摘要:

SummaryThe iodine content in successive 10 cm horizons of eighteen soil profiles from England and Wales was determined and correlated with contents of‘free’ aluminium and iron oxides (oxalate‐soluble) and organic matter.The pattern of change in iodine content with depth varied considerably with soil type. In the rendzina soils, the content was relatively high in the surface 10 cm but declined markedly with depth. In the podsols, iodine was low at the surface but increased in the B horizon: in one of these soils an iron pan of about 1 cm thickness had an iodine content as high as 37.6 mg/kg. In two soils derived from Ordovician, and one from igneous, rock material, the iodine content was relatively high (up to 25 mg/kg) with maximum values at intermediate depths. In contrast, soils derived from river alluvium and from lowland clays generally had low iodine contents (<6 mg/kg) which showed little variation with depth in the profile. In a peat soil the iodine content was relatively high in the horizons above 60 cm but was low (1. 3 mg/kg) in the underlying clay.In all 154 samples from the eighteen sites, iodine content was closely correlated with oxalate‐soluble aluminium (r= 0.834***) but not with oxalate‐soluble iron (r= 0. 35) or organic matter (r= 0.37). However, in the five most acidic soils, with pH below 4. 8, the iodine content was more closely correlated with iron than with

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02035.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummaryTypical rates of soil survey (area, length of boundary and number of observations per day or hour) are presented for routine surveys on 1:25,000 and 1:10,560 base maps by the Soil Surveys of Scotland, and of England and Wales, in five areas.The distance a soil surveyor walks between observations sites each day is highly correlated with (Area surveyed x No. of observation sites).

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02036.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummaryA method of defining soil macrostructure, based on observations of the distribution of aggregates and voids along horizontal transects, is combined with a model for the probability of a root either penetrating, or being deflected by an aggregate, after passing through a void. The latter is based on the strength of the aggregate, the angle of incidence, the length of the preceding void, and root properties. Effects of soil macro‐structure, aggregate strength and plant species are discussed.A good correlation was obtained between the predicted nutrient uptake per unit length of root and the measured uptake per plant from beds of different‐sized aggregates.The inclusion of the effect of aggregate strength on root elongation rate removed all effects of aggregate size on the rate of uptake of non‐mobile nutrients. In order to reconcile this result with the correlation mentioned above, it is hypothesized that greater root branching occurs in beds of smaller aggregates so that the nutrient uptake remains the same as it would have been in the absence of rate effects.It is shown that an optimum' soil macro‐structure exists for the maximum growth of roots of a given plant species. This optimum structure depends on the strength of the soil agg

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02037.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02038.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02039.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02040.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02041.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02042.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY