小；添加有机物料极显著影响培养期间的非交换性NH4^＋ -N增加量（培养20d、40d和60d时P分别为0．0002，0．004和0．0003），表现为紫花苜蓿和长芒草土壤非交换性NH4^＋ -N的增加量均极显著高于不添加有机物料的对照土壤；在培养20d、40d和60d时，加（NH4）2SO4土样非交换性NH4^＋ -N的增加量显著大于不加（NH4）2SO4土样（户分别为0．0037，0．0033和0．0027），这是土壤对（NH4）2SO4中NH4^＋ -N固定的必然结果；不同植被类型土壤培养20d时的非交换性NH4^＋ -N增加量差异显著（P=0．0434），培养40d和60d时差异不显著（p分别为0．7378和0．5375）；长期秸秆和氮肥配施土壤非交换性NH4^＋ -N增加量大于不施肥对照土壤，但差异不显著土壤黏粒、全氮和有机质与培养0d、20d、40d和60d时土壤的非交换性NH4^＋ -N含量均呈极显著正相关；而非交换性NH4^＋ -N的增加量与粘粒无相关性，但与全氛和有机质呈显著正相关。     

Comparative Study on Disturbed and Undisturbed Soil Sample Incubation for Estimating Soil Nitrogen-Supplying Capacity

Application of nitrogen (N) fertilizers without knowing the N-supplying capacity of soils may lead to low N use efficiency, uneconomical crop production, and pollution of the environment. Based on the results from pot experiments treated with soil initial nitrate leaching and native soil, long-term alternate leaching aerobic incubation was conducted to study the disturbed and undisturbed soil N-supplying capacity of surface soil samples in 11 sites with different fertilities on the Loess Plateau. The results indicated that the entire indexes and ryegrass (Lolium perenne) uptake N with soil initial nitrate leaching showed a better correlation than that without soil initial nitrate leaching. Except the correlation coefficients for soil initial nitrate (NO₃ ^?)-N and mineral N extracted by calcium chloride (CaCl₂) before aerobic incubation with ryegrass uptake without soil initial nitrate leaching, the correlation coefficients for soil initial NO₃ ^?-N and mineral N extracted by CaCl₂ before aerobic incubation with ryegrass uptake with soil initial nitrate leaching and those for mineralizable N extracted by aerobic incubation, soil initial mineral N and mineralizable N extracted by aerobic incubation, potentially mineralizable N (N₀) and soil initial mineral N + N₀ with ryegrass uptake N under the two cases in disturbed treatment were all higher than those in undisturbed treatment. We concluded that NO₃ ^?-N in soil extracted by CaCl₂ before aerobic incubation can reflect soil N-supplying capacity but cannot reflect soil potential N-supplying capacity. Without soil initial nitrate leaching, the effect of disturbed and undisturbed soil samples incubated under laboratory conditions for estimating soil N-supplying capacity was not good; however, with soil initial nitrate leaching, this method could give better results for soil N-supplying capacity. Based on the results from pot experiments treated with soil initial nitrate leaching and native soil, the mineralization of disturbed soil samples can give provide better results for predicting soil N-supplying capacity for in situ structure soil conditions on the Loess Plateau than undisturbed soil samples.     

Nitrogen Mineralization Characteristics of Disturbed and Undisturbed Soil Samples for Four Main Soil Types on the Loess Plateau

Long-term alternate leaching aerobic incubation was conducted to study nitrogen (N) mineralization in four main soil types under disturbed (D) and undisturbed (UD) conditions from the Loess Plateau (China). Results showed that N mineralization of the UD and D samples decreased from southern to northern Shaanxi Province. Nitrate was the main component of N mineralization during the aerobic incubation for both the D and UD samples. However, net inorganic N in the D samples was less than in UD samples. The average total mineralized N levels were 30% larger for the set of D samples than for the UD samples, and the mineralization potential of the D samples was larger than that of UD samples. Further studies are required to develop predictive methods for quantifying N availability.     

黄绵土不同形态有机氮径流流失规律

利用不同坡度径流小区,在自然降水条件下,研究侵蚀泥沙不同形态有机氮的流失规律,结果表明：在4次产流泥沙中,除氨基糖氮含量减少外,其它有机形态氮均存在增加趋势,以氨态氮含量增加最为显著。随坡度的下降,水解全氮、氨态氮和氨基酸氮含量呈增加趋势;泥沙中水解全氮、氨基酸氮、氨态氮、非酸水解氮均存在不同程度的富集,其富集率随坡度的下降而增大,以氨基酸氮富集程度高,泥沙中氨基糖态氮反而无富集现象存在;当坡度分别为25°、20°、15°、10°和5°时,水解全氮流失量分别为1135.0、763.7、485.5、313.0 和154.4 kg/km²,而氨基酸氮流失量则为234.8、182.7 、121.1、76.8和33.9 kg/km²,占水解全氮的20.6%～24.9%。氨态氮流失量为742.5、503.3 、322.2、208.9、97.4 kg/km²,占水解全氮的63.1%～66.7%。氨基糖氮占酸水解氮1.1%～2.9%。非鉴别氮占水解全氮的5.8%～12.6%。而酸水解氮与非酸水解氮之比分别为1.5、1.5、1.4、1.8和2.3。     

Comparison of Chemical Methods of Assessing Potentially Available Organic Nitrogen from Organic Residues Applied to a Sandy Soil

Abstract

More than 90% of the nitrogen (N) in soils is bond as organic N compounds. The available N can be estimated on the mineral N released during time‐consuming incubations of soil. Several chemical methods have been developed as substitutes for incubations. On the other hand, there has been an increase in waste production. Residues could potentially offset the need for mineral fertilizers, being both an economic and environmental benefit. Thus, the development of a routine method for prediction of N supply both from soil organic matter (SOM) and the application of organic residues is of great interest. An incubation experiment was performed in a Cambic Arenosol to evaluate different chemical methods. Air‐dried soil was mixed with increasing amounts of composted solid municipal waste, secondary pulp‐mill sludge, hornmeal, poultry manure, the solid phase from pig slurry, and composted pig manure. Samples were incubated for 244 days under a controlled environment. Among the chemical extractants studied, hot 2 M potassium chloride (KCl) and hot 0.01 M calcium chloride (CaCl₂) showed promise in indicating values of N₀ (potentially available nitrogen), and these simple methods are suitable for use in routine laboratory conditions.     

黄土高原南北主要类型土壤氮组分相关关系研究

黄土高原作为典型生态脆弱区,不同植被覆盖下土壤氮组分分布特征及相关关系研究一直受到学术界的广泛关注。本研究采集从北向南依次分布的干润砂质新成土(神木)、黄土正常新成土(延安)和土垫旱耕人为土(杨凌)等典型土壤剖面0~200 cm土层土样,分析了土壤全氮及酸解有机氮含量、酸解有机氮主要组分与微生物生物量氮之间的相关性,以期阐明黄土高原典型土壤主要氮组分之间的相关性及其特点。结果表明:黄土高原从北到南典型土壤全氮与微生物生物量氮、固定态铵及酸解有机氮各组分含量之间的相关性均达到极显著水平(P0.01),微生物生物量氮除了与固定态铵及酸解氨基糖态氮没有显著相关性外,与其余氮组分均达到极显著线性相关水平(P0.01),且酸解氨基酸态氮是微生物生物量氮的主要贡献者。     

秸秆和生物质炭添加对陇中黄土高原旱作农田土壤氮素矿化的影响

通过采集2014年设置于甘肃省定西市李家堡镇的不同碳源配施氮素田间定位试验土壤进行120天的室内培养试验,利用Stanford间歇淋洗培养法研究了无碳素和氮素添加(N0)、只施氮素(N100)、秸秆配施氮素(SN100)和生物质炭配施氮素(BN100)4种施肥方式对陇中黄土高原旱作农田土壤氮素矿化的影响.结果表明:秸秆...     

降水条件下黄土坡地氮素淋溶特征的研究

坡地氮素淋溶是导致坡地土壤质量退化和农业非点源污染的重要原因之一。为了深入理解坡地氮素淋溶特征,采用了人工模拟降雨和天然降雨观测方法,对黄土坡地氮素淋溶特征进行了试验研究。结果表明:从坡底到坡顶土壤NO3--N含量呈不断衰减的波浪形状变化,坡底有明显NO3--N累积,其累积含量占全坡面37%~52%;坡地土壤NO3--N淋溶是二维迁移,即随着入渗水既向土体深层迁移,又向坡底迁移;降雨量分别与NO3--N淋溶深度和淋失量均呈正相关,大约每4 mm降雨量可使NO3--N下渗1 cm。本研究为建立坡地养分运移模拟模型提供了初步设想。     

不同有机替代对黄土旱塬土壤碳、氮组分及冬小麦产量的影响

探讨黄土旱塬冬小麦区不同有机肥替代化肥氮对小麦产量及土壤碳氮组分的影响,为该区减施化学氮肥、促进小麦提质增效和农业绿色可持续发展提供理论依据。于2019年在山西黄土旱塬冬小麦种植区设置100%化肥N处理(HF)、10%腐殖酸N+90%化肥N (F1)、30%腐殖酸N+70%化肥N (F3)、50%腐殖酸N+50%化肥N (F5)、10%有机肥N+90%化肥N (Y1)、30%有机肥N+70%化肥N (Y3)、50%有机肥N+50%化肥N (Y5)7个试验处理,系统研究了不同比例腐殖酸、有机肥替代化肥对小麦产量及产量构成和土壤碳、氮组分含量的影响。结果表明:F3、F5、Y3和Y5处理,分别较HF显著提高9.7%,8.0%,9.2%和18.2%。同时,Y5对土壤中各种活性有机碳、氮组分含量的提高均有显著促进作用,提高幅度在36.8%~114.4%和27.8%~105.4%;Y3处理下可溶性、水溶性、微生物有机碳、氮和轻组有机碳、氮组分的含量较HF显著提高21.1%~156.8%;F3和F5处理下土壤中可溶性、微生物和轻组有机碳、氮组分含量较HF显著提高25.4%~119.3%。可溶性有机碳、微生物有机氮、轻组有机氮与籽粒产量呈极显著正相关;可溶性有机氮通过促进公顷穗数增加而提高冬小麦产量;总有机碳、水溶性有机碳和微生物有机氮则通过提高穗粒数达到增产效果。综上,在黄土旱塬冬小麦种植区进行30%~50%的有机肥和腐殖酸替代化肥后,可达到显著增产效果,同时提高土壤中活性碳、氮组分的作用。其中,50%有机肥替代处理的增产与培肥地力效果更为显著,适宜在当地推广应用。     

黄土塬区春玉米氮肥-水分-产量关系研究

土壤水分是制约我国西北干旱半干旱地区农业发展的重要因素,探寻科学合理的氮肥—水分—产量关系,对于促进区域农业持续发展有重要的理论与实践意义。在陕西省长武县的中国科学院长武黄土高原农业生态试验站进行氮肥递减试验,在传统施氮250 kg/hm~2(N6)的基础上,依次递减20%,设置CK、N1、N2、N3、N4、N5、N6 7个处理。结果表明:(1)春玉米生育期土壤耗水量随氮肥施用量的增加而增加,土壤水分亏缺主要发生在80 cm以下土层,且水分亏缺程度随施氮量增加而加重。(2)春玉米产量和水分利用率均随氮肥用量的增加呈现二次抛物线趋势变化。春玉米传统施氮量(N6,250 kg/hm~2)已严重过量,减氮20%(N5,施氮量200 kg/hm~2)可以取得较高的产量和水分利用率。2年N5籽粒产量较N6分别增加9.6%和5.8%,水分利用率提高14.5%和9.1%。因此,建议把减氮20%(N5,即200 kg/hm~2施氮量)作为试验区推荐施氮量。     

黄土高原地区土壤有机碳估算及其分布规律分析

黄土高原地区开展退耕还林还草,不仅会改变生态环境,也势必培育土壤,影响全球碳循环。要准确预测退耕还林对黄土高原乃至全球未来环境的影响作用,需要估算目前黄土高原地区土壤有机碳量。根据第二次土壤普查资料和土壤类型图,计算了黄土高原地区表层土壤有机碳密度和储量。结果表明,黄土高原地区0～20cm土壤有机碳密度变幅为0.66～12.18kgC/m2,其中大部分土壤有机碳密度集中在1～4kgC/m2,土壤有机碳面积平均加权值为2.49kgC/m2,总储量为1068Tg。此结果可为水土保持的环境效益评价提供背景资料,以便通过对比分析退耕还林前后的土壤碳密度,预测未来区域生态环境状况。     

Kinetic Parameters of Gross N Mineralization of Peat Soils as Related to the Composition of Soil Organic Matter

Peat land has been considered as an alternative type of land for agricultural development especially in the tropics. In the present study, the N-supplying capacity, one of the most important soil properties in terms of crop production, of peat soils was examined. Ten peat soil samples were collected from Indonesia, Malaysia, and Japan. Gross N mineralization in the soil samples was estimated using a zero-order model, and kinetic parameters of mineralization were determined using a simple type model. Soil organic matter composition was investigated using ¹³C CPMAS NMR. Mineralization potential ( N ₀), apparent activation energy ( E _a), and mineralization rate constant ( k ) ranged between 571–2,445 mg kg⁻¹, 281–8,181 J mol⁻¹, and 0.009–0.020 d⁻¹, respectively. Although none of the parameters showed a significant correlation with the soil C/N ratio, a negative correlation was observed between the k value and the ratio of the proportion of alkyl C in total C to that of O -alkyl C estimated by ¹³C CPMAS NMR. The latter suggested that the k values were higher in the peat soils relatively rich in readily decomposable organic matter including carbohydrates.     

灌溉方法对保护地土壤有机氮组分及剖面分布的影响

用Bremner有机氮分组法测定了连续7年采用不同灌溉方法灌溉的保护地土壤各剖面层次有机氮组分含量。结果表明,土壤全氮及有机氮各组分含量均随土层深度的增加而降低,但有机氮各组分占全氮的比例随土层深度增加的变化却无明显规律。用3种灌溉方法灌溉,不同土层间土壤有机氮各组分含量的差异主要存在于0~50 cm土层,50 cm以下差异很小;相同土层,土壤有机态氮含量均以酸解氮为主,且酸解氮中各组分绝对含量和相对含量的大小排列顺序均为,未知态氮>氨态氮>氨基酸态氮>氨基糖态氮。在0~80 cm土层,土壤酸解氮占全氮的比例大多在58%~60%之间,只有渗灌处理0~10 cm,10~20 cm及沟灌处理0~10 cm土层酸解氮占全氮的比例较低,分别为34.21%,50.75%和48.02%;而非酸解氮占全氮的比例大多在32%~36%之间。3种灌溉方法相比较,除个别层次外,酸解氮中氨基酸态氮、氨基糖态氮及氨态氮占全氮的比例在各土层中滴灌和渗灌处理均高于沟灌处理,而酸解未知态氮和非酸解氮占全氮的比例则为沟灌处理高于滴灌和渗灌处理。     

灌溉方法对保护地土壤有机氮组分及剖面分布的影响

用Bremner有机氮分组法测定了连续7年采用不同灌溉方法灌溉的保护地土壤各剖面层次有机氮组分含量。结果表明,土壤全氮及有机氮各组分含量均随土层深度的增加而降低,但有机氮各组分占全氮的比例随土层深度增加的变化却无明显规律。用3种灌溉方法灌溉,不同土层间土壤有机氮各组分含量的差异主要存在于0～50 cm土层,50 cm以下差异很小;相同土层,土壤有机态氮含量均以酸解氮为主,且酸解氮中各组分绝对含量和相对含量的大小排列顺序均为,未知态氮〉氨态氮〉氨基酸态氮〉氨基糖态氮。在0～80 cm土层,土壤酸解氮占全氮的比例大多在58%～60%之间,只有渗灌处理0～10 cm,10～20 cm及沟灌处理0～10 cm土层酸解氮占全氮的比例较低,分别为34.21%,50.75%和48.02%;而非酸解氮占全氮的比例大多在32%～36%之间。3种灌溉方法相比较,除个别层次外,酸解氮中氨基酸态氮、氨基糖态氮及氨态氮占全氮的比例在各土层中滴灌和渗灌处理均高于沟灌处理,而酸解未知态氮和非酸解氮占全氮的比例则为沟灌处理高于滴灌和渗灌处理。     

不同有机物料对黄土高原治沟造地土壤水分运移的影响

为了改善黄土高原治沟造地土壤结构较差的问题,采用一维定水头土柱模拟试验,探讨了不同有机物料(生物有机肥、粉碎秸秆、50%粉碎秸秆+50%生物有机肥、尿素、对照)对治沟造地土壤湿润锋推移、累积入渗量、入渗速率和土壤水分蒸发特征的影响,并采用Green-Ampt模型、Philip模型和Kostiakov模型拟合分析土壤水分入渗规律。结果表明:(1)粉碎秸秆与有机肥均降低了土壤水分移动速率,增强了土壤持水能力;粉碎秸秆同时降低了土壤稳定入渗速率,与对照相比减小了17.65%;(2)湿润锋推进深度与累积入渗量呈良好的线性关系;通过对3种入渗模型拟合发现,Philip模型和Kostiakov模型的拟合效果较好,符合黄土高原治沟造地土壤入渗率和时间的动态关系;(3)土壤水分蒸发过程中,添加粉碎秸秆具有阻截和蓄积土壤水分,提高土壤含水量的积极作用。     

黄土高原坝地深层土壤有机碳稳定性研究

淤地坝作为黄土高原重要的碳储库,其深层土壤有机碳稳定性在很大程度上影响坝地土壤储碳能力和碳排放。以黄土丘陵区不同利用年限的坝地为对象,从坝地剖面土壤有机碳含量及其组分入手,研究不同利用年限、不同沉积深度下,土壤有机碳含量及其稳定性的变化特征和影响因素。结果表明：（1）坝地深层土壤有机碳（SOC）含量低于该区坡耕地表层土壤有机碳含量,并未呈现明显的有机碳富集现象。随利用年限增加,坝地SOC含量呈增加趋势。（2）不同利用年限坝地的SOC、易氧化碳（EOC）、微生物量碳（MBC）、水溶性碳（DOC）含量呈现出明显的表聚现象。MBC、DOC和EOC含量在土壤0—60 cm内较高。（3）相较于坝地浅层土壤而言,坝地深层土壤有机碳具有较高的稳定性,长期耕作会降低坝地深层土壤有机碳稳定性。（4）坝地浅层和深层土壤有机碳稳定性变化的主导因素不同。浅层土壤有机碳稳定性主要受土层深度、有机碳含量和黏粒含量的影响,分别能解释其变异的50.4%,19.6%和11.8%;深层土壤有机碳稳定性主要受有机碳含量、土壤含水量和利用年限的影响,分别能解释其变异的38.9%,33.9%和11.8%。     

长期免耕和秸秆覆盖下黄土高原旱作土壤不同粒级复合体中酸解有机氮含量及分配比例变化

【目的】探明不同保护性耕作措施对黄土高原旱作土壤不同粒级复合体中有机氮含量与分配的影响,可对评价耕作措施的效果提供科学依据。【方法】基于黄土高原旱区14年的长期定位试验,采用Bremner法, 对传统耕作(T)、免耕(NT)、秸秆覆盖(TS)及免耕+秸秆覆盖(NTS)四种耕作措施条件下不同土壤粒级复合体中的有机氮含量和分配进行了研究。【结果】保护性耕作方式均增加了2~10 μm粒级土壤复合体的比例,增幅为20.0%~31.7%;降低了0~2 μm粒级土壤复合体在土壤中所占的比例,降幅为27.6%~31.0%。在所有耕作措施下,耕层土壤中不同粒级复合体所占的比例为10~50 μm＞2~10 μm＞0~2 μm＞50~100 μm＞100 μm。保护性耕作方式均明显提高了耕层0~2 μm粒级土壤复合体中氨基糖氮的含量,增幅在46.9%~107.1%,降低了单位质量0~2 μm粒级土壤复合体中的NH+4-N含量,降幅在14.8%~27.0%;明显提高了耕层单位质量2~10 μm粒级土壤复合体中酸解总氮、氨基酸氮和氨基糖氮的含量,增幅分别为8.2%~14.3%、16.2%~31.5%和154.9%~184.3%;降低了单位质量2~10 μm粒级土壤复合体中NH+ 4-N的含量,降幅为28.7%~46.6%。传统耕作(T)条件下,与各粒级土壤复合体相结合的有机氮量顺序为10~50 μm＞0~2 μm＞2~10 μm＞50~100 μm＞100 μm以上,而保护性耕作条件下,与各粒级土壤复合体相结合的有机氮量顺序为10~50 μm＞2~10 μm＞0~2 μm＞50~100 μm＞100 μm以上;与传统耕作相比,保护性耕作措施显著地增加了耕层土壤中酸解总氮、氨基酸氮、氨基糖氮的含量,增幅分别为6.6%~20.4%、89.0%~113.0%和11.9%~31.6%,降低了NH+4-N的含量。【结论】与传统耕作(T)处理相比,保护性耕作(NT、TS、NTS)措施明显提高了土壤2~10 μm粒级复合体的比例,降低了0~2 μm粒级复合体的比例;增加了耕层土壤中酸解氮总氮、氨基糖态氮和氨基酸态氮的含量,降低了NH+ 4-N的含量。土壤中以氨基酸态氮占优势地位,其它形态的有机氮无明显分布规律。