摘要:

Abstract.Analyses of soil and hay samples collected from the Park Grass Experiment at Rothamsted during the last 137 years indicate slow but significant increases in KCl‐ and EDTA‐extractable aluminium in soil and a sudden and very large recent increase in the concentration of aluminium in the herbage. The latter is associated with a sudden increase in the rate of acidification of the soil over the last 10–15 years and the mobilization of aluminium as the soil enters the aluminium buffer range ‐a Chemical Time Bomb. Such severe acidification from atmospheric inputs on a well‐buffered soil illustrates how quickly an apparently stable situation can change as a result of acid deposition. It highlights the need to protect soils and plants from the effects of acidification by decreasing acid inputs or

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1994.tb00458.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.The aggregate stabilities of a soil restored after opencast mining and an undisturbed soil were measured over a complete cropping year from the time of ploughing a grass ley in autumn. This was to examine the effects of various post‐restoration cropping regimes on soil aggregate stability and soil porosity. A wet sieving technique and a mild dispersion method were used to determine indices of soil macro‐ and micro‐aggregate stability, respectively. Air filled porosity at field capacity and crumb porosity were also determined. Removal, storage and restoration decreased macro‐ and micro‐aggregate stability. After restoration, the different grass managements i.e. cutting for silage and grazing, had similar effects on soil aggregate stability and maintained greater aggregate stability than the arable regimes. The pattern of fluctuation in soil macro‐aggregate stability over the year was similar under all crops at both sites, but at the restored site there was a decline in stability, and differences in the air filled porosity at field capacity developed between cropping regimes. Micro‐aggregate stability was less at the restored than at the undisturbed site and showed no seasonal variation or difference between cropping regimes. However, a difference in crumb porosity between cropping regime

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1994.tb00459.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.The effect of organic matter content and other soil properties on soil erosion in the Rogate area, West Sussex, UK, was assessed using a rainfall simulator. Thirty soil samples (Podzols, Brown sands, Brown earths, Alluvial gley and Podzolized brown sands) collected from eroded and uneroded fields were exposed to 50 mm/h and 70 mm/h simulated rainfall. The results show that organic matter content influences soil erosion, through its effect on the stability of aggregates.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1994.tb00460.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Bulk and undisturbed block samples of soil were collected from beneath five cricket tables and outfields managed by a local authority and used by local league cricketers. Thin sections made from the undisturbed blocks revealed considerable differences in soil structure and composition between the cricket tables. Topdressings of varying textures have been added to all the tables over the years. Texturally‐layered profiles have built up beneath three of the tables because the topdressings have not been mixed. Horizontal organic mats often occur within and between the associated platy aggregates. Rooting is shallow under these tables, and the lower compacted layers often contain evidence for restricted drainage at certain times during the year. At one site, and to a lesser extent at another, greater mixing of the topdressings has been achieved by earthworms, but these seem to have been eradicated at the other sites. Although they create a better plant‐growing medium, the earthworms seem to have had a detrimental effect on the playing quality of the cricket ta

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1994.tb00461.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Soil hydraulic conductivities are frequently required for process‐based modelling of the soil water regime. Field‐saturated hydraulic conductivity was measured with the Guelph permeameter in 10 soil series with a range of structures and textures. The permeameter offers a range of options for calculating conductivities depending on soil conditions, particularly homogeneity of pore distribution within each horizon. However, even horizons described as massive or apedal were not sufficiently homogeneous to satisfy the boundary conditions entirely.Hydraulic conductivities were calculated by the one head, fixed α* procedure; α* is an index of capillarity. No direct correlations were found between hydraulic conductivity and land use. However, the average hydraulic conductivity of coarse textured topsoils which were mainly under arable agriculture was less than that of the finer textured topsoils largely under grassland. Even limited structural development increased the hydraulic conductivities of fine textured, compact subsurface horizons. It is important to match the adopted procedure to the soil conditions both during the determination of flow rates in the field and in the subsequent ana

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1994.tb00462.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Physical and chemical properties were compared during 1992 in adjacent bio‐dynamic and conventionally managed Haploxeralfs under improved, summer‐irrigated pastures in the Goulburn Valley of N.E. Victoria. Intensive dairy production has been practised on both the farms since the early 1950s, and aspects of the bio‐dynamic method have been practised on one farm for the past 18 years. Particle‐size analysis showed that the soil profiles of each field are derived from similar parent materials. The bio‐dynamic soil had greater macro‐porosity to a depth of at least 420 mm, lesser soil strength at 60, 120 and 200 mm, smaller dry bulk density values between 120 and 200 mm and larger organic matter content in the upper 50 mm. Volumetric soil water content measured along three transects to a depth of 1.4 m in the summer showed that the bio‐dynamic field was drier at depths greater than 200 mm. After heavy rains during the winter, the conventionally managed soil had an air‐filled porosity unfavourable for plant roots (2%) at 200 mm depth, whereas the bio‐dynamic soil was marginal for root growth (7%). The more favourable physical and chemical properties in the bio‐dynamic soil may be attributed to less grazing pressure, longer intervals between irrigations, use of the bio‐dynamic horn‐manure preparation, intermittent compost applications, less tractor traffic and the encouragement o

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1994.tb00463.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Leaching losses of solutes can be calculated if two variables, the amount of water passing through the soil and the concentration of solute in that water (a flux concentration), are known. Two simple approaches, soil extraction and suction cup sampling, were used to estimate the concentration of solutes in the water moving through a silt loam soil. The results were compared with actual concentrations measured in the drainage water from a sub‐surface (mole‐pipe) drained soil.Seasonal leaching losses were calculated as the sum of the products of estimated monthly drainage and the estimated average monthly solute concentration in the soil solution. These results were compared with the leaching losses measured in drainage water from the mole‐pipe system. For non‐reactive solutes such as bromide (an applied solute) and chloride (a resident solute), the suction cup data provided better estimates of the leaching losses than did the soil extraction data. The leaching losses calculated using volume‐averaged soil solution concentrations (obtained by soil extraction) overestimated the loss for the resident solute, but under‐estimated the loss for the surface‐applied solute. On the other hand, the data for non‐reactive solutes suggest that measurements on suction cup samples may be representative of the flux concentration of a solute during leaching. For nitrate, a biologically reactive solute, there was no clear pattern in the differences between the estimated and measured leaching losses. The flux‐averaged concentration in the drainage water was about midway between those measured in the suction cup samples and in

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1994.tb00464.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Book reviews in this article:Soil organic matter dynamics and sustainability of tropical agriculture. Edited by K. Mulongoy&R. Merckx.World soil erosion and conservationEdited by D. Pimental.Fundamentals of soil behaviour (2nd edition)By James K. Mitchell.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1994.tb00465.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY