Chloride interference in total nitrogen analysis by the Kjeldahl method

Abstract

Very low recovery of NH₄+‐N was observed in total N determination of (NH₄)₂SO₄ in KC1 solutions by a semimicro Kjeldahl method using permanganate and reduced iron to recover NO₃‐ and NO₂‐, whereas complete recovery was obtained in analysis of NH₄+‐N in water, and of NO₃ ^?‐N or NO₂ ^?‐N in either water or KC1 solutions. The loss of NH₄ ⁺‐N observed with KC1 was attributed to the formation of NCl₃ upon reaction of NH₄ ⁺ with Cl₂ generated during oxidation of Cl^? by MnO₄ ^?. This difficulty is avoided by using K₂SO₄ instead of KC1 for extraction of inorganic N from soil. Complete recovery was obtained by adding ¹⁵N‐labeled NH₄+, NO₃‐, or NO₂‐ to 0.5 M K₂SO₄ soil extracts, and total ¹⁵N analyses of the labeled extracts were in good agreement with values calculated from the additions of ¹⁵N and the total N contents of the soil extracts.     

半自动定氮仪测定肥料中总氮含量的研究

通过对肥料中氮形态的定性鉴定,选择适合的前处理方式,将其它形态的氮转化为铵态氮,用半自动定氮仪蒸馏测定总氮含量。通过与国家标准方法比对,表明该方法具有准确、快速、节省试剂、适合批量测定等特点,是肥料中氮含量测定的好方法。     

Determination of total dissolved nitrogen by persulfate oxidation

The alkaline persulfate oxidation, converting all N into nitrate, is an easy and rapid method for determining total dissolved nitrogen. We found indications that atmospheric N is trapped during the oxidation step, which can be impeded by: (1) using always the same type of autoclave bottle and a constant sample volume; (2) minimising the remaining headspace in the bottle; (3) closing the bottle caps tightly for autoclavation; and (4) determining blanks for each test series.     

不同品种辣木全氮的动态变化特征研究

为了解不同品种辣木氮的动态变化规律,对西双版纳不同树龄的多油辣木、狭瓣辣木和‘PKM1’辣木叶、茎、枝中全氮含量及氮的生物累积量年动态变化特征进行比较研究。结果表明,辣木氮含量及氮生物累积量随品种、树龄、时间而变化。辣木全氮含量呈现:叶茎枝,14年树龄3年树龄,随时间变化逐渐降低。叶中全氮含量呈现:多油辣木‘PKM1’辣木狭瓣辣木;茎中全氮含量呈现:‘PKM1’辣木和狭瓣辣木高于多油辣木;枝中辣木氮含量受品种、树龄的影响而呈现不同差异。辣木全氮累积量呈现:枝叶茎,狭瓣辣木和多油辣木最高,‘PKM1’辣木最低。     

快速测定化肥中的总氮方法

应用美国力可公司生产的煤炭碳、氢、氮分析仪测定化肥中总氮的含量 ,通过炉温、样品量、放大器增益的选择 ,积分时间等的对比 ,确定了以CHN— 1 0 0 0分析仪测定化肥总氮的检测方法 ,本方法测定速度快、精密度高、准确度好 .氮的相对标准偏差小于 0 5%     

基于全株生物量和全株氮浓度的马铃薯氮临界浓度稀释模型的构建及验证

  【目的】  临界氮浓度稀释曲线的构建是作物氮素营养诊断的基础,然而其曲线参数可能受品种等因素影响。本研究的主要目的是构建滴灌条件下常见马铃薯品种临界氮浓度稀释曲线模型,并利用相应的氮素营养指数进行马铃薯氮素营养诊断。  【方法】  于2014—2016年分别进行了滴灌条件下3个马铃薯品种、不同施氮量的田间试验。在马铃薯苗期、块茎形成期、块茎膨大期、淀粉积累期和收获期5个关键时期,进行地上部茎叶和地下部块茎取样,分别测定了生物量和氮浓度,根据公式计算出马铃薯全株生物量和全株氮浓度。根据全株生物量和全株氮浓度建立临界氮浓度稀释模型和相应的氮素营养指数。  【结果】  马铃薯地上部生物量和地上部氮浓度以及全株生物量和全株氮浓度都是随着生育时期的推进呈现出负幂函数关系,基于地上部生物量和地上部氮浓度建立的临界氮浓度稀释曲线决定系数平均为0.52,而以马铃薯全株生物量和全株氮浓度建立临界氮浓度稀释曲线决定系数平均为0.94,较前者提高了80%。以马铃薯全株生物量和全株氮浓度建立临界氮浓度稀释模型更为合理,且受品种影响较小,克新1号、夏坡地和荷兰14用同一个临界氮浓度稀释曲线的决定系数均达到0.95,表明构建的氮素营养模型可以进行不同品种的马铃薯氮素营养诊断。  【结论】  相对于传统籽粒型作物基于地上部生物量和地上部氮浓度建立临界氮浓度稀释模型,基于全株生物量和全株氮浓度建立的临界氮浓度稀释模型适用于不同品种马铃薯的营养诊断。在内蒙古滴灌生产条件下,马铃薯临界氮浓度稀释模型为Nc = 4.57W–0.41,基于该模型计算的马铃薯克新1号合理施氮量为N 170～180 kg/hm2、夏坡地合理施氮量为 190～200 kg/hm2、荷兰14合理施氮量为 215～225 kg/hm2。这些计算结果与试验结果的吻合度达到了0.95。     

滴灌施肥对农田土壤氮素利用和流失的影响

通过2年在果园和蔬菜田的生产试验及田问氮素流失监测,对比研究常规施肥管理和精确滴灌施肥技术在作物产量、肥料消耗量和农田氮素流失负荷等方面的差异,分析不同施肥方式对农田土壤氮素利用和流失的影响.结果表明:滴灌施肥技术把定量的溶解态肥料直接输送到作物根部,提高了肥料利用效率,农作物产量与常规产量基本持平甚至略有提高,而氮肥消耗量和氮素流失负荷则显著降低.与常规施肥管理方式相比,2006年梨、大豆和玉米的单位产量氮肥消耗量分别降低10.8、11.8和8.9 g/kg,削减率分别为22.8%、26.6%和30.8%;单位产量总氮流失量也分别削减45.2%、14.5%和26.3%.2007年梨、西瓜和玉米的单位产量氮肥消耗量分别降低11.1、8.1和5.0 g/kg,削减率分别达到29.7%、65.8%和21.5%;单位产量总氮流失量分别削减56.4%、49.7%和51.8%.     

High-throughput analysis of total nitrogen content that replaces the classic Kjeldahl method

A high-throughput method for determination of total nitrogen content has been developed. The method involves decomposition of samples, followed by trapping and quantitative colorimetric determination of the resulting ammonia. The present method is rapid, facile, and economical. Thus, it can replace the classic Kjeldahl method through its higher efficiency for determining multiple samples. Compared to the classic method, the present method is economical and environmentally friendly. Based on the present method, a novel reactor was constructed to realize routine high-throughput analyses of multiple samples such as those found for pharmaceutical materials, foods, and/or excrements.     

A field method for the determination of total nitrogen in plant tissue

Abstract

While studying sward quality in Kenya, East Africa, we established a field laboratory for the determination of total nitrogen. Using Kjeldahl digestion procedures and an indophenol colorimetric method, we successfully analyzed over 900 plant and fecal samples while living in a tent camp. Variation from one digestion to the next was corrected for by using a grass standard with each digestion. Independent tests by other laboratories verified the accuracy of our methods.     

Contribution of dissolved organic nitrogen deposition to total dissolved nitrogen deposition under intensive agricultural activities

For elucidating the atmospheric deposition contribution of dissolved organic nitrogen (DON) to the total dissolved nitrogen (TDN) deposition rate, dissolved inorganic nitrogen (DIN: NH₄ ⁺ + NO₃ ^–) and DON deposition rates were annually and monthly estimated during 4 and half-yr monitoring period in an experimental multi-farm under intensive agricultural activities of N fertilizer use and animal husbandry in Central Japan. Annual NH₄ ⁺, DON and NO₃ ^– deposition rates in bulk and wet deposition data accounted for 48%, 32% and 20% of TDN deposition, respectively, which indicated that this area is strongly affected by the intensive agricultural activities. The DIN and DON deposition rates were respectively estimated at 21.6 and 10.1 kg N ha^?1 yr^?1, which ranked high in a worldwide regional data set. Consequently, this area has been exposed to a large amount of N deposition including DON with N fertilizer input. The difference between bulk and wet deposition rates (NH₄ ⁺ and DON) is one of important factors controlling the N deposition in this area. Monthly DON deposition showed positive correlations with DIN and NH₄ ⁺ deposition rates, respectively, with a significant linear regression curve. The linear regression curve of our monthly data (n = 127) indicates the same trend as the worldwide annual data set (n = 31).     

Use of ammonia electrode for total nitrogen determination in plants

Abstract

An ammonia electrode was evaluated as a means of determining ammonium concentration in semi‐micro Kjeldahl digests of plant samples. Results of the ammonia electrode determination agreed closely with distillation and titration results. Advantages of the electrode method include speed, precision, increased safety, simplicity and the fact that only a small aliquot of the digest is used.     

黄土高原典型土壤全氮和微生物氮剖面分布特征研究

为阐明黄土高原典型土壤全氮和微生物氮含量随土壤类型、土层和土地利用方式变化规律,研究了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(杨陵)等典型土壤的全氮和微生物氮含量的变化特征。结果表明,不同土壤类型、不同土层全氮和微生物氮含量存在显著差异。从南到北,全氮和微生物氮含量显著下降(P0.05)。对同一土壤类型,全氮和微生物氮含量在060.cm随土层深度增加下降很明显,60120.cm有轻微下降,120.cm以下低而稳定。微生物氮含量随土壤类型的变化趋势与全氮完全相同,其与土壤全氮、有机碳及微生物碳含量均存在极显著正相关关系(P0.01)。土壤微生物氮与全氮比值变化在0.42%9～.44%之间。虽然土地利用对土壤全氮和C/N比影响不显著,但却显著影响微生物氮含量和微生物氮与全氮的比值;与农田土壤相比,草地土壤微生物氮含量和微生物氮与全氮比值均明显增加。这一结果说明微生物氮含量和微生物氮与全氮比值更能有效、快速地反映土壤质量的变化。     

Use of an AutoAnalyzer for total nitrogen determination in plants

Abstract

An AutoAnalyzer was evaluated as a means of determining ammonium concentration in semi‐micro Kjeldahl digests of plant tissue. Results of the AutoAnalyzer determination agree closely with distillation‐titration results. Advantages of the AutoAnalyzer method include speed, precision, and release of labor. Only a small aliquot of each digest is utilized.     

长期施肥下潮土全氮、碱解氮含量与氮素投入水平关系

通过长期肥料定位试验,对不同施肥处理下潮土全氮和碱解氮含量演变特征及其与氮素投入水平的关系进行研究。结果表明,不施氮肥处理,土壤全氮和碱解氮含量基本保持平衡或者缓慢增加;长期施用化学氮肥处理,土壤全氮和碱解氮含量均有所增加;施用有机肥和秸秆还田处理,土壤全氮和碱解氮含量均显著提高。单施化学氮肥处理每投入氮素1 kg/hm2,土壤全氮含量增加0.017 mg/kg;而氮磷钾化肥配施有机肥和氮磷钾化肥并秸秆还田处理每投入氮素1 kg/hm2,土壤全氮含量分别增加0.049和0.035 mg/kg。施氮磷钾处理每投入氮素1 kg/hm2,土壤碱解氮含量增加0.001 mg/kg;而化肥配施有机肥或玉米秸秆处理每投入氮素1 kg/hm2,土壤碱解氮含量均增加0.004和0.004 mg/kg。总的来说,施用化学氮肥、有机肥配施化肥及秸秆还田处理增加氮素投入量均可以提高土壤全氮及碱解氮含量,且有机肥配施化肥及秸秆还田处理优于单施化肥。综上所述,增施有机肥及秸秆还田对于提升土壤肥力及实现农业可持续发展具有深远意义。     

氮素形态对半夏生长及生物碱和总有机酸累积的影响

研究氮素形态对半夏光合特性、相关酶活性、总生物碱及总有机酸累积的影响,为半夏氮肥的合理施用提供依据。采用无土栽培方法栽培半夏,测定同一氮素水平不同氮素形态处理下,半夏叶片叶绿素含量、相关光合参数、硝酸还原酶（NR）活性、硝态氮含量、块茎中总生物碱及总有机酸含量。结果表明:半夏叶片光合色素含量随铵硝比增大呈先升后降趋势;铵硝比为75∶25时,叶绿素a和类胡萝卜素含量最高;铵硝比为25∶75,叶绿素b含量最高,同时,净光合速率、气孔导度和蒸腾速率达最大值;随着NO3--N比例降低,NR活性整体呈现下降趋势;块茎总生物碱含量,全硝营养下含量最高,随着NO3--N比例降低,呈现降低趋势;而随着NH4+-N比例增加,半夏块茎中总有机酸呈现上升的趋势。结论:铵态氮、硝态氮复合施用有利于半夏的生长,较高硝态氮比例有利于总生物碱的积累,较高铵态氮比例有利于总有机酸的累积。     

黑土土壤中全氮含量的高光谱预测分析

为实现快速、准确估测土壤氮素含量水平,推动土壤信息化管理进程,该研究利用ASD2500高光谱仪在室内条件下测定了风干土壤样品的可见—近红外光谱。结果表明,通过不同的变换,光谱反射率对数的一阶导数与土壤全氮含量相关性得到增强,以400～600 nm波段范围内相关性最好。该文确定了以反射率对数的一阶导数光谱预测黑土全氮（TN）含量的最佳回归模型,模型所用的波段为可见光波段的556 nm、近红外的1 642和2 491 nm。同时,也确定了利用由可见光波段550和450 nm组成的归一化光谱指数预测黑土TN含量的最佳预测模型。模型通过验证达到较好的效果：利用反射率对数的一阶导数、归一化光谱指数对土壤TN的预测R2分别为0.863、0.829,均方根误差RMSE分别为0.122、0.152。     

复合肥料中总氮含量测定的能力验证研究

为提升北京市周边地区复合肥料生产企业产品质量,提高企业出厂检验能力,开展生产企业测定复合肥料中总氮含量的能力验证研究.能力验证样品符合均匀性和稳定性要求,总氮含量测定结果采用频率分布统计和稳健Z比分数统计方法进行分析研究.研究结果表明,18家参与能力验证单位的数据集中分布在中位值17.12附近,仅有低频数偏离,本次测定...     

松花江流域非点源氮磷负荷及其差异特征

为了研究松花江流域非点源氮磷污染负荷和差异,为水环境管理提供参考,该文运用数字高程模型（DEM）、2008年县级统计年鉴和土地利用等数据,基于遥感（RS）和地理信息系统（GIS）技术,利用输出系数模型（ECM）,对松花江流域非点源污染进行了空间模拟和负荷估算,并对流域内非点源污染差异特征进行了分析。结果表明,2008年松花江流域的总氮（TN）负荷为112.99×104 t,总磷（TP）负荷为4.05×104 t。其中,嫩江子流域TN和TP负荷最高,分别为52.08×104 t和1.79×104 t,分别占总量的46.09%和44.14%;第二松花江流域TN和TP负荷强度最高,TN负荷强度2.96 t/(km2·a),TP负荷强度 0.11 t/(km2·a)。从非点源成因角度分析,人为原因产生的非点源TN和TP负荷分别为95.92×104 t和3.40×104 t,分别占总量的83.90%和83.94%。人为原因是松花江流域非点源TN和TP产生的关键,天然原因也不容忽视。研究结果为总体上了解松花江流域非点源污染和水环境管理提供参考。     

流动分析仪同时快速测定植物全氮、全磷含量的方法改进

为了充分发挥流动分析仪的检测优势,准确高效地同时测定植物全氮、全磷含量,对现有方法提出改进,并将改进方法与传统方法的测定结果进行比较分析,探讨流动分析仪同时测定植物全氮、全磷含量改进方法的可行性.结果表明,经t检验改进方法与传统的扩散法所测全氮含量无显著性差异(P＞0.05),改进方法与传统的钼锑抗比色法所测全磷含量无...