不同生物炭对安徽宣城旱地红壤氮矿化的影响

采用连续间隙淋洗培养法,研究了竹炭、烟草秸秆炭及棉花秸秆炭对安徽宣城旱地红壤氮素矿化作用的影响。结果表明:3种生物炭均可提高土壤p H,但p H增长幅度与生物炭用量相关,最高可增加2个单位;不同用量的生物炭添加都会导致土壤氮素硝化速率及矿化速率的降低,竹炭、烟草秸秆炭及棉花秸秆炭分别使硝化速率最大降幅达49.2%、72.3%与69.2%,矿化速率最大降幅达33.7%、61.9%与61.1%。因此,生物炭实际施用需作谨慎的评估,优化其使用方法。     

水分因素对绿洲荒漠过渡带土壤氮矿化的影响

通过树脂芯原位培养试验,分析水分因素对塔里木绿洲荒漠过渡带3种不同植被覆盖度(LCD:0~0.2;MCD:0.2~0.4;HCD:0.4~0.6)土壤矿质氮含量影响及氮矿化速率变化。结果表明,水分对土壤氮矿化作用有明显影响,土壤净氮矿化速率与土壤水分有明显相关性,3种植被覆盖度类型的剖面水分变化和净氮矿化速率呈正相关,相关系数LCD是0.866 9(P0.01),MCD是0.647 9(P0.05),HCD是0.594 0(P0.05);测定周期内绿洲荒漠过渡带土壤平均净氮矿化速率,LCD为0.334kg/(hm2·d),MCD为1.010kg/(hm2·d),HCD为0.998kg/(hm2·d);该区域土壤水分变化是影响氮矿化的主要因素之一,说明在极端干旱条件下,水分控制氮矿化作用,但随植被覆盖度递增土壤含水量增加,水分因素对土壤氮矿化作用逐渐递减。     

Comparison of Different Models to Simulate Soil Temperature and Moisture Effects on Nitrogen Mineralization in the Soil

The rate of mineralization of organic nitrogen (N) in soils depends on environmental factors, specially temperature and water content. In this paper, different models that describe temperature and water content effects on mineralization are examined and the values of the factors used in the different models are compared. The results of mineralization simulations, using the different models at different levels of water content and temperature, are compared with experimental field data from the literature. The results show that the principal differences are found at temperatures greater than 25°C and at water content levels near saturation and near permanent wilting point. The different models were used for an estimation of net mineralized N under field conditions in a soil with ryegrass by using a deterministic model of water and N transport in the soil. The results confirm the differences of moisture and temperature effects on mineralization when the soil became very dry and wet during the rainy months.     

土壤水分和氮添加对3种质地紫色土氮矿化及土壤pH的影响

为正确认识土壤水分、质地和外源氮添加对紫色土氮矿化作用和土壤pH的影响,以西南地区典型的紫色土为研究对象,通过90d的室内恒温(25℃)好气培养,研究了3种质地(粘土、粉粘壤土和砂土)紫色土在不同含水量(55%,65%和75%田间持水量)和尿素氮添加水平(0mg/kg土和250mg/kg土.)条件下,土壤氮矿化作用和pH的变化。结果表明:前30d的累积矿化氮量可占培养期间(90d)的78.48%~91.55%,且各处理的土壤累积矿化氮量和净矿化速率均随着培养时间的延长而快速增加;第30~90d,土壤累积矿化氮量增长缓慢,净矿化速率迅速下降并趋于稳定。土壤累积矿化氮量和净矿化速率在各培养阶段均随土壤水分含量的增加而逐渐增大,其中75%WHC(75%田间持水量)和75%WHC+U(75%田间持水量+尿素)处理的矿化作用最强。土壤质地从一定程度上对土壤的矿化产生影响,但其影响并不显著。外源氮添加能促进土壤氮矿化,其净氮矿化量和净矿化速率在各培养阶段均极显著(p0.01)高于未加氮处理,分别为未施氮处理的1.68~4.56倍,0.60~6.47倍。外源氮添加使土壤pH显著下降,55%WHC+U、65%WHC+U和75%WHC+U处理分别下降了0.57,0.66,0.72个pH单位,土壤有酸化趋势。土壤pH值与土壤氮素净矿化速率呈极显著线性相关,净矿化速率对pH变化贡献巨大。总之,土壤含水量增加和外源氮添加均促进了土壤氮矿化,增加了土壤矿质氮含量,同时外源氮添加也加速了土壤pH下降,土壤有酸化趋势。     

闽南农业流域土壤氮矿化作用初步研究

用原位培养法对五川流域内的香蕉地、菜地、香蕉地与菜地间作地、林地、甘蔗地土壤的氮矿化作用进行了研究,结果发现不同土地利用方式下土壤氮矿化速率平均为N0.11mgkg-1d-1,其中香蕉地土壤氮矿化最高可达N1.47mgkg-1d-1;土壤硝化速率平均为N0.27mgkg-1d-1,其中菜地下土壤硝化作用强度最高可达N0.69mgkg-1d-1。土壤矿化作用同土壤湿度、温度、C/N、土壤肥力存在明显的相关关系。不同土地利用方式下温度是土壤氮矿化最主要的影响因子。闽南流域土壤年矿化量平均为N240kghm-2,部分样地最高可达N850kghm-2,而年施肥量平均N650kghm-2。相比较而言,说明了土壤矿化是我国南方流域农业土壤氮素的重要来源。     

耕作方式对土壤不同粒径团聚体氮素矿化的影响

研究了常规耕作和垄作免耕两种耕作方式下紫色水稻土不同粒径团聚体中氮的矿化过程。结果表明,不同粒径团聚体氮素矿化强度具有显著差异:潜在矿化势(Np)的最高值均出现在2.0～0.25 mm大团聚体中,最低值在>2.0 mm的宏团聚体中;2.0～0.25 mm团聚体的潜在矿化速率(Vp)和实际矿化速率(Va)比其他团聚体高1.2～1.6倍。常规耕作和垄作免耕两种耕作方式下不同团聚体的净矿化率随时间的变化趋势相同;垄作免耕显著增加了氮素的净矿化量,以原土为例:垄作免耕处理Np比常规耕作处理高33.9%,Vp和Va分别比常规耕作处理高85.2%和52.0%。虽然垄作免耕可以显著促进土壤中氮素的矿化作用,但是耕作方式对不同粒径团聚体内的氮矿化动力学过程并无显著影响,表明耕作方式对不同大小团聚体中可矿化氮和微生物的分布影响较小。     

添加凋落物对杨树人工林土壤氮、磷矿化的影响初探

采用室内培养方法,在30℃和土壤含水量为田间持水量的70％的条件下研究杨树人工林的枯叶或枯枝、枯地被植物、杨树根系以及混合凋落物的添加对土壤氮和磷矿化的影响.结果表明:(1)培养42 d后,不同处理间的土壤有效磷含量存在一定差异,呈现枯叶+土＞枯地被植物+土＞混合凋落物+土＞根+土＞枯枝+土＞对照的趋势;(2)不同处理间的土壤铵态氮含量差异比较小;(3)各种处理的硝态氮含量占总无机氮的78％以上;(4)在培养初期,除添加枯枝处理外,添加其他凋落物处理的土壤硝态氮和总无机氮含量明显下降,后期逐渐升高;(5)土壤无机氮、磷含量及其矿化速率与土壤和凋落物的性质密切相关.     

不同土壤质地和含水率对炭基肥料氮素矿化的影响

为了探究土壤特性对炭基肥料氮素矿化的影响,采用室内培养和大田小区试验,分析了炭基肥在不同土壤质地(砂质壤土、粉砂质壤土、黏土)及含水率(80%、60%、40%田间最大持水量)条件下,氮素矿化动态变化特征。结果表明:在室内培养条件下,对于不同土壤质地,炭基肥在砂质壤土条件下矿化势最高,其次为黏土,最低的为粉砂质壤土;对于不同田间持水量,在粉砂质壤土条件下,炭基肥矿化势最高的为80%田间最大持水量(80%SMC),其次为60%SMC,最低的是40%SMC;在砂质壤土和黏土条件下,炭基肥的矿化势均表现为60%SMC> 80%SMC> 40%SMC。培养状态下粉砂质壤土、砂质壤土、黏土条件下最大氮素有效性分别是34.12%、56.31%、41.14%,而在大田条件下,炭基肥单季氮素最大矿化率在粉砂质壤土、砂质壤土、黏土3种土壤质地下分别是50.61%、32.27%、34.29%。     

长期不同化肥氮用量对设施菜地土壤氮素矿化和硝化作用的影响

为揭示长期施用不同化肥氮对设施菜地土壤供氮能力的影响,选取连续种植15年不同化肥氮用量下的设施菜地土壤,采用好气密闭培养法研究长期不同化肥氮用量对设施菜地土壤氮素矿化和硝化作用的影响.供试土壤为5个氮施用水平,分别为:不施化肥氮(CK),常规化肥氮(100％N),常规化肥氮上减氮20％(80％N)、40％(60％N)、...     

Mineralization of Propylene Glycol in Root Zone Soil

Propylene glycol is a common component on aircraft deicingfluids. Runoff from airports may contain high concentrations ofpropylene glycol, leading to a high biological oxygen demand(BOD) in the runoff. Root zone soils support a diverse microbialcommunity and have been shown to enhance biodegradation of numerous compounds. Root zone soils from several grasses andlegumes were tested for their ability to enhance mineralizationof propylene glycol. Propylene glycol (1000 ppm) was applied toroot zone soils incubated at either 22 or 7 °C underdarkened conditions. Root zone soils from legumes showed thehighest rate of mineralization, however, soils from variousgrasses did not show consistently different mineralization ratesfrom each other. Mineralization rates decreased 2.2 to 4.2-foldat the lower temperature; however, treatment soils stillmineralized propylene glycol faster than autoclaved controls.     

温度和水分对典型香型烟区植烟土壤氮素矿化的影响

为探究典型香型烟区植烟土壤氮素矿化特征及其与温度和水分的关系,采用室内培养试验研究了土壤温度(15、28、37℃)和土壤相对含水量(50%、65%、80%田间持水量)对云南大理、贵州毕节、河南许昌3个典型香型产区植烟土壤氮素矿化的影响。结果表明:不同地区植烟土壤矿质氮和矿化速率变化规律与温度和水分密切相关。3个产区植烟土壤的矿质氮含量和矿化速率均随着温度的升高而升高,在同一温度条件下,以土壤有机质含量较高的云南大理土壤矿化量较大,有机质含量较低的河南许昌土壤矿化量较小。不同地区植烟土壤含水量与氮素矿化的关系不尽相同,土壤相对黏重的贵州毕节土壤以50%田间持水量处理土壤氮素矿化量和矿化速率最大,以80%田间持水量处理最不利于氮素矿化;而质地相对较轻的河南许昌土壤和云南大理土壤均为在65%田间持水量条件下最有利于氮素矿化,以50%田间持水量处理氮素矿化量较小。基于一级动力学方程的模拟,3个植烟土壤的潜在矿化氮库(N0)都随温度的增加而提高,总体以28～37℃的培养温度较为适宜,低于15℃不利于土壤有机氮的矿化,3个植烟土壤的N0以云南大理最高,河南许昌最低;土壤矿化速率常数(K)以云南大理最大。土壤相对含水量也对N0有一定影响,且土壤温度和含水量对不同土壤氮素矿化量和矿化速率均存在显著的互作影响,合理调控土壤温度和土壤相对含水量,可以有效调节不同生态烟区土壤氮素矿化动态变化。     

外源氮输入对土壤有机碳矿化和凋落物分解的影响

目前,由人类活动造成的陆地生态系统氮输入量已经远远超过了其自身的生物固氮,外源氮输入的增多已经并将继续对土壤有机碳矿化和凋落物分解产生影响。本文分析了国内外有关氮输入增多对土壤有机碳矿化和凋落物分解的影响及其机理:由于研究点环境状况不同,凋落物性质的差异和分解阶段的不同等原因,氮输入对土壤有机碳矿化的结果主要表现为抑制或促进作用;对凋落物分解的影响表现为促进、无影响和抑制三种效果,有关其作用机理还有待进一步深入研究。着重指出对于作为大气CO2"汇"的沼泽湿地,氮输入的增多能够对其碳"汇"功能产生影响,因此进行氮输入对湿地土壤有机碳矿化和凋落物分解方面的研究,对于探讨湿地碳循环对外源氮输入的响应及其机理非常重要。     

水分条件对不同类型土壤氮矿化及酶活性的影响

针对凉攀烟区立体气候特征明显，干湿分明特征，从水分变化角度研究植烟土壤氮素矿化及其酶活变化特征，为合理调控土壤氮素供应提供科学依据。以凉攀烟区土壤为研究对象，通过室内培养法研究了不同水分条件培养下（60%田间持水量（60%WHC），淹水状态（FS）），土壤（红壤、紫色土）氮矿化动力学及酶活性特征。结果表明，（1）与60%WHC相比，FS培养条件提高了土壤NH4+-N含量，且培养期内紫色土NH4+-N平均含量较红壤增加6.0%~9.0%； 60%WHC培养下土壤NO3--N含量明显高于FS，且培养期内红壤NO3--N平均含量（40.7~64.1 mg/kg）高于紫色土（38.0~56.4 mg/kg）；（2）FS培养提高了土壤氨化速率，紫色土平均氨化速率均高于红壤，60%WHC培养提高了土壤硝化速率，且红壤平均硝化速率高于紫色土；（3）培养期内，60%WHC培养下土壤无机氮累积矿化量明显高于FS，红壤氮矿化潜力强于紫色土，其中红壤在60%WHC培养下的土壤无机氮累积矿化量最大（42.12~394.06 mg/kg），其次是同一水分条件培养下的紫色土；（4）土壤脲酶、蛋白酶和亚硝酸还原酶的活性与土壤无机氮矿化累积量存在显著的相关性，红壤的脲酶活性强于紫色土，尤其是在60%WHC培养的效果更为显著；紫色土的蛋白酶活性和亚硝酸还原酶活性高于红壤，尤其是在FS培养下的效果显著。总体上，凉攀烟区红壤氮矿化潜力强于紫色土，尤其是在60%WHC条件下，在推荐氮肥施用量时，不仅要考虑不同土壤类型，而且还应该注意土壤水分状况的调控，防止烤烟生长后期氮素供应能力过强，影响烟叶成熟落黄和香气物质形成。     

有机肥施用对植烟土壤氮素矿化及土壤酶和微生物群落的影响

为探索不同有机肥对植烟土壤氮素矿化及土壤微生态的影响。在等氮(100 mg/kg)投入和30℃条件下对施入不同有机肥(植物源有机肥、芝麻饼肥、生物质炭有机肥)的土壤进行室内培养，分析不同时期土壤NO3–-N和NH4+-N含量、土壤酶活性及细菌群落多样性的变化。结果表明：施用不同有机肥均可提高土壤矿质氮含量，在培养前期以饼肥矿化量最高，矿化速率最快，而后期为生物质炭有机肥处理的氮素矿化量、矿化速率高于其他处理；施用生物质炭有机肥、植物源有机肥均可显著提高土壤脲酶、硝酸还原酶活性，芝麻饼肥对蛋白酶、蔗糖酶活性有显著的提升作用；相较不施有机肥处理，添加不同有机肥的土壤细菌多样性明显提升。优势菌门为变形菌门、酸杆菌门、拟杆菌门、浮霉菌门，优势菌属为Sphingomonas、RB41,Sphingomonas在不施有机肥处理中最高，RB41在生物质炭有机肥处理中最高。Sphingomonas与蔗糖酶活性呈正相关关系，与脲酶、硝酸还原酶均呈负相关关系；PCA分析显示，生物质炭有机肥处理的细菌群落结构与其他处理相比差异较大。施用芝麻饼肥有利于促进早期氮素矿化，提高矿化量，而生物质炭有机肥后期矿化量较...     

Significance of Enzyme Activities in Soil Nitrogen Mineralization

This study was undertaken to assess the relationship between nitrogen (N) mineralization in soils treated with eight lime application rates, with four field replications, and the activities of six amidohydrolases involved in N cycling and four glycosidases involved in carbon (C) cycling in soils. Nitrogen mineralization was studied at 20 or 30 °C for 20 weeks, and with the exception of N‐aceyl‐β‐D‐glucosaminidase (NAGase; EC 3.2.1.30) activity, which was assayed at both temperatures, the enzyme activities were assayed at 30 °C at their optimal pH values. Results showed that among the eight enzyme activities studied, NAGase activity was the most significantly correlated with the cumulative amounts of N mineralized in 32 soil samples at 20 °C (r = 0.87***) and at 30 °C (r = 0.95***). The cumulative amounts of N mineralized at 30 °C were also significantly correlated with arylamidase and L‐aspartase activities, with r values of 0.61*** and 0.52**, respectively. Because NAGase activity is involved in both N and C cycling, the cumulative amounts of N mineralized at 30 °C were also significantly correlated with the activities of β‐glucosidase (r = 0.80***) and β‐galactosidase (r = 0.58***). Activities of other N enzymes that were significantly correlated with the cumulative amounts of N mineralized at 30 °C in 20 weeks were those of L‐asparaginase (r = 0.61***), urease (r = 0.57***), amidase (r = 0.54**), and L‐glutaminase (r = 0.41*). It seems that the activity of NAGase can be used as an index of N mineralization in soils.     

Sensitivity of Nitrogen Mineralization Indicators to Crop and Soil Management

Abstract

Soil nitrogen (N) mineralization indicators are useful only if they are sensitive to management practices. The precision of measurement and the sensitivity of the following indicators to crop sequence, tillage, and liming effects were compared: (i) mineral N production during a 24‐day incubation under aerobic conditions, (ii) ammonium (NH₄)‐N production under waterlogged conditions, (iii and iv) hot potassium chloride (KCl)–extractable and hydrolyzable NH₄‐N (the latter obtained by subtracting initial NH₄‐N from extracted NH₄‐N), and (v) protease activity. The coefficients of variation decreased in this order: protease activity>KCl‐hydrolyzable NH₄‐N>aerobic incubation>KCl‐extractable NH₄‐N=anaerobic incubation. Most of the test results obtained using the indicators were correlated with each other. Mineralizable N measured by aerobic and anaerobic incubation was sensitive to tillage, liming, and crop sequences, especially when using soil 5‐cm deep. Hot KCl‐extractable NH₄‐N was influenced by tillage but not liming, and less sensitive than the incubation procedures to crop sequence. The protease assay produced no significant test. It was concluded that anaerobic incubation can provide a relatively sensitive assessment of management effects on soil mineralizable N.     

Soil Moisture and Temperature Effects on Nitrogen Mineralization in a High Tunnel Farming System

ABSTRACT

Effects of temperature and moisture on nitrogen (N) mineralization from organic amendments in high tunnel farming systems are rarely studied to assist N fertilizer management for high N-demand crops with short cycles. In this study, soils from a new high tunnel site were incubated at four temperatures (2, 10, 20, & 30°C) and five gravimetric water contents (15, 20, 25, 30, & 35%) with and without a dried and ground alfalfa amendment. Net N mineralization was determined by measuring NH₄⁺-N and NO₃^–-N contents periodically over 84 days. Significant main effects of temperature and moisture were found (p < .0001) and tendencies of a significance of alfalfa amendment (p = .0855) and interaction between amendment and temperature (p = .0842) were observed. Only a significant increase of the net mineralized N at 30ºC in amended soil was observed compared to unamended soil (p = .0043). Estimated from the first-order exponential model, maximum potential mineralized N was 1.2 times greater while mineralization rate was up to 2.1 times greater in amended soil compare to un-amended soil. Q₁₀ estimated from the Arrhenius model ranged from 1.62 to 2.04 in the amended soil and 1.66 to1.85 in the un-amended soil. The average optimal soil water content for maximum N mineralization estimated from the Gaussian function model was 33.8% in amended soil and 35.9% in un-amended soil. The results from this study can be used to suggest soil moisture and temperature management strategies to control N availability in high tunnel systems.     

长期施肥对水稻土碳氮矿化与团聚体稳定性的影响

水稻土有机碳、氮矿化过程对水稻土质量和作物养分吸收具有重要的作用,但是它们对施肥措施的响应及其与土壤结构之间的关系尚不清楚。本研究基于红壤性水稻土长期施肥定位试验,分析了不施肥(CK)、施用常量化肥(NPK)、2倍化肥(NPK2)和常量化肥配施有机肥(NPKOM)等处理下水稻土碳氮矿化特征,并研究了其与土壤团聚体稳定性的关系。结果表明NPKOM处理显著提高了土壤有机碳和全氮含量(P0.05),而单施化肥处理(NPK2和NPK)则同CK处理没有显著差异。土壤有机碳矿化速率、累积矿化量和矿化率均为NPKOMNPK2NPKCK处理,其中NPKOM处理显著高于其他处理(P0.05),而后3个处理间没有显著差异。土壤氮矿化速率、累积矿化量和矿化率同土壤碳矿化的规律一致,NPKOM、NPK2和NPK处理累积矿化氮量较CK处理分别提高110.0%、29.4%和8.8%,矿化率分别提高110.8%、25.6%和13.0%。单施化肥处理(NPK和NPK2)的平均质量直径(MWD)分别降低了17.1%和15.5%,而NPKOM处理则增加了19.4%。相关分析表明,土壤碳氮矿化主要取决于土壤有机碳氮含量,而与土壤团聚体水稳定性无直接关系。在今后研究中,应重点分析土壤孔隙结构与有机碳氮周转的关系。     

模拟搅浆对水稻土结构和有机氮矿化的影响

搅浆(Puddling)是传统水稻种植过程中的重要环节,搅浆会改变土壤结构,进而影响氮转化过程。通过室内模拟试验,设置不搅动(CK)、低强度搅动(LIS)和高强度搅动(HIS)三个处理,研究搅浆引起的土壤结构变化,及其对土壤有机氮矿化的影响。首先利用湿筛法测定不同处理团聚体分布及稳定性,采用CT扫描和图像分析方法研究不同处理土壤孔隙结构,并通过室内培养法测定土壤有机氮矿化量,进一步分析土壤结构与有机氮矿化之间的关系。结果显示,与CK相比,LIS和HIS两处理中大于1 mm的水稳性团聚体含量和平均重量直径(MWD)均显著降低,LIS和HIS处理间无显著差异。CK、LIS和HIS的土壤孔隙度分别为3.3%、3.2%和3.3%,各处理间无显著差异;但三个处理的土壤孔隙形态有明显差异,CK大孔隙分布较多且连通性好,LIS和HIS处理孔隙多为球状孔隙,连通性较差。矿化培养第一周,LIS和HIS处理矿化量均快速增加,高于CK处理;但是培养2周后CK矿化氮高于搅动处理,培养试验结束时(4周)CK累积矿化氮量(N28)和氮矿化潜势(N0)显著高于LIS和HIS处理,说明搅拌降低了有机氮的累积矿化量。相关分析表明,土壤有机氮矿化与粒径大于0.25 mm的团聚体含量和当量直径为30～100μm的孔隙数量具有显著正相关关系,其内在机制尚待进一步研究。     

土地利用方式对红壤氮素矿化和硝化作用的影响

研究在我国亚热带红壤地区采集林地、竹林、茶园和旱地农田4种利用方式的土壤样品,测定了氮素净矿化和净硝化以及N_2O排放速率,定量了氨氧化细菌(AOB)和氨氧化古菌(AOA),以期阐明土地利用方式对红壤氮素矿化和硝化作用的影响。结果表明,不同利用方式红壤AOA基因拷贝数在6.20×10~6到6.58×10~6copies g~(-1)土;AOB基因拷贝数在4.18×10~6到7.41×10~6copies g~(-1)土,AOA和AOB丰度的最大值均出现在旱地红壤。旱地红壤0～7天和0～14天的氮素净矿化速率分别为3.46和1.62 mg kg~(-1),均显著高于其他利用方式。氮素净矿化速率与土壤pH值呈显著的正相关关系(P0.05),与C/N呈显著的负相关关系(P0.05),说明土壤pH和C/N是影响不同利用方式红壤氮素净矿化速率的主要因子。旱地红壤0～7天和0～14天的净硝化速率分别为5.33和3.06 mg kg~(-1),也均显著高于其他利用方式。净硝化速率与铵态氮(NH_4~+-N)含量(P0.01)、pH(P0.05)和AOB(P0.01)均呈显著的正相关关系,表明土壤p H和可利用NH_4~+-N含量是影响红壤净硝化速率的重要因素,高土壤pH和NH_4~+-N含量有利于AOB的生长和活性,从而明显增加净硝化速率。然而,不同利用方式红壤的N_2O排放速率却没有显著的差异,说明利用方式似乎不影响土壤N_2O排放,这与净硝化速率变化规律相矛盾。可能的原因是,除了硝化作用外,好氧培养条件下还存在其他重要的N_2O产生途径,将来的研究中需要关注不同利用方式红壤N_2O产生途径,以阐明红壤N_2O排放机制。