摘要:

SUMMARYA simple model to predict nitrate leaching developed by Burns (1974) was tested. The measured and calculated nitrate concentrations in 100 cm wet sandy soil profiles were compared: the results showed reasonably good agreement between the two values. Adjusting the initial conditions and reducing the segment size from 10 to 5 cm did not improve the accuracy of the prediction. Better agreement was, however, obtained when only the samples above the groundwater table were considered.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1984.tb00608.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYThe rate of hydrolysis of urea in soil over the wide range of concentrations, up to 10 moles N per dm3soil solution, found in fertilizer practice, was examined in Begbroke sandy loam adjusted to different pH values.On rewetting air‐dry soil, urease activity increased rapidly, reached a maximum within the first 24 h and then decreased slowly to level off after about 4 days. Pretreatment of the soil with urea or ammonium had no effect on the urease activity.Urease activity increased with substrate concentration, reached an optimum value and then decreased with rising urea concentration. The results could be explained by substrate inhibition at higher urea concentrations, and the data are well described by a modified Michaelis‐Menten equation involving three parameters,Vmax, KmandKiwhereKiis an inhibition constant.Kmdecreased linearily with rise in pH whereasKiincreased slightly between pH 4.9 and 7.0 and steeply between 7.0 and 8.4.Vmaxincreased with rise in pH, reached a maximum value at pH 6.0 and then declined at higher pHs.There was a further reaction, reaching a maximum rate at a urea concentration of about 0.2 molar N in the soil solution, that followed Michaelis‐Menten kinetics.Kmfor this high affinity reaction increased up to pH 7.2 and then decreased at higher pH values;Vmaxincreased up to pH 6.8 and then decreased. The contribution of the high affinity reaction was small except at low concentrations of

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1984.tb00609.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYA model for predicting the concentration profiles of urea, ammonium and soil pH in a soil column following diffusion from a surface application of urea is developed, using independently derived parameters, and tested experimentally.The following processes within the model were studied separately under the same conditions as those in the diffusion run. The rate of urea hydrolysis as a function of substrate concentration and pH in the soil solution, and the sorption of urea and ammonium by the soil from solution. A theory for the propagation of changes of pH in soils was applied to describe the diffusion of soil alkalinity arising from urea hydrolysis.These processes were linked by three diffusion equations—for urea, NH4and soil alkalinity, which were solved numerically using finite difference methods. There was good agreement between experimental and predicted concentrations of urea and NH4, and soil pH values at the two times teste

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1984.tb00610.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYCalcium nitrate fertilizer containing 92.3 atoms % excess nitrogen‐15 was applied on 5 May 1981 at a rate equivalent to 100 kg N ha−1to a clay soil in southern England cropped to winter wheat. Samples of the soil gases were collected frequently during the following 3 weeks. The soil oxygen concentration declined to 5% after 60 mm rain. A maximum of 1.5 ± 0.5 atom % N‐15 enrichment in labelled N2gas (29N2) was detected in the soil atmosphere on 28 May. Total denitrification losses, calculated from air‐filled pore space and rates of gas loss from the soil estimated using a Fick's law approximation, were 9.5 kg N ha−1with a daily rate of 0.30 ± 0.07 kg N ha−1. Estimated total losses were greater than 30 kg N ha−1, 93% in the form N2, but the estimation depends on several assumptions about the amount of double labelled gas (30N2), rates of gas dif

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1984.tb00611.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYThis series of papers examines some significant differences in the constitution of organic matter found amongst major soil groups and their genetic and morphological horizons, as determined by the dynamic pyrolysis‐mass spectrometry of whole soil samples. Multivariate methods of data analysis identify groups of co‐variant mass ions which successfully partition samples in terms of the above soil categories, and correlate with other major properties such as humification and hydromorphism.This first study covers the A horizons from a group of 22 Scottish soils chosen from the major temperate soil groups including brown forest soils, podzols, and noncalcareous, peaty and humic gleys (phaeozems, cambisols, podzols and gleysols). The principal components analysis of 52 mass ion intensities was found to partition the soils successfully in terms of two main factors which represented 62% of the total statistical variance.The first factor was found to correspond closely to the extent of hydromorphism, being high for highly gleyed A horizons, and depended chiefly on the presence of aromatic hydrocarbon ions. The second factor corresponded to the extent of mull humus formation, being high for brown forest soils (phaeozems, cambisols) and low for podzols, and depended chiefly on the abundance of polypeptide products relative to polysaccharide products. This second factor was evidently a more comprehensive expression of a humification factor found in previous studies.The relationships of these factors with C and N content and with base status properties were exami

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1984.tb00612.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYMagnetite grains in lateritic saprolite have alteredin situto porous hematite (martite) grains. Hematite occurs as relatively large (∼ 1 μm) platy crystals, triangular arrays of small (0.01–0.05 μm) lathlike crystals and very small (<100 Å) platy anhedral particles. Titanium increased in altered grains and may substitute for Fe3+in hematite. Mn, V, Cr and Zn remained approximately constant whereas the Ni content decreased. Halloysite crystallized from soil solution within pores resulting in a marked increase in the Si and Al contents of

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1984.tb00613.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYThe iron oxide mineralogy of 15 placic horizons from Germany, New Zealand, Belgium and U.K. was determined by differential X‐ray diffraction (DXRD). All samples examined contained ferrihydrite and goethite, lepidocrocite occurred in 10, and six contained non‐DCB‐reducible, lithogenic hematite. Ferrihydrite was most readily identified in ‘untreated minus oxalate‐treated’ DXRD patterns. Al‐substitution of goethites ranged from 4 to 13 mole %. Mean crystallite dimensions varied from 11 to 21 nm and from 6 to 21 nm for the goethite (110) and (111) lines respectively, from 7 to 51 nm for the lepidocrocite (020) line (lath thickness), and from 55 to 134 nm for the hematite (104) line. These values are typical for goethites from carbon‐rich environments with poor crystallization conditions, and for well crystalline lithogenic hematites. The DXRD method is ideally suited to the evaluation of the many selective dissolution techniques used in soil chemistry

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1984.tb00614.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYThe distribution of the total copper contents of 4179 samples from 946 Scottish soil profiles is reported and the relation of copper content to some other soil variables is examined.The frequency distribution of copper contents is found to be approximately lognormal. The derived mean for the full set of data is 10 mg/kg and the normal range 0.93–110 mg/kg.The copper contents of basic and intermediate igneous rocks exceed those of acidic rocks by a factor of about 5 and among sedimentary rocks copper contents are higher in argillaceous than in arenaceous types.The general trend is for copper to increase with increasing depth and ash content and to decrease with increasing sand content.On the basis of total copper content the risk of copper deficiency is assessed to be high in 26 soil associations in Scotland and moderate in a further 10. Naturally occurring copper toxicity is unlikely to be encountere

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1984.tb00615.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYSoil properties relating to the sediment volume of Ando soils varied depending on their physical state. The water content is a useful index property for the sediment volume of field‐moist soils. The sediment volume of air‐dried soils increased with decreasing clay content and with increasing organic carbon content. The water retention at 52% relative humidity was related to the sediment volume of soils subjected to a sonic wave treatment. An explanation of this behaviour is given in terms of the tendency of Ando soils to form water‐stable aggre

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1984.tb00616.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYThere is a correlation between variations in the clay mineral assemblages of the Crackington Formation (Upper Carboniferous) shales in parts of Devon, and the soil series mapped in the same areas. The differences in soil‐forming characteristics of the shales are not due to mineralogy alone, but to various states of diagenetic induration which they have achieved. Brown earths (Dunsford series) are formed on steeper slopes of more durable, illite‐chlorite dominated shales, whereas clayey soils (Tedburn and Halstow series) are typical of flatter, more poorly drained slopes of weaker illite and illite‐kaolinite clay mineral assemblages. This result adds the geological component to earlier views that the different soil series are simply a consequence of physiographic and hydrologic pos

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1984.tb00617.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY