摘要:

Abstract.Simple equations are presented to predict the movement of a solute front in response to a given net cumulative flux of water. These equations do not require the assumption that the water content is at field capacity following water inflow, but may be simplified to that case. Equations are presented both for inert solutes and for anions and cations that react with soils through which they pass. The use of the equations is illustrated with simple hypothetical examples and, in one case, with field data.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1988.tb00746.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Simple predictions of deep drainage in the soil profile are often required for preliminary planning of land management where the cost of direct measurement is not warranted. Soil hydraulic conductivity and drainage of water below the root zone can be related to the salt content at the bottom of the root zone, assuming steady‐state balances of water and salt. A physically based empirical model uses readily measured soil properties to predict the quantity of drainage below the root zone under varying regimes of water management and shows a good relationship with ponded infiltration rat

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1988.tb00747.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The applicability of the ‘threshold concentration’ concept in formulating guidelines for irrigating with saline water was tested under field conditions on red‐brown earths from different field experiments in south eastern Australia. Infiltration of water in the field and the effect of rainfall impact were studied using ring infiltrometers and a rotating‐disc rainfall simulator.Three threshold concentration lines relating sodium adsorption ratio (SAR) and total cation concentration (TCC) in soil extracts were tested. These lines were based on laboratory tests of soil permeability, spontaneous dispersion and mechanical dispersion. They were found to predict the infiltration problems due to rainfall impact under three different surface soil conditions ‐ bare soil without cultivation, soil with no tillage and complete crop cover, and cultivated soils without any crop cover.Infiltration rates in continuous pasture plots were predicted by the threshold concentration line of spontaneous dispersion except in a high salt treated soil where reduced plant growth affected evapotranspiration and water intake during inf

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1988.tb00748.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The soil solution may contain both plant nutrients and toxic ions. The total salt concentration affects both osmotic pressure and plant water stress. This review describes the main methods of evaluating soil salinity. They are listed as extraction methods (saturation and other soil extracts, suction cups), displacement methods (pressure membrane, centrifugation) and electrical methods of total salinity measurement (salinity sensors, four‐electrode methods and time‐domain reflectometry). The methods are compared so that the reader may choose the one most suitable for his purpose, based on cost, on the inherent advantages or drawbacks of the methods themselves, on his need for single or repeated measurements and either estimates of total salinity or the concentration of selected i

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1988.tb00749.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Cracks in dry saline montmorillonitic clay allow the soil to wet rapidly when flooded with negligible redistribution of salts. Once closed the only effective pathways remaining for the movement of leaching water are old root channels and faunal burrows. However, their effectiveness in conducting water and for leaching is severely restricted because of the lack of horizontal connections between them. Restructuring of clay can introduce sufficient permeability to a depth of about 0.7 to 0.8 m to allow salt to be leached provided that the soil's initial moisture content is sufficiently large to prevent disintegration upon wetting (about 24%) and that the clay is not allowed to become unsaturated during the leaching.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1988.tb00750.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The leaching of salt from a restructured saline heavy montmorillonite clay soil was studied experimentally. Restructured clay was placed in a 25‐m long ± 0.75‐m deep polythene‐lined trench and leaching studied under flood irrigation. The hydraulic conductivity of the soil always exceeded 25 m d‐1during the experiment, and 85 % of the salt was leached within 16 days, most being leached in the first 8 days. The results indicate that restructuring clay could make the drainage of heavy clay soils economically

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1988.tb00751.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY