摘要:

SummaryThe mucilaginous material, which forms a layer several microns thick around plant roots, contains a glucan, a polyuronide, and heterogeneous polysaccharides. An assessment is given of the effects of the mucilage on ion and water uptake by plants, on soil chemical and physical properties including aggregation, and as an energy source for microorganisms. It is concluded that these effects are important but that more chemical and physical studies of plant mucilage are required.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02025.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummaryBecause of their organic matter content, the surface tension of water of soils is about 8 to 9 erg cm‐2(8 to 9 × 10‐7J cm‐2) less than that of pure water. It is estimated that the surface tension of soil solution is 63–64 erg cm‐2in the surface soi

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02026.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummaryThe water flow equation for two‐dimensional, unsteady infiltration from semicircular furrows in unsaturated soil is solved numerically with the aid of the alternating‐direction implicit (ADI) difference method. Laboratory experiments were conducted on infiltration from semi‐circular furrows into sandy clay loam sott contained in a model tank. Water contents measured at different locations for different times were in close agreement with the predicted moisture profiles and the locations of the wetting f

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02027.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummarySimple chromatographic equations were adapted to describe frontal water displacement by tracer‐containing water in soils where only partial displacement occurs. The equations were shown to give excellent agreement with experimental data in five field experiments where tracer was added in artificial rainfall. The consequences of partial displacement for soil water replenishment in the root zone, salt leaching and ground water recharge are discusse

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02028.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummaryA classification of structural condition in surface soils is proposed, based on the volumes of two categories of pore size, termed air capacity (pores greater than 60 μm diameter) and available water (pores of 60 to 0.2 μm diameter.Relationships of pore volumes to particle size class, organic carbon content and soil water regime are examined. Soil structural conditions are mainly affected by water regime and organic carbon and, apart from the extremes of sandy or clayey textures, less influenced by particle size distributio

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02029.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummaryThe pH0and ZPC of two Hydiandepts were determined by potentiomettic titiation in NaCl and by ion adsorption measurements from NH4NO3, respectively. The decrease of pH, pH0, and ZPC due to drying was explained by the hydrolysis reaction. Partial drying, high organic matter content, and low Al2O3concentration in the surface soil were responsible for its low pH, pH0and ZPC. The high pH0of subsoils was attributed to the presence of amorphous aluminosilicates and mixed polymeric gels of Fe(III) and A1 with high water content. The significant decrease of nitrate adsorption due to dehydration is discussed in relation to the change in pH, pH0, ZPC, and surface area on drying.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02030.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummaryIn 24 soils the CEC of untreated samples, of samples treated with hydrogen peroxide, and of samples treated with dimethyl sulphate, was determined at pH 3, S and 8. The CEC of clay and organic matter was calculated from multiple regression equations and compared with values after treatment with peroxide and after methylation. At pH 3 and pH 5 the CECs of clay by the three methods were similar, whereas at pH 8 they were significantly lower on untreated samples.The results are interpreted in relation to the formation of organo‐mineral complexes and to the interaction of the acid functions of the clay and organic matte

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02031.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummaryTheoretical relationships between pH, CO2partial pressure and alkalinity (bicarbonate + carbonate concentrations) have been shown to apply to solutions and calcite and soil suspensions.The exchange of Na onto three Ca clays shows that Ca is preferred but with negative free energies of exchange. With decreasing total electrolyte concentration, the preference for Ca increases, so that only when the concentration is above 10‐3M will significant amounts of exchangeable Na be found in soils. The preference for Ca is illite>montmorillonite>vermiculite.Dilution of the mixed Na‐Ca clay suspensions causes exchange, desorption of Na and. in some cases Ca. This desorbed or ‘alkaline’ Na (and Ca) is replaced by H some of which attacks the clays. The apparent hydrolysis coefficient, KG = H adsorbed (Na)/Na adsorbed (H), varies between 5 and 9 × 105, increases with increase in electrolyte concentration and varies in the order vermiculite>illite>montmorillonite. The concentration of alkaline Na + Ca increases with increasing ESP, and with clay type in the same order as the KG values. The pH calculated from the alkaline Na + Ca, assumed equal to the alkalinity was equal to measured values except for montmorillonite where the calculated values were low. Magnesium release by acid attack of the montmorillonite may explain the differences.Vermiculite rich soils will be most likely to accept exchangeable Na and to hydrolyse and develop al

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02032.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummaryHumic acids extracted from the Bh horizon of a kauri (Agathis australis) podzol and the A horizon of a yellow‐brown earth under hard beech (Nothofagus truncata), both New Zealand soils, were fractionated by a ‘salt boundary’ technique using a dextran gel, and the fractions hydrolysed with 6 M hydrochloric acid. Lignin‐derived phenolic acids were analysed by gas chromatography of the ether‐soluble hydrolysis products of the humic acids.The lignin derivatives from the kauri podzol humic acid are probably modern products derived from the present‐day scrub vegetation, whereas those from the yellow‐brown earth humic acid are derived from the deciduo

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02033.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SummaryThe major ether‐soluble products from the hydrolysis of humic and fulvic acids include levulinic, succinic and fumaric acids, accompanied by more variable amounts of 4‐hydroxy‐, 3‐methoxy‐4‐hydroxy‐, and 3,4‐dihydroxybenzoic acid. 3,5‐Dihydroxy‐benzoic acid was not detected in the hy

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1978.tb02034.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY