Subsoil tillage enhances wheat productivity,soil organic carbon and available nutrient status in dryland fields

Tillage practices during the fallow period benefit water storage and yield in dryland wheat crops.However,there is currently no clarity on the responses of soil organic carbon(SOC),total nitrogen(TN),and available nutrients to tillage practices within the growing season.This study evaluated the effects of three tillage practices(NT,no tillage;SS,subsoil tillage;DT,deep tillage)over five years on soil physicochemical properties.Soil samples at harvest stage from the fifth year were analyzed to determine the soil aggregate and aggregate-associated C and N fractions.The results indicated that SS and DT improved grain yield,straw biomass and straw carbon return of wheat compared with NT.In contrast to DT and NT,SS favored SOC and TN concentrations and stocks by increasing the soil organic carbon sequestration rate(SOCSR)and soil nitrogen sequestration rate(TNSR)in the 0-40 cm layer.Higher SOC levels under SS and NT were associated with greater aggregate-associated C fractions,while TN was positively associated with soluble organic nitrogen(SON).Compared with DT,the NT and SS treatments improved soil available nutrients in the 0-20 cm layer.These findings suggest that SS is an excellent practice for increasing soil carbon,nitrogen and nutrient availability in dryland wheat fields in North China.

Effects of Long-Term Winter Planted Green Manure on Distribution and Storage of Organic Carbon and Nitrogen in Water-Stable Aggregates of Reddish Paddy Soil Under a Double-Rice Cropping System

In agricultural systems, maintenance of soil organic matter has long been recognized as a strategy to reduce soil degradation. Manure amendments and green manures are management practices that can increase some nutrient contents and improve soil aggregation. We investigated the effects of 28 yr of winter planted green manure on soil aggregate-size distribution and aggregateassociated carbon（C） and nitrogen（N）. The study was a randomized completed block design with three replicates. The treatments included rice-rice-fallow, rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass. The experiment was established in 1982 on a silty light clayey paddy soil derived from Quaternary red clay（classified as Fe-Accumuli-Stagnic Anthrosols） with continuous early and late rice. In 2009, soil samples were collected（0-15 cm depth） from the field treatment plots and separated into water-stable aggregates of different sizes（i.e., 〉5, 2-5, 1-2, 0.5-1, 0.25-0.5 and 〈0.25 mm） by wet sieving. The long-term winter planted green manure significantly increased total C and N, and the formation of the 2-5-mm water-stable aggregate fraction. Compared with rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass, the rice-rice-fallow significantly reduced 2-5-mm water-stable aggregates, with a significant redistribution of aggregates into micro-aggregates. Long-term winter planted green manure obviously improved C/N ratio and macro-aggregate-associated C and N. The highest contribution to soil fertility was from macro-aggregates of 2-5 mm in most cases.

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.

Contents of soil organic carbon and nitrogen in water-stable aggregates in abandoned agricultural lands in an arid ecosystem of Northwest China

Soil organic matter content in water-stable aggregates（WSA） in the arid ecosystems（abandoned agricultural lands especially） of China is poorly understood. In this study, we examined the WSA sizes and stability, and soil organic carbon（OC） and nitrogen（N） contents in agricultural lands with abandonment ages of 0, 3, 12, 20, 30 and 40 years, respectively, in the Minqin Oasis of Northwest China. The total soil OC and N contents at depths of 0–20, 20–40 and 40–60 cm in abandoned agricultural lands were compared to those in cultivated land（the control）. Agricultural land abandonment significantly（P0.25 mm） as the age of agricultural land abandonment increased. The effect of abandonment ages of agricultural lands on MWD was determined by the changes of OC and N accumulation in WSA sizes ＆gt;2 mm. The total OC and N contents presented a stratification phenomenon across soil depths in this arid ecosystem. That is, both of them decreased significantly at depths of 0–20 and 40–60 cm while increased at the depth of 20–40 cm. The WSA sizes ＆lt;0.053 mm had the highest soil OC and N contents（accounting for 51.41%–55.59% and 42.61%–48.94% of their total, respectively）. Soil OC and N contents in microaggregates（sizes 0.053–0.25 mm） were the dominant factors that influenced the variations of total OC and N contents in abandoned agricultural lands. The results of this study suggested that agricultural land abandonment may result in the recovery of WSA stability and the shifting of soil organic matter from the silt＋clay（＆lt;0.053 mm） and microaggregate fractions to the macroaggregate fractions. However, agricultural land abandonment did not increase total soil OC and N contents in the short-term.

Nitrogen-doped hierarchical porous carbon from polyaniline/silica self-aggregates for supercapacitor

In this paper, nitrogen-doped hierarchical porous carbon(N-HPC) was prepared from polyaniline(PANI)/silica self-aggregates. H-bonding between N\\H groups in aniline/PANI and \\OH groups in nano silica template led to a self-assembly type, which enabled the formation of uniform N-HPC nanoparticles. Silica self-aggregates provided macroporous channels resulted in a decreased diffusion distance. After removing the hard template,the N-HPC had a high surface area(899 m^2·g^(-1)). Owing to two co-existed synergetic energy-storage mechanisms and the hierarchical porous structure, the obtained N-HPC exhibited a high specific capacitance of 218.75 F·g^(-1) at 0.5 A·g^(-1), compared with the nonporous nitrogen-doped carbon(N-C) derived from pure PANI. Moreover, the N-HPC electrode demonstrated excellent cycle life, retaining 99% of its initial specific capacitance after 1000 cycles.

Aggregate stability and associated C and N in a silty loam soil as affected by organic material inputs

To make recycling utilization of organic materials produced in various agricultural systems, five kinds of organic materials were applied in a field test, including crop straw （CS）, biogas residue （BR）, mushroom residue （MR）, wine residue （WR）, pig manure （PM）, with a mineral fertilizer （CF） and a no-fertilizer （CK） treatment as a control. Our objectives were： i） to quantify the effects of organic materials on soil C and N accumulation; ii） to evaluate the effects of organic materials on soil aggregate stability, along with the total organic carbon （TOC）, and N in different aggregate fractions; and iii） to assess the relationships among the organic material components, soil C and N, and C, N in aggregate fractions. The trial was conducted in Wuqiao County, Hebei Province, China. The organic materials were incorporated at an equal rate of C, and combined with a mineral fertilizer in amounts of 150 kg N ha^-1, 26 kg P ha^-1 and 124 kg K ha-1 respectively during each crop season of a wheat-maize rotation system. The inputted C quantity of each organic material treatment was equivalent to the total amount of C contained in the crop straw harvested in CS treatement in the previous season. TOC, N, water-stable aggregates, and aggregate-associated TOC and N were investigated. The results showed that organic material incorporation increased soil aggregation and stabilization. On average, the soil macroaggregate proportion increased by 14%, the microaggregate proportion increased by 3%, and mean-weight diameter （MWD） increased by 20%. TOC content followed the order of PM〉WR〉MR〉BR〉CS〉CK〉CF; N content followed the order WR〉PM〉MR〉BR〉CS〉CF〉CK. No significant correlation was found between TOC, N, and the quality of organic material. Soil silt and clay particles contained the largest part of TOC, whereas the small macroaggregate fraction was the most sensitive to organic materials. Our results indicate that PM and WR exerted better effects on soil C and N accumulation, followed by MR and BR, suggesting that organic materials from ex situ farmland could promote soil quality more as compared to straw returned in situ.

长期不同施氮量下黑土团聚体稳定性及有机碳含量的变化

为测定不同氮肥施用量对黑土团聚体组成及稳定性、有机碳含量及团聚体有机碳分布的影响,阐明黑土有机碳稳定性对不同施氮水平的响应机制,本研究在吉林省梨树县不同施氮水平长期定位试验田进行取样,以施氮水平不同设置5个处理,分别为T1(0)、T2(160 kg·hm^(-2))、T3(240 kg·hm^(-2))、T4(280 kg·hm^(-2))、T5(320 kg·hm^(-2)),分析长期不同施氮量下水稳性团聚体组成、团聚体结构特征、土壤总有机碳含量及团聚体有机碳分布的变化,探究酸化黑土有机碳含量影响特征。结果表明:随氮肥施用水平的升高,土壤碱解氮(AN)和全氮(TN)含量先增后减,T3处理含量最高,AN和TN分别比T1处理高24.90%、10.28%;土壤速效磷(AP)的含量呈下降趋势。随氮肥用量的提高,土壤团聚体呈现大粒径团聚体向小粒径团聚体转变的趋势,>2 mm粒径团聚体下降14.55%。土壤有机碳总量随施氮水平的提高呈先增后减的趋势,施氮量为280 kg·hm^(-2)有机碳含量最高;>2 mm和2~0.25 mm粒径团聚体有机碳含量较高;不同施氮水平下有机碳含量与团聚体稳定性特征的几何平均直径、土壤团聚体破坏率、不稳定团粒指数和土壤化学性质的相关度较高。研究表明:通过13 a连续施入不同水平氮肥,土壤有机碳含量随氮肥施用量的增加呈先增后减的趋势;氮肥施用量增加会显著降低土壤pH,土壤团聚体有机碳主要分布在2~0.25 mm粒径中。

人工修复边坡植被演替初期有机碳组分及土壤生态化学计量特征

[目的]研究人工修复边坡演替初期土壤有机碳组分、碳氮磷含量及其化学计量比,揭示气候因子对人工修复边坡演替初期土壤有机碳组分、碳氮磷含量及其化学计量比的影响,以期为后期人工修复边坡的养护提供指导和建议,确保人工修复边坡的正向演替。[方法]在湛江、梧州、宜昌、南阳、焦作、潍坊、加查采集了初期基材配制相同、植物配制相近,修复年限为2~4年的植被混凝土人工修复边坡土样,通过实验获得土样有机碳组分、碳、氮、磷的数据,采用冗余分析,开展气候因子对人工修复边坡演替初期土壤有机碳组分、碳氮磷含量及其化学计量比的影响研究。[结果]人工修复边坡演替初期F_(1)含量的变化范围为1.10~3.64 g/kg;F_(2)含量的变化范围为1.33~3.04 g/kg;F_(3)含量的变化范围为2.02~3.34 g/kg;F_(4)含量的变化范围为10.86~15.24 g/kg;TOC含量变化范围为15.52~24.71 g/kg;TN含量变化范围为0.61~0.93 g/kg;TP含量的变化范围为0.81~1.22 g/kg;C∶N变化范围为23.55~27.95;C∶P变化范围为17.26~23.09;N∶P的变化范围为0.72~0.98;C∶N∶P的变化范围为17.26∶0.75∶1~24.81∶0.95∶1。[结论]演替初期人工修复边坡碳磷表现为中等及以上,氮表现为缺乏;有机碳组分以惰性有机碳为主且有机碳稳定性较强。有机碳组分的主要影响因子为年平均温度、物种丰富度和年平均降水;土壤碳氮磷含量及其化学计量比主要影响因子为年平均温度、物种丰富度、pH和容重。

细粒尾矿无土修复后土壤有机碳累积特性

铜等大宗尾矿无土化原位修复是尾矿资源化、无害化利用的有效途径。修复后土壤养分蓄积直接关系到后期田间管理,对其有机碳等重要养分积累规律研究至关重要。针对我国湖北某细粒铜尾矿修复场地进行研究,对未经修复、修复一年与修复两年的0~15、15~30、30~45 cm三种深度的土壤进行取样,对总有机碳、易氧化态有机碳、颗粒态有机碳、矿物结合态有机碳、可溶性有机碳与微生物量有机碳6种土壤有机碳形态进行测定并分析其变化规律。结果表明:经无土修复后的细粒尾矿土在无外源有机物的添加下依然会进行土壤总有机碳的积累;尾矿进行有机碳积累的主要方式是以矿物结合态有机碳为代表的惰性有机碳的增加,惰性碳的升高有助于固定有机碳;尾矿的团聚体粒径尺寸与土壤总有机碳的含量呈正相关,其中惰性有机碳更偏好聚集在粒径较小的团聚结构中,土壤碳库活性逐渐增强,更容易发生有机碳的转化;对尾矿土进行修复后土壤有机碳含量有显著提高,且主要以惰性有机碳的形式积累,在该场地表现出了巨大的碳汇潜力。该研究同时明确了该场地修复后矿区土壤有机碳各形态的累积特性,可为指导尾矿修复工作提供数据支持。

氮、磷添加对亚热带毛竹林土壤水稳性团聚体及有机碳分布的影响

[目的]研究氮(N)、磷(P)添加对亚热带毛竹林土壤水稳性团聚体及土壤有机碳(SOC)分布的影响,揭示毛竹林SOC对N、P添加的响应特征,为N沉降背景下毛竹林固碳增汇提供数据支持。[方法]以NH_(4)NO_(3)为N源、NaH_(2)PO_(4)为P源,设置不同N、P添加量的4个处理:CK(0 kg·hm^(-2)a^(-1)N+0 kg·hm^(-2)a^(-1)P)、N(120 kg·hm^(-2)a^(-1)N)、P(120 kg·hm^(-2)a^(-1)P)和NP(120 kg·hm^(-2)a^(-1)N+120 kg·hm^(-2)a^(-1)P),3年后分析N、P添加对毛竹林土壤0~20、20~40和40~60 cm土层不同粒级(>2、0.25~2、0.053~0.25和<0.053 mm)团聚体含量、平均重量直径(MWD)、几何平均直径(GMD)及其SOC分布的影响。[结果]1)各土层土壤水稳性团聚体均以大团聚体(>0.25 mm)为主,各处理大团聚体含量均随土层加深而降低,微团聚体(<0.25mm)含量随土层加深而增加。在0~20cm土层,N处理显著增加微团聚体含量,对大团聚体含量无显著影响;P处理对团聚体组成无显著影响;NP处理显著增加微团聚体含量、降低大团聚体含量;各处理对水稳性团聚体MWD和GMD均无显著影响。在20~40和40~60cm土层,与CK相比,各处理均呈大团聚体含量降低、微团聚体含量增加的趋势。在20~40 cm土层,P处理显著降低水稳性团聚体MWD和GMD,N处理对水稳性团聚体MWD和GMD无显著影响,NP处理显著降低水稳性团聚体MWD,对水稳性团聚体GMD无显著影响;在40~60 cm土层,各处理均显著降低水稳性团聚体MWD和GMD。2)与CK相比,N、P处理显著降低各土层SOC含量;NP处理对0~20和20~40 cm土层SOC含量均无显著影响,但显著降低40~60 cm土层SOC含量。3)N处理对0~20和40~60cm土层土壤团聚体SOC贡献率均无显著影响,仅增加20~40cm土层土壤大团聚体SOC贡献率、降低微团聚体SOC贡献率;NP处理显著降低各土层大团聚体SOC贡献率、增加微团聚体SOC贡献率;P处理对团聚体SOC贡献率的影响在20~40和40~60 cm土层与NP处理对其的影响趋势一致,对0~20 cm土层无显著影响。[结论]N、P同时添加可在一定程度上减缓N或P单独添加引起的毛竹林SOC含量降低;P添加可促进SOC由大团聚体向微团聚体转移,增加SOC稳定性。在N素相对富集、P限制的亚热带森林土壤中,P添加可缓解N沉降引起的SOC含量降低,并在一定程度上促进SOC固定。

柑橘大豆间作对土壤团聚体结构及其有机碳、氮分布的影响

探讨柑橘大豆不同间作年限下土壤团聚体结构及有机碳、氮分布差异,旨在为果园土壤改良提供参考。通过田间定位试验设置清耕区(CK)、柑橘间作大豆1年(T1)、柑橘间作大豆2年(T2)和柑橘间作大豆3年(T3)4个处理,测定土壤团聚体组成、稳定性、有机碳和全氮等指标。结果表明:①与清耕柑橘园相比,柑橘间作大豆的土壤>0.25 mm大团聚体含量提高了19.58%~22.29%;②柑橘间作大豆的土壤团聚体稳定性特征表现为:T3>T2>T1>CK;③团聚体粒径中的有机碳和全氮含量表现为>5 mm粒径最高,<0.25 mm粒径含量最低,柑橘间作大豆的土壤C/N值较清耕区提高了1.16倍~1.19倍;④土壤团聚体组成与团聚体有机碳和全氮含量的相关性显著,RDA分别解释99.32%和94.99%的差异信息,其中>5、5~2和0.5~0.25 mm粒径土壤团聚体是影响土壤有机碳和全氮含量变化的主要环境因子。总体而言,柑橘园行间间作大豆可增加土壤肥力,改善土壤团聚体结构,是一种可持续农业发展模式。

氮磷添加对常绿阔叶林土壤团聚体有机碳及其与磷组分相关的影响

[目的]为探究磷输入如何调节大气氮沉降对土壤团聚体有机碳含量及碳与磷关系的影响。[方法]在常绿阔叶林土壤建立长达6年(2015-2021年)的养分添加长期监测试验平台,包括4个处理:对照[P0+N0,P0 kg/(hm^(2)·a)+N0 kg/(hm^(2)·a)]、氮添加[P0+N100,P0 kg/(hm^(2)·a)+N100 kg/(hm^(2)·a)]、磷输入[P50+N0,P50 kg/(hm^(2)·a)+N0 kg/(hm^(2)·a)]以及氮磷同时输入[P50+N100,P50 kg/(hm^(2)·a)+N100 kg/(hm^(2)·a)],各处理设3次重复,共计12个样地。于2021年8月采集样地0-10 cm土层土壤样品,测定基础理化性质、土壤粒径分布规律、不同粒径土壤团聚体磷组分及有机碳(SOC)含量。[结果](1)P0处理下,氮添加显著增加大团聚体占比,减少黏粒和粉粒含量,提高各团聚体粒径中SOC含量;氮添加分别显著降低和增加团聚体黏粒、粉粒中易分解态磷组分(LP)和难分解态磷组分(RP)含量。(2)P50处理下,氮添加显著提高土壤团聚体平均几何直径(GMD),对各粒径团聚体中磷组分和SOC含量均无显著影响。(3)P0处理下,土壤团聚体SOC与难分解态磷呈正相关关系;P50处理下,土壤团聚体SOC与各功能磷组分无显著相关。由此推断,P0处理下,氮添加通过提高常绿阔叶林土壤团聚体黏粒、粉粒径中难分解态磷而增加土壤有机碳的固持;P50处理下,氮添加对各粒径中有机碳的影响可能受到生物因素的调节,与磷的有效性无关。[结论]氮沉降对常绿阔叶林土壤团聚体中碳磷内在关系的影响受到磷的调控,研究结果为森林土壤碳循环应对全球气候变化提供数据支撑。

赖草草地叶片养分、碳组分和防御性化合物对氮添加的响应

本研究依托山西右玉黄土高原赖草(Leymus secalinus)草地2017年建立的氮(Nitrogen, N)添加梯度试验平台(0~32 g·m^(-2)·a^(-1)),探究N添加对优势植物赖草叶片养分[N、磷(Phosphorus, P)、钾(Potassium, K)]、非结构性碳水化合物、结构性碳水化合物和防御性化合物含量的影响。结果表明:N素输入显著提高叶片N,K含量和N∶K和N∶P比值,降低叶片P含量和P∶K比值;N素输入显著降低叶片非结构性碳水化合物和结构性碳水化合物含量;N素输入显著增加叶片总酚、单宁和黄酮类化合物含量;PCA分析表明低N(≤8 g·m^(-2)·a^(-1))和高N(>8 g·m^(-2)·a^(-1))输入下赖草叶片性状存在显著差异,土壤无机N含量、土壤有效N∶P和N∶K是其主要影响因子。以上结果表明N素输入改变了盐渍化草地赖草叶片养分-碳组分-防御性化合物的分配策略。

基于近红外光谱技术的水稻节间主要碳氮代谢组分分析

近年来,近红外光谱技术在作物样品组分检测和育种材料快速筛选等方面得到广泛应用,而关于水稻源库器官,尤其是水稻节间主要碳氮代谢组分高通量检测的研究鲜见报道。本研究以试验获得的576份代表性节间样本为材料,在获得样本化学实测值的基础上,采集样本的近红外光谱信息,并利用偏最小二乘(partial least square,PLS)法构建水稻节间主要碳氮代谢组分蔗糖、淀粉、总氮模型。模型验证结果显示:水稻节间蔗糖、淀粉、总氮含量PLS模型验证集决定系数分别为0.988、0.977和0.957,相对分析误差均大于3,模型的性能指数分别为85.20、85.80和86.50,表明所建模型预测结果准确可靠。此外,水稻叶片和叶鞘的淀粉、总氮含量和碳氮比的PLS模型也具有较高的精度。本研究构建了水稻节间主要碳氮代谢组分的近红外光谱模型,为水稻栽培生理和高产栽培理论研究提供了技术支撑。

不同连栽代次桉树人工林土壤团聚体中有机碳组分的积累和转化

【目的】探究不同连栽代次桉树人工林土壤中有机碳组分的积累与转化特征,以期揭示环境因素对土壤有机碳组分积累和转化过程的影响,进而为提高桉树生产力和土壤管理提供科学依据。【方法】以广西博白县博白林场第1、2、3代桉树人工林为研究对象,采用干筛法将收集的0~40 cm土壤分为>2 mm、1~2 mm、0.25~1 mm和<0.25 mm粒径的团聚体以评估土壤团聚体稳定性,并测量不同团聚体中有机碳组分(包括活性有机碳、缓性有机碳和惰性有机碳)的含量和储量,利用冗余分析和偏最小二乘法结构方程模型揭示影响土壤有机碳积累和转化的关键因素。【结果】(1)连栽显著降低了土壤团聚体的稳定性和各有机碳组分的含量和储量。(2)土壤各有机碳组分含量随团聚体粒径的增加而下降,而储量的分布规律则相反。(3)冗余分析和偏最小二乘法结构方程模型证明,土壤团聚体稳定性是影响土壤有机碳积累的主要因素,连栽抑制了惰性有机碳向活性有机碳的转化,导致土壤有机碳总体有效性下降。【结论】连栽主要通过改变土壤团聚体的分布和稳定性,进而调控桉树人工林土壤有机碳组分的积累和转化。研究结果有助于理解桉树人工林土壤有机碳的积累和转化过程中土壤团聚体调控机制。

史河沙地人工林套种花生对土壤碳氮组分的影响

【目的】探究套种花生对史河沙地3种常见人工林土壤碳氮组分的影响,为豫东南史河沙地生态修复工程的林农植物选择配置模式提供科学依据。【方法】选取史河沙地栾树单种、五角枫单种、杨树单种、栾树套种花生、五角枫套种花生以及杨树套种花生6种林分类型为研究对象,通过采集各林分0~20 cm、20~40 cm和40~60 cm土层土壤进行检测,分析不同林分和不同土层之间人工林套种花生对土壤碳氮组分的影响。【结果】①在垂直方向上,6种林分的土壤碳氮各组分含量均随着土层的增加而下降,同一土层不同林分碳氮组分含量之间差异显著(P<0.05)。在水平方向上,6种林分的土壤碳氮各组分含量基本表现为套种高于单种。②在浅层土壤中,栾树套种花生的土壤碳氮组分含量均为最高,而五角枫单种的含量均为最低。③相关性分析表明,TN与SOC呈极显著正相关关系(P<0.01);土壤POC、EOC等活性有机碳组分和SOC呈显著正相关(P<0.05);MBN和TN及其他氮组分均呈极显著(P<0.01)或显著(P<0.05)正相关关系。【结论】林农套种模式有利于提高沙地人工林的碳氮含量,栾树套种花生模式对史河沙地耕层土壤碳氮含量改善效果最佳。

石漠化土壤碳矿速率对丛枝菌根真菌接种的响应

为探明丛枝菌根(Arbuscular mycorrhiza,AM)真菌接种对石漠化土壤碳矿化影响的过程及机制,选择圆柏(Sabina chinensis)为供试寄主植物,分别接种幼套近明球囊霉(Claroideoglomus etunicatum,CE)、摩西斗管囊霉(Funneliformis mosseae,FM)、根内根孢囊霉(Rhizophagus intraradices,RI),设对照处理(无AM真菌,CK),采用室内需氧培养法测定不同处理土壤碳矿化速率的时空变化,分析其与根系侵染状况、微生物生物量碳氮和土壤性质的关系。结果表明,1)3种AM真菌接种对土壤碳矿化速率的影响存在差异。CE处理下的碳矿化速率(13.1 mg·kg^(-1)·d^(-1))高于RI(11.7 mg·kg^(-1)·d^(-1))和FM(9.7 mg·kg^(-1)·d^(-1));3种AM真菌处理下碳矿化速率均表现为湿季大于干季,沿土层加深而减小,随季节和土层的变幅均呈现CE>RI>FM的特征。2)AM真菌接种显著提高根系侵染率、菌丝侵染密度、土壤碳氮磷组分和水分含量,其提升率变幅范围为16.4%-81.6%。3)AM真菌接种引起土壤微生物量碳和氮含量变化显著影响碳矿化,其对碳矿化速率的解释量大小为:CE(93.3%､87.6%)>RI(86.4%､80.7%)>FM(81.1%､75.1%)>CK(65.2%、67.6%)。4)AM真菌处理下碳矿化速率与根系侵染率、菌丝侵染密度、易氧化碳、有机碳、全磷、全氮和含水率呈显著正相关,与容重和pH呈显著负相关;主成分结果表明,易氧化有机碳、微生物量碳氮、容重是土壤碳矿化速率的主要影响因子。因此,AM真菌共生主要通过改变碳组分、微生物量氮及土壤紧密度,进而促进云南石漠化土壤碳矿化速率。

红壤丘陵区种植茶树和柑橘对土壤肥力和水土流失的影响

为探讨经济林种植对土壤肥力和水土保持的影响,以浙江省常山县红壤丘陵区种植茶树和柑橘10年后的园地为对象,并以祼地为对照,定位研究了水土流失量,采样并分析了0~10 cm土壤容重、孔隙度、速效氮磷钾和不同团聚体组分碳氮含量。结果表明:种植茶树和柑橘10年后,土壤容重显著下降(P<0.05),土壤孔隙度、田间持水量、有机碳、有效磷、速效钾和碱解氮含量显著提高(P<0.05);土壤大团聚体有机碳含量大小排序为柑橘园>茶园>祼地,土壤中团聚体、微团聚体、粉粒的有机碳、氮含量大小表现均为茶园>柑橘园>裸地,不同处理间的差异达显著水平(P<0.05);茶园土壤黏粒有机碳、氮含量显著高于柑橘园、祼地(P<0.05);与祼地相比,柑橘园和茶园年径流深显著降低了87.66%、92.25%(P<0.05),年土壤流失量显著减少了95.93%、98.78%(P<0.05)。试验区年径流深、年土壤流失量与土壤有机碳、总孔隙度、田间持水量之间具有极显著或显著负相关(P<0.01,P<0.05),与土壤容重具有显著正相关(P<0.05)。综上,茶树和柑橘种植有利于提高土壤肥力,降低水土流失,其中种植茶树的效果优于柑橘。

有机肥等氮量替代化肥对稻麦轮作水稻土有机碳矿化特征的影响

采用大田试验和室内培养试验相结合的方法,研究有机肥等氮量替代化学氮肥对稻麦轮作模式下土壤有机碳赋存转化及功能酶活性的影响。结果表明:连续3年有机肥等氮量替代化学氮肥后土壤有机碳含量提高2.0%~17.5%,全氮含量提高1.4%~30.5%。替代10%最有利于提升>2.00和<0.053 mm团聚体中有机碳和全氮含量,替代40%最有利于提升0.25~2.00和0.053~0.25 mm团聚体中有机碳和全氮含量。有机肥等氮量替代化学氮肥各处理土壤有机碳矿化速率整体上高于仅施化学氮肥处理,其中替代30%、40%最有利于提升土壤有机碳累积矿化量,前者也最有利于提升土壤有机碳矿化率。有机肥等氮量替代化学氮肥处理会导致土壤外切-β-1,4-葡聚糖酶/纤维二糖苷酶(S-C1酶)活性下降,替代20%最有利于提升土壤蔗糖酶和β-葡萄糖苷酶活性,替代50%最有利于提升土壤酸性磷酸酶活性。综上,有机肥等氮量替代化学氮肥可显著提高土壤0.025~2.00和>2.00 mm团聚体碳氮含量,土壤有机碳含量与土壤全氮含量以及β-葡萄糖苷酶与土壤蔗糖酶呈显著正相关,替代20%有利于土壤有机碳矿化,替代40%有利于土壤碳固定。

施氮和灌溉处理对麦田土壤有机碳组分及酶活性的影响

探讨不同水氮管理对麦田土壤有机碳(SOC)含量、SOC组分及土壤酶活性的影响,对促进SOC库提升和助力“双碳”目标实现具有重要作用。试验设置雨养和灌溉2个灌水处理及3个施氮水平(分别为0、180和360 kg/hm^(2),记为N0、N180和N360),共6个处理。于小麦收获期,测定0~40 cm土层SOC、易氧有机碳(EOC)、颗粒有机碳(POC)和矿质结合有机碳(MOC)含量,以及土壤脲酶(UA)、β-葡萄糖苷酶(β-BG)、蔗糖酶(IA)、过氧化氢酶(HPA)活性。结果表明:与雨养条件下相比,灌溉条件下会降低SOC含量,不利于维持SOC的稳定;N180处理下,与灌溉条件下相比,雨养条件SOC含量在0~20和20~40 cm土层中分别提高了6.3%和71.7%;并且在3个氮水平下,雨养条件下的EOC含量均高于灌溉条件。研究显示,施氮180 kg/hm^(2)结合适宜的水分管理有利于促进SOC积累。适宜农田水氮管理不仅是实现作物单产提升的重要途径,在促进SOC库提升和助力实现“双碳”目标方面也发挥着重要作用。