沸腾时间对土壤缓效钾测定结果的影响

初步探讨了消煮时间、沸腾时间对土壤缓效钾测定结果的影响程度及其规律，确定了最佳沸腾时间为３．５～４．５分钟，同时掌握了相同条件下，消煮５分钟与１０分钟土壤缓效钾测值间的相互关系。     

石灰性土壤缓效钾含量检测浸提方法的改进

用硝酸提取方法测定石灰性土壤缓效钾含量过程中,在浸提溶液中加入一滴植物油作为消泡剂,可防止浸提液沸腾时溢出管口;用硬质大试管取代三角瓶,并用油浴取代电热板,每次浸提样品数量增加到60个左右,工作效率提高3～4倍.结果表明,浸提方法改进后,同一批样品浸提液开始沸腾时间前后相差5 s左右,浸提液温度基本稳定在103.8℃,平行样检测结果的变异系数在1.2%～2.4%之间,重复样检测结果的变异系数在1.2%～3.3%之间.用改进方法测定不同含量的石灰性土壤缓效钾时,与常规方法有85%的符合率.改进方法测定值与参比土样定值平均值的相对误差在0.4%～3.8%之间.     

辽宁省稻田土壤供钾状况研究

据测定,辽宁省水稻土速效钾、缓效钾的平均含量均以盘锦、营口地区的盐渍型水稻土为最高,其次是东港地区盐渍型、淹育型和潜育型水稻土以及铁岭地区淹育型水稻土,最低的是沈阳地区淹育型水稻土。各地区水稻土的供钾强度(Ⅰ)、供钾容量(Q)以及供钾缓冲力(Q/I),均按上述地区顺序依次递减。出现这些差异,是由于土壤成土母质、粘土矿物类型、钾肥用量、灌溉水水质以及土壤基本性质,诸如粘粒含量、阳离子交换量、pH值等因素不同而造成的。盘锦、营口稻区水稻土在这几方面都占优势。     

施钾对茶园土壤钾素及平衡的影响

盆栽选取四川、重庆典型的砂岩黄壤、灰岩黄壤、酸性紫色土为供试土壤,田间选取在砂岩黄壤上生长了25年的茶园,连续5年研究了施用钾肥(硫酸钾)对茶园土壤钾库及钾素平衡的影响。结果表明:施用钾肥能显著提高土壤钾库的各类钾素,但其绝对含量都呈逐年下降的趋势。土壤中各类钾素的变化因土壤类型而异,土壤各类钾素的增量均为灰岩黄壤砂岩黄壤酸性紫色土。不施钾肥(CK)的盆栽茶树、田间茶树分别每年从土壤取走钾素0.10.g/kg。盆栽三种土壤的钾素年平均流失量分则别为0.18.g/kg(灰岩黄壤)、0.09.g/kg(砂岩黄壤)、0.07g/kg(酸性紫色土),可见种植茶树施用K肥很有必要。     

定位连施土粪对土壤钾的影响

连续4年定位连施土粪表明，一年一作春小麦条件下，年施入土粪150000-225000kg/hm^2，能显著提高土壤供K量；年连施225000kg/hm^2土粪才能使土壤K素收支趋于平衡状态，低于此用量则是亏缺状态，按照目前生产上的正常用量75000kg/hm^2连施，土壤速效K减少17.5%，若土粪用量增至2-3倍可使土壤速效K含量提高47.8%-107.5%，但不能保持土壤缓效K含量。     

外源钾对三种不同土壤钾转化影响的研究

采用盆栽试验,在黄棕壤,砖红壤,黑土三种土壤上种植烟草,研究了外源钾对土壤中钾转化的影响,结果表明:在黄棕壤,黑土上,0.0-0.8 g kg-1施肥范围内,随着施钾量的增加,土壤中速效钾和缓效钾的总增量、作物的含钾量均在增加,尤其是在0.8 g kg-1施肥水平时,二者超出了施肥的增加量,说明施钾促进了其它钾的释放;三种土壤中粘土矿物含量为:黑土>黄棕壤>砖红壤。     

土壤不同形态钾含量与土壤颗粒的关系

土壤含K矿物同其他矿物颗粒一起均分布在不同粒级的土粒中,这些土粒在不同的土壤中构成了不同的配合比例,形成不同的土壤质地的属性。统计表明,<0.05mm与<0.01mm粒级间呈极显著线性相关(r=0.896**,n=92),相关分析表明,不同粒级的土粒与不同形态K间呈显著线性或曲线显著相关,而全K只与<0.05mm粒径的土粒呈极显著相关(r=0.234**,n=73),全K与速效K的数量关系通过全K、<0.05mm、<0.01mm粒级与速效K系统相关组合的算式以数学的方法计算速效K含量。     

An improved method for determination of adenosine triphosphate (ATP) in soil

Different methods for extraction of ATP from soil were examined. The methods were compared with respect to the efficiency of extraction of ATP from soil, and the content of ATP in the extracts was measured by the luciferin-luciferase system. The following extraction procedure was found to be the most efficient:Shaking of the soil with sulphuric acid, followed by filtration, cation exchange of the extract on Na⁺ resin, and adjustment to pH 9.8 with ethanolamine.The method is simpler, faster and more convenient for processing large numbers of samples, than the earlier-described acid extraction methods. Furthermore, ATP levels of 5ngATPg^?1 dry wt soil can be measured and results can be reproduced within ± 5%.The respiration rates of the soils were also measured, and a high degree of correlation was found between carbon dioxide production and ATP levels determined by extraction with sulphuric acid or dimethylsulfoxid.     

Simplification of the standard method for determination of non-exchangeable NH4−N in soil

The widely-used Silva-Bremner method for determining non- exchangeable NH₄?N in the soil was modified so as to reduce reagent requirement and the time taken to carry out the analyses. In the modification, boiling the mixture of soil and KOBr on a hot plate was replaced with heating the soil/KOBr mixture, directly placed in centrifuge tubes, in a boiling water bath or a microwave oven. The best procedure is to keep the soil/KOBr mixture for 10 minutes in the water bath or for 10 minutes at 50% of full power in a microwave oven. The modified method gave similar values to the standard method on 4 quite different soils and also slightly increased reproducibility.     

A simple turbidimetric method for determination of exchangeable soil potassium

Abstract

It was found that sodium tetraphenylboron, NaB(C₆H₅)₄, can be used as a reagent for determination of K in acid sodium acetate extracts of soils. After extraction and filtration, sodium hydroxide and formaldehyde are added prior to the reagent to avoid interference of ammonium. At low concentrations of K in the extracts (<30 mg K/1) the white precipitate of potassium tetraphenylboron, KB(C₆H₅)₄, is colloidal and the concentration of K can be determined turbidimetrically with a simple instrument in the field or on the farm.     

基于改进CNN的猕猴桃根区土壤含水率反演方法

为解决无人机遥感领域根据冠层光谱信息对猕猴桃果树根系土壤含水率（root soil water content, RSWC）进行反演时,现有算法对冠层图像信息分析不足的问题,该研究对传统卷积神经网络模型进行改进,提出一种复合视觉卷积回归神经网络（compound visual convolutional regression network, CVCRNet）,该网络复合两种不同尺寸卷积层对图像数据进行卷积特征提取,并使用全连接层对卷积特征值进行降维,从而直接以多光谱图像为分析对象对RSWC进行反演,充分利用多光谱图像内所有数据,提升反演精度。研究采集徐香猕猴桃果树果实膨大期（5—9月）冠层多光谱信息和深度40 cm处的RSWC,把基于图像的CVCRNet网络反演方法与基于植被指数的传统反演方法进行对比,CVCRNet训练结果在验证集R²为0.827,RMSE为0.787%,相较于传统方法在验证集R²为0.759,RMSE为0.983%,反演结果相关性有了明显提升,准确率也有得到一定提高。结果表明,改进后的CNN网络能够作为冠层信息反演的重要工具,在冠层复杂的场景下达成良好的土壤数据反演效果。     

测量土壤含水率的频域方法改进

For many years a soil water content sensor with low cost, reliability and sufficient accuracy has been desirable. Thus, an improved measurement method based on the frequency domain （FD） principle for determining soil water content was considered. Unlike other measurement principles, a new measurable index, η, which was independent of the output impedance and the amplitude of the oscillator while relying on the electrical impedance of a multi-pin probe, was proposed. Moreover, a model for processing the impedance of the multi-pin soil probe was developed, and several important electrical parameters for establishing their operating ranges applicable to this probe were evaluated. In order to confirm the theoretical analysis, an experiment was conducted with a 4-pin probe. Using the developed model, the relationship between the proposed index η and soil volumetric water content was shown to be linear （R^2 = 0.9921）. Thus, as the measurable index, η seemed satisfactory.     

四苯硼钠溶液中含钾矿物非交换态钾的释放特性研究

含钾矿物的全钾含量、非交换态钾总量以及非交换态钾的释放速率因矿物种类而异,且3种参数之间没有必然的相关性。供试5种含钾矿物非交换态钾总量由高到低的顺序是:金云母 5.19% 黑云母3.08% 蛭石2.01% 白云母1.18% 钾长石0.24%,占各矿物全钾的比例分别为:58.4% 、99.7% 、62.5% 、14.2% 和4.98% ,平均达48%。选择较弱提取力的四苯硼钠溶液进行非交换态钾的释放特性研究,5种矿物非交换态钾3d释放累积量顺序为:黑云母 蛭石 金云母 白云母 钾长石;非交换态钾平均释放速率也表现为同样的顺序。上述5种矿物在弱提取力的四苯硼钠溶液中释放3 d,非交换态钾的平均释放速率分别为5.99、2.34、0.52、0.22和0.17 mg/(kgmin),差异明显。如何根据非交换态钾的释放量和释放速率来综合评价矿物钾的生物有效性是未来研究中需要明确的问题。     

An improved method for tracing soil erosion using rare earth elements

Purpose

The use of rare earth elements (REEs) as tracers provides a high-precision method for quantitative determinations of soil particle movement in soil erosion studies. In this study, a new calculation method was developed and tested to improve the precision of the REE tracing method and to expand the application of this method to areas with coarse-textured soils.

Materials and methods

This study used purple soil to simulate a catchment with data based on a field survey of a small catchment located in the Three Gorges Area in China. Eight different powdered rare earth oxides, which included La₂O₃, CeO₂, Nd₂O₃, Sm₂O₃, Eu₂O₃, Tb₄O₇, Ho₂O₃ and Yb₂O₃, were applied as tracers to describe soil movement in this scaled catchment during three simulated rainfall events of 1.0, 1.5 and 2.0 mm min^?1 rainfall intensity. Leaching experiments were conducted to investigate the vertical migration of REEs in soil layers. Particle size distributions (PSDs) and REE concentrations for each soil particle size class (1–2, 0.5–1, 0.25–0.5, 0.1–0.25, 0.075–0.1, 0.05–0.075, 0.02–0.05, 0.005–0.02 and <0.005 mm) were analysed to evaluate the precision of the proposed calculation method.

Results and discussion

Most REEs remained in the first layer during leaching. The scanning electron microscopy-energy dispersive X-ray (SEM-EDX) mapping images showed that more REEs were adsorbed by small particles (≤0.1 mm), with large specific surface areas, than by large particles (>0.1 mm). During the three rainfall events, the coarsest size classes (1–2 and 0.5–1 mm) of the sediment samples were less than that of the soil. In contrast, the other classes, including <0.075 mm, showed the strongest adsorption for REEs, and the weight percentage of grains in eroded sediment was more than that in the source soil. The accuracy of the new proposed calculation method increased by 24.37, 20.25 and 3.84 % for the first, second and third storm, respectively, compared with the uncorrected mass of soil loss from the scaled catchment.

Conclusions

The REEs bonded well with purple soil particles and the leaching of REEs from the tagged layer to the lower layers was minimal. The <0.075-mm particle size class had the strongest adsorption capacity for REEs. The soil loss estimates were improved with the new calculation method.

     

An improved force‐restore method for soil temperature prediction

The force‐restore method originally developed to enable soil temperature predictions assumes that soil is uniform with depth (i.e. the vertical gradient of thermal diffusivity is zero in soil) and that thermal conduction is the only heat transfer mechanism necessary for prediction of soil temperature. These assumptions hamper the applicability of the force‐restore method to many natural soil conditions. The main objective of this study is to revise the force‐restore method by extending it to include the possibility of soil heterogeneity with depth (i.e. non‐zero vertical gradient of thermal diffusivity in soil) and to include the possible occurrence of convective heat transfer as well as conductive heat transfer in soil. Soil temperatures calculated by the current and the revised force‐restore methods for a shallow soil layer were compared with measured soil temperatures at a bare soil site in the China Loess Plateau from 22 to 26 July 2005. Results showed that the revised method improved on the current force‐restore method, which overestimated either the diurnal amplitude or the phase shift for the shallow soil layer. These results indicate that the revised force‐restore method is more applicable than the current force‐restore method for predicting soil temperatures in naturally occurring non‐uniform soil. The revised force‐restore method has potential application within many land‐atmosphere numerical models.