大多数土壤的有机磷(Po)占全磷30%~65%,矿化后可被植物直接利用,成为生态系统生物有效磷重要来源。准确测定Po形态组成及矿化速率是科学利用土壤Po库的基础。本文目的是对目前常见土壤Po形态组成和矿化速率测定技术的优缺点、适用范围...大多数土壤的有机磷(Po)占全磷30%~65%,矿化后可被植物直接利用,成为生态系统生物有效磷重要来源。准确测定Po形态组成及矿化速率是科学利用土壤Po库的基础。本文目的是对目前常见土壤Po形态组成和矿化速率测定技术的优缺点、适用范围进行总结分析,为研究人员选择合适测定技术提供依据。搜集并分析近20年来中国知网和Web of Science数据库中92篇关于Po形态组成与矿化速率方法研究论文。介绍了3种常用Po形态测定技术(连续分级法、酶水解法和核磁共振法)和近年来兴起的3种Po矿化速率测定技术(同位素稀释技术、连续观测-差减法和模型法)的基本原理,分析了几种技术适用范围、主要优缺点和互补性。尽管目前仍无针对土壤Po形态组成和矿化速率“最佳”测定方法,但是,研究人员可根据待测土壤理化性质和实验目的选择“合适”的测定技术。提出未来应在酶水解技术标准化、^(13)C和^(31)P核磁共振技术联用、发展包含植物因素Po矿化速率测定技术、联用形态和矿化速率测定技术等方面开展深入研究。展开更多
【目的】通过大豆盆栽试验,研究了秸秆生物炭与磷肥添加对红壤团聚体稳定性、磷组分分布与植物磷吸收的影响。【方法】试验包括6个处理:P0(不施磷和生物炭)、P30(30 kg P hm^(−2),不施生物炭)、P90(90 kg P hm^(−2),不施生物炭)、BP0(...【目的】通过大豆盆栽试验,研究了秸秆生物炭与磷肥添加对红壤团聚体稳定性、磷组分分布与植物磷吸收的影响。【方法】试验包括6个处理:P0(不施磷和生物炭)、P30(30 kg P hm^(−2),不施生物炭)、P90(90 kg P hm^(−2),不施生物炭)、BP0(不施磷,单施4%生物炭)、BP30(30 kg P hm^(−2),施4%生物炭)和BP90(90 kg P hm^(−2),施4%生物炭)。采用湿筛法分离得到粗大团聚体(>2 mm)、细大团聚体(0.25~2 mm)和微团聚体(<0.25 mm)并用连续浸提分级测定了不同团聚体中磷组分分布特征。【结果】①与P0和P30相比,BP0和BP30处理显著促进粗大团聚体形成与稳定,同时促进大豆生长与磷吸收,且BP30处理增幅最大。②与不施生物炭相比,不同磷水平下添加生物炭均显著降低粗大团聚体全磷、总有机磷、NH4F-Po和NaOH-I-Po含量,同时增加细大团聚体HCl-P_(i)和NaOH-II-P_(i)含量与微团聚体总无机磷、HCl-P_(i)和NaOH-II-P_(i)含量。③植株磷吸收与粗大团聚体总有机磷、NaOH-I-Po和NaOH-II-Po显著负相关,但与微团聚体和细大团聚体NH4Cl-P_(i)、HCl-P_(i)和NaOH-II-P_(i)显著正相关。【结论】生物炭与低量磷肥配施可有效改善红壤团聚体结构与稳定性,同时促进大团聚体有机磷的活化与微团聚体无机磷的固持,保障作物磷素供应。展开更多
In this paper we consider a discrete fractional boundary value problem(FBVP for short). We provide a delicate analysis for the property of Green’s function. Our analysis motivates the study of discrete fractional bou...In this paper we consider a discrete fractional boundary value problem(FBVP for short). We provide a delicate analysis for the property of Green’s function. Our analysis motivates the study of discrete fractional boundary value problems with fractional boundary conditions. As an application, we give conditions under which such problems admit at least one positive solution. Our results extend the results presented in [4].展开更多
The concentration and components of manure phosphorus(P)are key factors determining potential P bioavailability and runoff.The distribution of P forms in swine,poultry and cattle manures collected from intensive and e...The concentration and components of manure phosphorus(P)are key factors determining potential P bioavailability and runoff.The distribution of P forms in swine,poultry and cattle manures collected from intensive and extensive production systems in several areas of China was investigated with sequential fractionation and a simplified two-step(NaHCO3-NaOH/EDTA)procedures.The mean total P concentration,determined by the sequential fractionation procedure of intensive swine,poultry and cattle manure,expressed as g·kg–1,was 14.9,13.4 and 5.8 g·kg–1,respectively,and 4.4 g·kg–1 in extensive cattle manure.In intensive swine,poultry and cattle manure about 73%,74%and 79%of total P,respectively,was bioavailable(i.e.,P extracted by H2O and NaHCO3)and 78%in extensive cattle manure.The results indicated the relative environmental risk,from high to low,of swine,poultry and cattle manure.There is considerable regional variation in animal manure P across China,which needs to be considered when developing manure management strategies.展开更多
In this article, we discuss the existence and uniqueness of solutions for a coupled two-parameter system of sequential fractional integro-differential equations supplemented with nonlocal integro-multipoint boundary c...In this article, we discuss the existence and uniqueness of solutions for a coupled two-parameter system of sequential fractional integro-differential equations supplemented with nonlocal integro-multipoint boundary conditions. The standard tools of the fixed-point theory are employed to obtain the main results. We emphasize that our results are not only new in the given configuration, but also correspond to several new special cases for specific values of the parameters involved in the problem at hand.展开更多
文摘农田生态系统中土壤磷形态转化,影响土壤磷对作物的有效供应。土壤磷分为无机磷和有机磷两大部分。化学连续提取法(chemical sequential fractionation,CSF)研究土壤磷形态分级,采用不同的化学提取剂,分级提取土壤中组成或分解能力接近的有机无机含磷化合物,是目前表征土壤磷素形态的重要方法。但该方法虽历经改进,仍难以确切反映土壤磷的实际组成,提取的不同磷形态间存在重叠,有机磷和无机磷组分分级存在一定的误差;不同分级磷组分对作物的有效性,需谨慎评估。核磁共振波谱技术(nuclear magnetic resonance,NMR)根据核磁共振波谱图上共振峰的位置、强度和精细结构来研究土壤中含磷化合物的分子结构。液相31PNMR可以同吋检测出土壤中多种磷组分,如正磷酸盐、磷酸单酯、磷酸二酯、膦酸脂、焦磷酸盐和多聚磷酸盐,识别土壤提取物磷形态,可将有机磷与无机磷分开。本文综述了应用31P-NMR技术研究土壤磷形态组分的一些进展,总结了样品制备过程、NMR测试参数及在土壤磷形态转化研究中的应用。二维31P-NMR技术发展为鉴定分析土壤中更多种类的含磷化合物提供了契机。
文摘大多数土壤的有机磷(Po)占全磷30%~65%,矿化后可被植物直接利用,成为生态系统生物有效磷重要来源。准确测定Po形态组成及矿化速率是科学利用土壤Po库的基础。本文目的是对目前常见土壤Po形态组成和矿化速率测定技术的优缺点、适用范围进行总结分析,为研究人员选择合适测定技术提供依据。搜集并分析近20年来中国知网和Web of Science数据库中92篇关于Po形态组成与矿化速率方法研究论文。介绍了3种常用Po形态测定技术(连续分级法、酶水解法和核磁共振法)和近年来兴起的3种Po矿化速率测定技术(同位素稀释技术、连续观测-差减法和模型法)的基本原理,分析了几种技术适用范围、主要优缺点和互补性。尽管目前仍无针对土壤Po形态组成和矿化速率“最佳”测定方法,但是,研究人员可根据待测土壤理化性质和实验目的选择“合适”的测定技术。提出未来应在酶水解技术标准化、^(13)C和^(31)P核磁共振技术联用、发展包含植物因素Po矿化速率测定技术、联用形态和矿化速率测定技术等方面开展深入研究。
文摘【目的】通过大豆盆栽试验,研究了秸秆生物炭与磷肥添加对红壤团聚体稳定性、磷组分分布与植物磷吸收的影响。【方法】试验包括6个处理:P0(不施磷和生物炭)、P30(30 kg P hm^(−2),不施生物炭)、P90(90 kg P hm^(−2),不施生物炭)、BP0(不施磷,单施4%生物炭)、BP30(30 kg P hm^(−2),施4%生物炭)和BP90(90 kg P hm^(−2),施4%生物炭)。采用湿筛法分离得到粗大团聚体(>2 mm)、细大团聚体(0.25~2 mm)和微团聚体(<0.25 mm)并用连续浸提分级测定了不同团聚体中磷组分分布特征。【结果】①与P0和P30相比,BP0和BP30处理显著促进粗大团聚体形成与稳定,同时促进大豆生长与磷吸收,且BP30处理增幅最大。②与不施生物炭相比,不同磷水平下添加生物炭均显著降低粗大团聚体全磷、总有机磷、NH4F-Po和NaOH-I-Po含量,同时增加细大团聚体HCl-P_(i)和NaOH-II-P_(i)含量与微团聚体总无机磷、HCl-P_(i)和NaOH-II-P_(i)含量。③植株磷吸收与粗大团聚体总有机磷、NaOH-I-Po和NaOH-II-Po显著负相关,但与微团聚体和细大团聚体NH4Cl-P_(i)、HCl-P_(i)和NaOH-II-P_(i)显著正相关。【结论】生物炭与低量磷肥配施可有效改善红壤团聚体结构与稳定性,同时促进大团聚体有机磷的活化与微团聚体无机磷的固持,保障作物磷素供应。
基金Supported by the National Natural Science Foundation of China(11161049)
文摘In this paper we consider a discrete fractional boundary value problem(FBVP for short). We provide a delicate analysis for the property of Green’s function. Our analysis motivates the study of discrete fractional boundary value problems with fractional boundary conditions. As an application, we give conditions under which such problems admit at least one positive solution. Our results extend the results presented in [4].
基金financially supported by the National Key R&D Program of China (2017YFD0200200 and 2017YFD0200202)
文摘The concentration and components of manure phosphorus(P)are key factors determining potential P bioavailability and runoff.The distribution of P forms in swine,poultry and cattle manures collected from intensive and extensive production systems in several areas of China was investigated with sequential fractionation and a simplified two-step(NaHCO3-NaOH/EDTA)procedures.The mean total P concentration,determined by the sequential fractionation procedure of intensive swine,poultry and cattle manure,expressed as g·kg–1,was 14.9,13.4 and 5.8 g·kg–1,respectively,and 4.4 g·kg–1 in extensive cattle manure.In intensive swine,poultry and cattle manure about 73%,74%and 79%of total P,respectively,was bioavailable(i.e.,P extracted by H2O and NaHCO3)and 78%in extensive cattle manure.The results indicated the relative environmental risk,from high to low,of swine,poultry and cattle manure.There is considerable regional variation in animal manure P across China,which needs to be considered when developing manure management strategies.
文摘In this article, we discuss the existence and uniqueness of solutions for a coupled two-parameter system of sequential fractional integro-differential equations supplemented with nonlocal integro-multipoint boundary conditions. The standard tools of the fixed-point theory are employed to obtain the main results. We emphasize that our results are not only new in the given configuration, but also correspond to several new special cases for specific values of the parameters involved in the problem at hand.
