摘要:

SummaryA technique is discussed whereby the level of mineral nitrogen present in the soil after incubation has been used to estimate differences in the nitrogen status of an arable soil after leys. There was an appreciable increase in the mineralization of nitrogen in arable soil after 3 years under ley, despite any immobilization which may have resulted from the decomposition of grass roots. The uptake of nitrogen by the winter wheat which followed the leys was closely related to the nitrogen status of soil so determined.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1962.tb00684.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SummaryHydromorphic humus podzols can develop under submerged conditions as a result of internal water movement, and their development is by no means dependent on the occurrence of a water table which descends, periodically, below the B horizon. The basic difference between podzolization under anaerobic and aerobic conditions is stressed, and it is suggested that classification of the podzols be based in the first place on these two processes, using the humus content of the B horizon for a further subdivision. It is pointed out that the humus content of the B horizon is unsuitable for the primary subdivision since it is governed by a number of independent factors.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1962.tb00685.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SummaryPressures exerted against a confining restraint by Na‐montmorillonite in equilibrium with NaCl solutions were measured. The swelling pressures decreased with increasing NaCl concentration as predicted theoretically, but the rate of decrease was lower than calculated so that the ratio of observed to calculated pressure increased with increasing salt concentration.These larger swelling pressures could result from a higher activity of the ions between interacting clay particles compared with the ions in the neutral salt of the dialysis solution. It is then not necessary to postulate a non‐osmotic force of repuls

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1962.tb00686.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SummaryRecent reconnaissance soil surveys of proposed irrigation projects have revealed a belt of shallow soils overlying gypsum beds in the drier steppe zone of Northern Iraq.The soil profile consists of two sharply contrasting layers—upper layer of Mesopotamian Alluvium and a lower layer of highly gypseous material. The Mesopotamian Alluvium is a brown fine‐textured material, highly calcareous but very low in soluble salts, exchangeable sodium, and gypsum. The gypseous beds underlying this shallow soil mantle are relatively soft tertiary sediments (Fars beds) or their erosion products.Despite abundant evidence of the non‐toxicity of gypsum even in saturated solutions, observations on naturally occurring gypseous soil in steppe areas of Iraq and the U.S.S.R. show that root growth is inhibited where the gypsum content is 10 to 25 per cent, or higher, apparently because of poor transmission of air and water associated with bad structure.Agronomic and engineering problems were considered, together with U.S. data on rooting systems of climatically adapted irrigated crops, in arriving at a classific

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1962.tb00687.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SummaryMedian values for pH, conductivity, organic and inorganic carbon, exchangeable cations, and mechanical analyses are given for seven solod profiles and eight solodic profiles. They show the A and A‐B horizons of the solod to be moderately acid, the B1horizon to be very slightly acid to neutral, and the lower B and C horizons to be alkaline in reaction. Exchangeable Ca to Mg ratios vary from relatively high in the A to very low in the A‐B and B horizons. Exchangeable Na varies from low in the upper horizons to high in the lower. Mechanical analysis data show clay accumulation in the lower B horizons.The data for the solodic profiles are similar to the above as to pH, but the corresponding horizons are less acid. Exchangeable Ca to Mg ratios are very high throughout the profile, ranging from just over 4 in the upper A to less than 2 in the lower B. Exchangeable Na is very low throughout. Mechanical analysis data are similar to those for the solod profi

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1962.tb00688.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SummaryThree soil properties are proposed as criteria for distinguishing tropical and equatorial soils according to the age of their parent materials. The criteria are structure, silt‐clay ratios, and percentage of weatherable minerals. Assessments thus made agree well and conform closely to assessments based on geomorphology in Central Afric

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1962.tb00689.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

SummaryEvidence is presented to show that an upward movement of nitrate takes place in the Kikuyu red loam coffee topsoil during the hot, dry season following the main rain periods. This upward movement contributes towards the build‐up of nitrate which is observed to take place in the topsoil as it dries ou

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1962.tb00690.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY