摘要:

Abstract.Disjunctive kriging provides minimum variance estimates of properties from non‐linear combinations of spatially correlated sample data. In addition it can be used to estimate the conditional probability that some critical threshold is exceeded or that there is a deficit at unsampled points. The technique has been applied to estimate and map the salinity of the soil in the Bet Shean Valley of Israel from measurements of electrical conductivity. In November 1985 the estimated electrical conductivity of the soil exceeded 4 mS per centimetre throughout most of the region, and in only a small area was the probability of salinity less than 0.2. By March 1986 the electrical conductivity had declined everywhere to less than 4 mS per centimetre, and the conditional probability of exceeding this value nowhere exceeded 0.25. Despite the fluctuation in salinity farmers seem to have it under control. The results suggest that winter wheat is likely to germinate poorly in the saltier parts of the region and that lucerne (alfalfa,Medicago sativa)is unlikely to yield its maximum over most of it. Cotton, a summer crop sown in spring, should not suffe

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00817.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe co‐regionalization between relative elevation and zinc concentration was used to map zinc concentration in the soil of the Geul floodplain in the southern Netherlands by co‐kriging from 154 observations. Point co‐kriging and point kriging for estimating zinc content in the soil were compared in terms of kriging variances. Another 45 samples were used to compare the precision of the estimated values in terms of squared and absolute estimation errors. Point co‐kriging produced better estimates of zinc concentration than either simple point kriging or linear regression from the relative elevation data alone. Moreover, the estimation variances for co‐kriging are substantially smaller than those for kriging. The results suggest that knowledge of geomorphological processes can often improve the quality of interpolation maps of properties that are expensive t

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00818.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.Wet and droughty soils and those on steep slopes are now marginal for agriculture in Denmark. A nation‐wide map of these soil types has therefore been made to show their distributions. This was based on an existing soil database containing maps and analytical data. The paper describes the methods used to extract and display the dat

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00819.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.To allow land planners and managers to assess erosion under alternative management practices a model has been developed. It is based on the universal soil loss equation but uses subfactors for crop cover and management. Readily available agronomic data and field expert opinion were used in formulating the method. Locally‐derived data are used to validate the model which is then applied to agricultural systems in New South Wales, ranking the relative erosion hazard associated with crop and land management practice

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00820.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.The 296 soil associations of the National Soil Map of England and Wales are placed into five categories of erosion risk. These are based on land use, landform and soil properties and take into account the extent of erosion in the uplands, and its frequency, extent and rates in the lowlands. Erosion of arable land is by water or wind, but in the uplands frost action and disturbance by sheep are also important. A large proportion of arable England (36%) is at moderate to very high risk of erosion, including much of the better drained and more easily worked land, especially sandy soils. In the uplands thin soils or deep peats are most at risk. If land use changes, because of increasing intensification of agriculture or in response to climatic changes, many soil associations will become more at risk of erosion.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00821.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.Four lithological types of chalk are recognized. Normal white chalk has 34–50% porosity, nearly all of which holds water conventionally‘available’to plants. Hard chalk and grey chalk have less porosity and available water; chalk marl has very little available water. Significant capillary rise from below the root zone can be expected in normal white chalk only, and is not halted by fragmentation. Chalk has little N and usually little P. Only grey chalk and chalk marl have much ettractable K and Mg. These also slake, impeding roots. Thus, fertilized plants tolerant of high pH can grow well on normal white chalk debris, but on raw chalk marl, e.g. Channel Tunnel spoil, they need irrigation. Interesting plants volunteer on chalk debris, even on slaked chalk marl by th

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00822.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.The aluminium (Al), iron (Fe) and Dissolved Organic Carbon (DOC) contents of the soil solution were monitored in two upland grassland and afforested podzol soils in Mid‐Wales. Al organo‐metallic complexes predominated in the O horizon leachates of the grassland soil, whereas inorganic monomeric Al forms dominated in the lower mineral horizons. Dissolved organic matter determines the chemistry, solubility, and transport of Al and Fe in the O horizon, and these are under strong biological control. The distributions of organic‐Al, Fe and DOC within the soil profile were consistent with traditional podzolization theory. Observed increases in the molar ratios of Al:DOC in solution in the lower soil horizons may be responsible for the small solubility of Al organo‐metallic complexes in those horizons. Afforestation increased the concentrations of organic‐Al and Fe in the soil solution as compared with the concentrations observed for the grassland soil. Clearcutting further significantly mobilized Al and Fe from the upper soil horizon, primarily by increasing the DOC concentration in the s

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00823.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.A rotation trial of four years’ pasture followed by two years’ arable was used to study the effect of cropping on the morphological and hydraulic properties of soil. An adjacent paddock in grass for the past 35 years was included as a permanent pasture reference. Initial infiltration and field saturated hydraulic conductivity (Kfs) were least for cultivated soil and increased with increasing time under pasture. This could be explained by the contrasting porosities of resin‐impregnated blocks of undisturbed soil which had been infiltrated with methylene blue dye. SmallKfsvalues for cultivated soil resulted mainly from a thin surface crust, although pore discontinuity at the depth of the cultivation pan (130 mm) could also have contributed. GreaterKfsvalues under short‐term pasture resulted primarily from water flowing through biogenic pores connected to the surface. The greatestKfsvalues were in soil that had been under pasture for 35 years (P35). This was attributed to flow through biogenic pores and fissures associated with the strongly‐developed subangular blocky structure. The amount of water that infiltrated the two‐ and four‐year pasture soils (P2 and P4) under ponding was 2.5 and 5 times greater, respectively, than the soil that had been cultivated for two years (C2).As irrigation duration cannot be varied under the border‐dyking system used on the Canterbury Plains, the interval between irrigations must be varied if the same total amount of water is to be applied to each of these soils through the season. The interval should be less for the cultivated soil than for those under pasture, and should increase with increasing time under pasture (i.e

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00824.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.Tillage and mulching effects on the environment of the seed zone and on growth of cowpea(Vigna unguiculata)seedlings in the humid tropics were studied at Ibadan, southwestern Nigeria, in the 1987 and 1988 late cropping seasons. The split‐plot design experiment had conventional tillage (ploughing and harrowing), reduced tillage (ploughing only), zero tillage and grass mulch treatments. Conventional and reduced tillage practices decreased initial bulk density and increased seedling emergence, root growth, dry matter yield and overall seedling performance. Addition of mulch increased the soil moisture in the root zone and significantly decreased maximum soil temperatures and diurnal fluctuations in temperature. This provided a more stable environment for seedling establishment and growth than the unmulched soi

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00825.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00826.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY