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.

Characteristics of Soil Organic Carbon, Total Nitrogen, and C/N Ratio in Chinese Apple Orchards

Soil organic carbon and nitrogen are used as indexes of soil quality assessment and sustainable land use management. At the same time, soil C/N ratio is a sensitive indicator of soil quality and for assessing the carbon and nitrogen nutrition balance of soils. We studied the characteristics of soil organic carbon and total nitrogen by investigating a large number of apple orchards in major apple production areas in China. High apple orchard soil organic carbon content was observed in the provinces of Heilongjiang, Xinjiang, and Yunnan, whereas low content was found in the provinces of Shandong, Henan, Hebei, and Shaanxi, with the values ranging between 6.44 and 7.76 g·kg-1. Similar to soil organic carbon, soil total nitrogen content also exhibited obvious differences in the 12 major apple producing provinces. Shandong apple orchard soil had the highest total nitrogen content (1.26 g·kg-1), followed by Beijing (1.23 g·kg-1). No significant difference was noted between these two regions, but their total nitrogen content was significantly higher than the other nine provinces, excluding Yunnan. The soil total nitrogen content for Xinjiang, Heilongjiang, Hebei, Henan, and Gansu was between 0.87 and 1.03 g·kg-1, which was significantly lower than that in Shandong and Beijing, but significantly higher than that in Liaoning, Shanxi, and Shaanxi. Six provinces exhibited apple orchard soil C/N ratio higher than 10, including Heilongjiang (15.42), Xinjiang (13.38), Ningxia (14.45), Liaoning (12.24), Yunnan (11.03), and Gansu (10.63). The soil C/N ratio was below 10 in the remaining six provinces, in which the highest was found in Shaanxi (9.47), followed by Beijing (8.98), Henan (7.99), and Shanxi (7.62), and the lowest was found in Hebei (6.80) and Shandong (6.05). Therefore, the improvement of soil organic carbon should be given more attention to increase the steady growth of soil C/N ratio.

Effects of soil nitrate:ammonium ratio on plant carbon:nitrogen ratio and growth rate of Artemisia sphaerocephala seedlings

Can soil nitrate： ammonium ratios influence plant carbon： nitrogen ratios of the early succession plant？ Can plant carbon： nitrogen ratios limit the plant growth in early succession？ To address these two questions, we performed a two-factor （soil nitrate： ammonium ratio and plant density） randomized block design and a uniform-precision rotatable central composite design pot experiments to examine the relationships between soil nitrate： ammonium ratios, the carbon： nitrogen ratios and growth rate of Artemisia sphaerocephala seedlings. Under adequate nutrient status, both soil nitrate： ammonium ratios and plant density influenced the carbon： nitrogen ratios and growth rate of A. sphaerocephala seedlings. Under the lower soil nitrate： ammonium ratios, with the increase of soil nitrate： ammonium ratios, the growth rates of plant height and shoot biomass of A. sphaerocephala seedlings decreased significantly; with the increase of plant carbon： nitrogen ratios, the growth rates of shoot biomass of A. sphaerocephala seedlings decreased significantly. Soil nitrate： ammonium ratios affected the carbon： nitrogen ratios of A. sphaerocephala seedlings by plant nitrogen but not by plant carbon. Thus, soil nitrate： ammonium ratios influenced the carbon： nitrogen ratios of A. sphaerocephala seedlings, and hence influenced its growth rates. Our results suggest that under adequate nutrient environment, soil nitrate： ammonium ratios can be a limiting factor for the growth of the early succession plant.

Determination of Atomic Fractions of Isotopes Carbon-13 and Nitrogen-15 Directly in Glicine, L-Leucine, Isoleucine and Alanine

Using compounds modified by the isotopes carbon-13 and nitrogen-15 helps conduct research in various fields of science, such as medicine, pharmacology, pharmacokinetics, metabolism, agriculture, and others. In the case of the availability of reliable, express, and cheap methods, the area of their use will gradually expand. A determination of the atomic fraction of the isotopes carbon-13 and nitrogen-15 directly in glycine, leucine, isoleucine, and alanine is proposed;the modification concerns all centers or one or more identical carbon and nitrogen centers separately, as well as both isotopes at the same time. There are defined mass lines of the mass spectrum of each amino acid, through which the isotopic content of carbon and nitrogen is calculated. The processes that must be taken into account for the determination of the isotopic content are also established. Isotopic analysis of these compounds until now was carried out by transforming them into carbon oxide, dioxide, and molecular nitrogen, and determination of their content in individual centers was impossible.

Effect of Different Fertilization Patterns on Carbon and Nitrogen Components of Tobacco Topsoil

In order to explore the fertilizing ways and dynamic changes of soil carbon and nitrogen in the main producing areas of tobacco in Guizhou,research was conducted to study the variations of dissolved organic carbon and nitrogen,total organic carbon and nitrogen and their ratio of tobacco-topsoil in organic fertilization pattern and conventional cultivation pattern （No fertilizer as control） by pot experiment.The results were as follows：（1） The effects of different fertilization patterns on soil dissolved organic carbon and nitrogen and total organic carbon and nitrogen were significantly different.The content of DOC,DON,TOC and TON in tobaccotopsoil was decreased with the advancing of growth period in conventional fertilization pattern.In the conventional fertilization pattern,the accumulation of DOC and TOC was increased first and then decreased,and the accumulation of DON and TON was decreased first and then increased.（2） The TOC content at the different growing stage and DOC content at the middle and later stage of tobacco were significantly improved in organic fertilization patterns.The accumulation of DON and TON in the conventional fertilization pattern was significantly higher than those in the organic fertilizer pattern and control at the rosette stage and vigorous stage.In the harvest period,the content of DOC,DON,TOC and TON of tobacco-topsoil in the conventional fertilization and organic fertilization pattern was significantly higher than those in the control.（3）The DOC/DON ratio and the TOC/TiON ratio was increased gradually with the advancing of growth period in conventional fertilization pattern,but they were increased first and then decreased in the organic fertilization pattern and CK.The DOC/DON and TOC/TON ratio of tobacco-topsoil in different fertilization patterns was showed as Y J＞ CK＞ CG at the different growing stage.The experiment results revealed that：The organic fertilization pattern may improve significantly the accumulation of DOC,DON,TOC and TON of tobacco-topsoil at the middle and later stage and the DOC/DON and TOC/TON ratio at the different growth stage.It contributed to the continuous and balanced supply of nutrients at the middle and later stage of tobacco and the soil fertility.

The Burial of Biogenic Silica, Organic Carbon and Organic Nitrogen in the Sediments of the East China Sea

We sampled the sediments of the East China Sea during 2005 and 2006, and analysed the contents of the biogenic matters: biogenic silica, organic carbon, and organic nitrogen. From the surface distribution we found the contents of these substances to be in the ranges of 0.72%-1.64%, 0.043%-0.82%, and 0.006%-0.11%, respectively. Their distributions were similar to each other, being high inside the Hangzhou Bay and low outside the bay. The vertical variations of the contents were also similar. In order to discuss the relation between them we analysed the variations of content with depth. They increased in the first 7 cm and then decreased with depth. The peaks were found at depths between 20 to 25 cm. The distribution of carbonate showed an opposite trend to that of biogenic matters. The content of total carbon was relatively stable with respect to depth, and the ratio of high organic carbon to carbonate showed a low burial efficiency of carbonate, which means that the main burial of carbon is organic carbon. In order to discuss the source of organic matters, the ratio of organic carbon to organic nitrogen was calculated, which was 8.01 to 9.65, indicating that the organic matter in the sediments was derived mainly from phytoplankton in the seawater.

Characteristics of soil organic carbon andtotal nitrogen storages for differentland-use types in Central Yunnan Plateau

Two-factor analysis of variance and redundancy analysis were used to analyze the characte-ristics of soil organic carbon total nitrogen storage in garden land,forestland,grassland,farmland,and bare land in the Dachunhe watershed of Jinning District,Kunming City,Yunnan Province,China.The effects of the soil organic carbon,total nitrogen stratification ratio,soil physical and chemical factors on the storage characteristics of organic carbon and total nitrogen of different land-use types were analyzed.The results show that the rates of carbon and nitrogen stratification in soil from 0-20 cm and 40-60 cm of the same land-use types differed are statistically significant(P<0.05).The organic carbon and total nitrogen stratification ratio SR1 of garden land soil are 38.5%and 25.3%,respectively,which are higher than SR^(2).The soil organic carbon and total nitrogen stratification ratio SR^(2) of different land-use types are greater than SR1.There are statistically significant differences in the SR^(2) soil organic carbon and total nitrogen stratification ratios(P<0.05).Soil organic carbon and total nitrogen storage of diffe-rent land-use types gradually decrease with increasing soil depth,with the maximum soil organic carbon and total nitrogen storage in the 0-20 cm soil layer.Soil organic carbon and total nitrogen sto-rage at the same soil depth are significantly different(P<0.05).Soil organic carbon and total nitrogen storage in the garden land are greater than those in the other land-use types.Soil organic carbon and total nitrogen storage in 0-20 cm garden land are 4.96 and 3.19 times than those in bare land,respectively;soil organic carbon and total nitrogen storage are explained by 93.66%and 1.53%in redundancy analysis RDA1 and RDA2,respectively.All physicochemical factors except Available Phosphorus and pH are statistically significance with carbon and nitrogen storage(P<0.05).Soil cationic exchange capacity,Available Phosphorus,C/N ratio,and Moisture Content are positively correlated with organic carbon and total nitrogen storage.In contrast,soil Bulk Density is negatively correlated with organic carbon storage and total nitrogen storage.Available Phosphorus,C/N ratio,and Moisture Content are the main factors promoting soil organic carbon and total nitrogen accumulation.

Growing Cover Crops to Improve Biomass Accumulation and Carbon Sequestration: A Phytotron Study

Cover crop system has shown a potential approach to improving carbon sequestration and environmental quality. Six of each winter and summer cover crops were subsequently grown in two soils, Krome gravelly loam soil (KGL), and Quincy fine sandy soil (QFS), in phytotrons at 3 temperatures (10/20, 15/25, 25/30oC for winter/summer cover crops) to investigate their contributions for carbon (C) sequestration. Among winter cover crops, the highest and the lowest amounts of C accumulated were by bellbean (Vicia faba L.), 597 g/m2 and white clover (Trifolium repens), 149 g/m2, respectively, in the QFS soil. Among summer cover crops, sunn hemp (Crotalaria juncea L.) accumulated the largest quantity of C (481 g/m2), while that by castorbean (Ricinus communis) was 102 g/m2 at 30oC in the KGL soil. The mean net C remained in the residues following the 127 d decomposition were 187 g/m2 of C (73% of the total) and 91 g/m2 (52% of the total) for the winter and summer cover crops, respectively. Following a whole cycle of winter and summer cover crops grown, the mean soil organic C (SOC) increased by 13.8 and 39.1% in the KGL and QFS soil, respectively, compared to the respective soils before. The results suggest that triticale, ryegrass, and bellbean are the promising winter cover crops in the QFS soil, while sunn hemp, velvetbean (Mucuna pruriens), and sorghum sudangrass (Sorghum bicolor &#215;S. bicolor) are recommended summer cover crops for both soils under favorable temperatures.

苏铁蕨在广东的分布概况及其中药饮片溯源分析

为给苏铁蕨(Brainea insignis)资源的保护和可持续利用提供依据,采用样线法对广东省内的苏铁蕨种群进行较全面的野外调查,测定稳定碳和氮同位素比值及碳和氮含量,对其中药饮片进行初步溯源。结果表明,苏铁蕨在广东主要分布在北江以东的惠州市、河源市、梅州市和深圳市;在北江以西分布较少;苏铁蕨分布点纬度为22°36'~24°39'N,经度为112°35'~116°48'E,海拔高度为26~706 m。2批次中药饮片的初步溯源结果显示,这些中药饮片可能源自广东罗浮山省级自然保护区、广东惠东莲花山白盆珠省级自然保护区和广东和平黄石坳省级自然保护区。

黄铁矿基MFC-CW耦合系统反硝化动力学研究

研究比较了黄铁矿基双阳极MFC-CW在不同碳氮比(0和2.5)及初始硝酸盐浓度(7、14和28 mg/L)条件下上阳极和下阳极的反硝化速率,以及对不同阶段硝酸盐还原反应动力学的模拟,从动力学角度揭示系统自养-异养协同反硝化机理。结果显示:不同碳氮比下系统两阳极硝酸盐还原效果差异不大,而亚硝酸盐累积、硫酸盐生成的差别较大,两阳极处微生物群落组成相似,优势菌属的相对丰度受C/N、阳极位置影响较大;两阳极处的硝酸盐还原动力学均属于一级反应,且C/N=0时反硝化速率常数(0.0087、0.0045和0.0188/h)均小于C/N=2.5(0.0151、0.0071和0.0798/h;以上阳极为例);MFC-CW系统的反硝化动力学更符合Monod-CSTR模型,且在停留时间较长时取得更好的拟合效果,随着停留时间的增加,C/N=0时系统的反硝速率增加,C/N=2.5时系统的反硝化速率在一定范围内波动[0.6662—0.7744 g/(m^(2)·d)]。实验结果可为黄铁矿基MFC-CW的实际工程应用提供理论指导。

铁碳微电解填料对人工湿地反硝化作用的影响

为探究铁碳微电解原理对人工湿地系统中反硝化作用的影响,利用液相还原法制得活性炭表面负载零价铁(Fe~0)材料,以填料不同投加配比,搭建垂直流人工湿地模拟小试装置,分别有1号纯砾石、2号砾石+3%铁碳、3号砾石+8%铁碳,观察每日进出水水质情况。结果表明:投加初期,2号与3号装置对硝态氮的去除效果显著,几乎可实现全部转化;填料表面Fe元素会伴随水流有一定损耗,且投加量越大损耗越高;两装置分别在18d和21d后出水水质达到稳定状态,硝态氮浓度稳定在11mg/L和13mg/L,略低于空白装置。

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。

水氮管理对黑土稻作土壤碳氮磷化学计量特征的影响

为阐明不同水氮管理模式对黑土稻作产量和土壤碳氮磷化学计量特征的影响,设置3种灌溉模式(常规淹灌、浅湿灌溉、控制灌溉)和4个氮肥梯度(0、85、110、135 kg/hm^(2)),探究了水稻产量、土壤碳氮磷含量及其化学计量比和层化率对不同水氮管理模式的响应规律。结果表明:与常规淹灌和浅湿灌溉相比,控制灌溉模式下,水稻通过形成足量大穗提高库容,小幅增加结实率,从而显著提高产量(P<0.05)。稻田土壤有机碳(SOC)、全氮(STN)、全磷(STP)含量随土层深度增加而降低,施氮处理可显著提升SOC、STN含量并降低STP含量(P<0.05)。与浅湿灌溉和控制灌溉相比,常规淹灌模式增加SOC、STN含量,而与常规淹灌和浅湿灌溉相比,控制灌溉模式增加STP含量。土壤C/N随施氮量增加而降低,土壤C/P、N/P随施氮量增加而升高,施氮能提升不同土层平均C/N层化率,降低C/P、N/P层化率。相比常规淹灌,控制灌溉模式能提升不同土层SOC、STP含量层化率,在一定程度上说明控制灌溉模式下配施适宜氮肥可以改善土壤质量。综合考虑,本研究中控制灌溉模式配施110 kg/hm^(2)氮肥为最优水氮管理方式。

A^(2)/O+反硝化深床滤池在城镇污水处理厂深度经济脱氮的运行优化

脱氮是当前城镇污水处理的重点,其中A^(2)/O+反硝化滤池工艺是生活污水处理主流工艺,四川省岷江流域某城镇污水处理厂通过优化进水流量分配比、调节溶解氧和内回流比、碳源筛选等工艺试验,综合考察了工艺调控措施对系统脱氮效能的提升以及脱氮成本的经济化控制。结果表明,A^(2)/O池进水100%进入厌氧区、内回流比200%、A^(2)/O池末端溶解氧控制在1.5 mg/L、反硝化深床滤池投加液体复合碳源,在有效深度脱氮的同时节约运行费用,总氮指标满足岷沱江标准,脱氮费用降低0.37元/m^(3)。

凋落物添加对蒿类荒漠草地土壤碳氮磷含量及其化学计量特征的影响

为探究凋落物添加对土壤养分及化学计量比的影响,本研究采用梅森瓶室外培养法,探求凋落物添加种类及添加量对蒿类荒漠草地0~10 cm土壤有机碳(SOC)、全氮(TN)、全磷(TP)及其化学计量比的影响,发现茎叶混合促进了凋落物分解,但同一添加物各添加量间分解速率无显著差异。添加5 g和7.5 g叶后土壤SOC较对照分别增加10.4%,15.2%(P<0.05)。土壤TN随叶添加量增加呈上升趋势,较CK增加11.9%~18.4%(P<0.05),而茎、茎叶混合依次仅在5 g、7.5 g添加量时显著减少7.9%、增加37.8%(P<0.05)。2.5 g茎叶、5 g茎和7.5 g叶添加后土壤TP较CK依次增加9.8%,14.4%,7.2%(P<0.05)。凋落物添加后土壤C∶N,C∶P,N∶P分别为2.46~3.63,12.40~16.17,3.47~5.60,且SOC与C∶P、TN与N∶P均呈正相关,而TN与C∶N除添加叶外均呈显著负相关。因此,凋落物分解有利于蒿类荒漠土壤养分的恢复,尤其是叶凋落物的分解是其土壤碳氮短期补充的重要来源。

不同温度下杉木凋落叶分解过程中碳氮磷释放及其化学计量比变化

[目的]研究升温对不同发育阶段杉木凋落叶分解过程中碳(C)、氮(N)、磷(P)释放规律及其生态化学计量特征的影响,揭示气候变暖背景下杉木人工林凋落叶分解过程中养分释放特征。[方法]收集中龄林(18年生)、成熟林(30年生)和过熟林(42年生)3个发育阶段的杉木凋落叶,设置25、30和35℃3个温度梯度进行室内模拟分解试验。[结果](1)在264 d的分解周期内,各发育阶段杉木凋落叶C、N、P残留率总体表现为随分解时间的增加而减小,但不同元素残留率变化模式不同,C残留率表现为释放—富集—释放模式,N残留率表现为富集—释放模式,P残留率表现为释放—富集模式。(2)拟合模型结果表明,成熟林与过熟林凋落叶分解过程中N周转期在35℃处理下比25℃处理分别缩短了34.4%和16.9%,P周转期分别缩短了38.4%和43.8%。(3)不同发育阶段杉木凋落叶分解过程中C:N、N:P比总体呈波动变化,C:P比呈先增大后减小的变化趋势,杉木凋落叶C:N、C:P、N:P比变幅分别为9.32~39.0、949~2194、32.7~153,升温处理在凋落叶分解过程总体上增大了C:P、N:P,降低了C:N比。[结论]温度升高能够缩短成熟林、过熟林凋落叶分解过程中N、P的周转期,提高各发育阶段杉木凋落叶分解过程中的C:P、N:P,说明杉木凋落叶分解明显受P限制,建议根据不同发育阶段杉木的生长需求,适当增加磷肥的施用。

克氏原螯虾碳、氮稳定同位素周转与分馏特征研究

为了解稳定同位素在克氏原螯虾(Procambarus clarkii)体内的周转与分馏特征,通过室内控制实验,研究了两种不同规格(虾种、成虾)克氏原螯虾在不同投饲条件下(饲料、鱼糜)的碳、氮稳定同位素周转半衰期和肌肉组织判别系数。结果表明,饲料组和鱼糜组虾种的生长系数分别为(0.0085±0.0007)d^(-1)、(0.0079±0.0012)d^(-1),成虾的生长系数分别为(0.0013±0.0001)d^(-1)、(0.0009±0.0004)d^(-1),不同投饲条件下克氏原螯虾生长系数差异不显著。虾种的相对增长率(1.60、1.57)大于成虾(1.08、1.05),不同投饲条件下克氏原螯虾相对增长率差异不大。相对于饲料组,鱼糜组虾种碳稳定同位素比值(δ^(13) C)在第7天出现显著差异,在28 d至56 d趋于稳定;成虾组δ^(13) C值在第14 d出现显著差异,在28 d至56 d趋于稳定;虾种和成虾氮稳定同位素比值(δ^(15) N)均在第14 d出现显著差异,在28 d至56 d趋于稳定。虾种碳稳定同位素周转速率(0.0208±0.0040)d^(-1)大于成虾(0.0184±0.0020)d^(-1)。虾种和成虾的碳同位素判别系数分别为0.89‰±0.15‰、1.06‰±0.16‰,氮同位素判别系数分别为3.42‰±0.08‰、3.63‰±0.13‰,虾种的碳同位素判别系数、氮同位素判别系数均小于成虾。研究结果可为应用碳、氮稳定同位素技术开展克氏原螯虾食性研究提供基础参数,提高食源分析的准确性。

江河源冻土区土壤碳氮空间分布特征及其影响因素

江河源区是我国高寒生态安全屏障的重要区域,冻土的长期存在使其形成低温冻结环境,弱化了土壤微生物活性,抑制了土壤有机质的矿化过程,因而其近地表浅层土壤碳氮含量高。然而,土壤碳氮含量对不同冻土分区和环境因素响应的空间分异规律尚不清楚。为此,针对江河源4个不同冻土区(季节冻土区、岛状多年冻土区、不连续多年冻土区、片状连续多年冻土区)共11个样点进行植被样方调查、土壤分层采样。在分析碳氮含量的基础上,探讨了年均地温(MAGT)、活动层厚度(ALT)、海拔(ASL)、土壤深度(SD)、植被特征及土壤pH对土壤有机碳(SOC)、全氮(TN)、碳氮比(C/N)的影响。结果表明:(1)SOC、TN、C/N在片状连续多年冻土区最高,在季节冻土区最低,且与年均地温负相关,和海拔正相关;(2)江河源区SOC、TN、C/N随土壤深度的增加而降低,自表层至40cm深度整体下降幅度分别为58.45%、36.96%、17.01%;(3)SOC、TN、C/N与植被覆盖度(FVC)显著正相关(P≤0.05),与土壤pH值显著负相关(P≤0.01);(4)冗余分析表明,土壤pH、MAGT、ALT、SD、FVC是影响江河源区SOC、TN、C/N空间分布的关键因素。研究结果可为厘清气候趋暖条件下江河源区土壤碳氮空间分异规律及多年冻土热稳定性对土壤碳氮排放的影响提供科学基础,同时也有助于预测多年冻土区土壤碳氮空间变化。

物料碳氮比及微生物菌剂接种量对黄瓜秧-鸡粪堆肥过程的影响

为明确黄瓜秧与鸡粪堆肥的适宜碳氮比及微生物菌剂接种量,本研究设计3个碳氮比(17.5、22.5和27.5)和3个微生物菌剂接种量(0.1%、0.2%、0.3%)共9个处理,测定了不同处理对黄瓜秧与鸡粪好氧堆肥过程中温度、有机质降解率、pH值、种子发芽指数(GI)、养分含量及堆肥腐熟度的影响。结果表明,高碳氮比和高微生物菌剂接种量处理堆体温度更快达到50℃以上,且堆肥过程中高温的峰值高于中、低碳氮比和中、低微生物菌剂接种量处理;高碳氮比和高微生物菌剂接种量处理,有机质降解率、堆肥的腐熟度(T)都显著提高;但接种0.3%微生物菌剂处理对有效磷、速效钾的保留效果以及堆肥最终发芽指数(GI)的提升均不如接种量为0.2%与0.1%的处理。综合上述分析,黄瓜秧与鸡粪进行堆肥无害化生产时,适宜的碳氮比为27.5,微生物菌剂接种量为0.1%~0.2%。

不同磷水平对土壤化学性质和棉花产量及其构成的影响

本研究探讨不同磷水平对北疆灰漠土棉田土壤化学性质和棉花产量及其构成的影响,为确定最佳施磷量和深入了解当前棉田肥力及棉花生产状况提供实践指导。以“国家灰漠土肥力与肥料效益监测站”已进行了5 a的棉田土壤磷素肥力演替特征定位施肥试验为研究对象,本研究对不施肥、不施磷、常规施化肥磷100%、化肥磷减施25%、化肥磷增施25%、化肥磷增施50%处理的土壤化学性质、磷素有效性特征和棉花产量及其构成进行分析。结果表明:随着施磷量的增加,有利于提升土壤养分含量。速效氮、有效磷、速效钾增幅分别在3.0%~16.10%、29.20%~111.77%、70.10%~72.10%之间,各速效养分含量依次与施肥初期相比,年均最高分别增长2.12、1.53、22.85 mg·kg^(-1)。全氮、全磷、全钾增幅分别在21.10%~35.10%、1.60%~54.0%、9.30%~10.90%之间,各全量养分含量依次与施肥初期相比,年均最高分别增长0.03、0.06、0.41 g·kg^(-1)。施磷150 kg·hm-2时,土壤有效磷含量和磷活化能力均显著最强,磷活化系数达2.13%,有效促进了土壤全磷向有效磷的转化。随着施磷量的增加,土壤有机质、有机碳含量均在施磷150 kg·hm^(-2)时显著提升,增幅均在11.86%~36.50%之间,有机质年均增长0.33 g·kg^(-1)左右,由于受北疆石灰性土壤自然特性和气候条件限制,结合碳氮磷比表明土壤有机质处于缺乏状态。对土壤p H和总盐分别呈下降和提升的趋势,范围分别在7.91~8.05和1.55~1.85 g·kg^(-1)之间,但效应均不显著。连续5 a施磷150 kg·hm^(-2),能在确保棉株整个生育时期养分需求的同时节约磷肥用量且对棉花增产效果最佳,籽棉产量可达4658 kg·hm^(-2),与不施肥、不施磷、常规施化肥磷100%相比,分别显著增产16.83%、15.01%、11.63%。本研究综合土壤养分、肥料投入、棉花产量指标,得出在北疆灰漠土棉田施磷150 kg·hm^(-2)较为可行。