摘要:

Abstract.In south‐east England, no relation between cereal yield and soil depth is shown by field estimates or harvesting microplots with depths to compact chalk of 23–121 cm. Differences in yield of ryegrass and wheat grown in cylinders containing artificial profiles with different thicknesses of topsoil, subsoil, chalk rubble and clean chalk from the Panholes series on Middle Chalk were attributed almost entirely to different amounts of nutrients. Chalk fragments supplied about 20% by weight of moisture to plants, and topsoil and subsoil about twice as much. Laboratory studies confirmed that fragments of Middle Chalk from near Wye (Kent, UK) hold about 20% water under tensions between 30 and 1500 kPa, but showed that topsoil and subsoil hold slightly less than this. The discrepancy in estimating water holding capacity arises because profiles over compact chalk drain only slowly from saturation. In this wet state they are very vulnerable to water erosion. It was also observed that ryegrass roots under water stress can penetrate well rammed chalk rubble, and that substantial amounts of water can rise 20 cm through solid chalk within a few days. It is concluded that soil losses resulting from erosion over normal porous chalks diminish cereal yields only slightly provided nutrient levels are maintai

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00919.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Changes in amounts of macro‐(N, P, K) and micro‐nutrients (Fe, Mn, Zn and Cu) were determined in two calcareous soils amended over an eight‐month period with pig slurry applications ranging from 0 to 500 m3/ha, and planted in containers with green pepper (Capsicum annuum). Total N and exchangeable K increased after slurry applications of 300 m3/ha or more, and available P increased after the smallest application rate (100m3/ha). Maximum crop nutrient uptakes of 41, 40 and 91% for N, P and K occurred with the smallest dose of slurry. Large losses of N, ranging from 27 to 74% (mean 55%) of N added to soil, occurred with all slurry treatments. From 41 to 71% (mean 55%) of the total P added in pig slurry was fixed in non‐assimilable forms. Most of the K from the pig slurry was available to the plants. Most of the micro‐nutrients (Fe, Mn, Zn and Cu) from the slurry were immobilized in the soil, probably because of the high pH and the small amounts of organic matter in both the slurries and soi

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00920.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Soil workability and trafficability are frequently estimated from meteorological data. This paper discusses the importance of soil workability for crop production, and reviews the limitations of various models, especially their applicability for predicting the effects of climate change. Some models calculate the number of spring or autumn work‐days by combining meteorological and soil‐related factors. Most of these determine, either empirically or deterministically, daily soil moisture budgets from which workability is inferred. A shortcoming of this approach is that it requires critical soil moisture contents or potentials. Also there are problems with the persistence of water in the profile and with the allocation of rainfall events to specific days. Determining work‐days over seasonal periods avoids these limitations, but this approach is unsuitable for short‐term planning purposes. The value of workability models is difficult to gauge as they often apply to specific soil and climatic conditions. This limitation will increase under a changing climate. For example, soil properties, previously considered as intrinsic, may alter in a manner that invalidates some models. More work on the soil processes controlling workability is needed, and on how these will be affected by a changing

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00921.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The effect of Agri‐SC’ soil conditioner on the erodibility of loamy sand soils has been investigated at the Hilton experimental site, Shropshire, since March 1988. Factors measured have included runoff and erosion, soil structure, crust strength, splash susceptibility, aggregate stability, soil micromorphological properties, response to compaction and penetrometer resistance.Treatment decreased runoff and erosion rates, bulk density, splash erosion, crust strength and penetrometer resistance, and increased pore space and aggregate stability. The effects on crust strength, aggregate stability and bulk density were statistically significant. The results suggest that applications of ‘Agri‐SC’ could have beneficial effects for soil con

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00922.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Pollution by inorganic and organic substances is increasingly disrupting the natural functions of soils. Some soils seem capable of receiving and holding chemical compounds, at the same time retaining their ecological flexibility, but others are readily damaged and should be regarded as vulnerable to particular pollution scenarios.At the request of the Chemical Time Bombs (CTB) Project, the International Soil Reference and Information Centre (ISRIC) organized an international workshop to assess the feasibility of increasing awareness of ‘soil vulnerability’ by a mapping exercise for Europe (SOVEUR), at a scale of 1:5 M, with reference to selected organic and inorganic contaminants. The workshop participants outlined procedures for a GIS‐based approach to determining areas where vulnerable soils occur, and formulated proposals for the implementation phase of the SOVEUR programme. Funding is now sought for continuation of the work outlined in this

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00923.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Oxidation rates of pyrite in colliery spoil were measured under both field and laboratory conditions. Meld oxidation rates varied through the year, depending primarily upon temperature. Rates of acid release of 7–15 μmoles H+/day were measured in field lysimeters in the period May to November. Little oxidation of the pyrite occurred between November and May; the rates in the summer months were approximately 5–10 times those during die winter. The rate of oxidation in the summer was limited by the solubility of amorphous iron oxides. Slow oxidation during the winter is probably related to the inactivity ofThiobacillus ferrooxidansat low temperatures. The rates of acid production in the laboratory in the temperature range 0–18°C were similar to those in the field. Materials inhibiting pyrite oxidation should be added when oxidation rates are slow, so that they are not overwhelmed by large amounts

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00924.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The land of the Nigerian Institute for Oil Palm Research (NIFOR) main station in southern Nigeria was evaluated for suitability for oil palm cultivation by the FAO system using data from 12 pedons representing four soil series. The results indicate that although the climatic factors are near optimum and more than half of the pedons were potentially moderately (S2) or highly (S1) suitable, the current suitability is marginal (S3). The major limitations were soil fertility (K mole fraction, CEC) and particle size. In this and similar environments good soil management is required before substantial improvements in oil palm production can be achieved.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00925.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.. A soil crust, produced by applying 44 mm of distilled water at an intensity of 290 mm/h using a rainfall simulator, was sufficiently rigid to significantly decrease emergence of barley from 76 to 40% and of oil seed rape from 82 to 61%. If the crust was kept wet by regular application of water as a fine mist, its strength was significantly decreased, but emergence remained poor because of prolonged soil wetness. After mist‐spraying the crusted surface just before emergence, per cent emergence was greater than uncrusted controls.Application to the soil of a static pressure after sowing but without crusting either had no effect or increased emergence, probably because of improved seed‐soil contact. However, crusting of the compacted soil decreased emergence severely. If the crust was allowed to dry it became very strong (>300 kPa). Mist‐spraying at the time of emergence only also improved seed emergence almost to that in the uncrusted controls. Repeated mist spraying after crusting decreased the strength of the crust, but the resulting waterlogging decreased emergence to less than half those of the controls and of the treatments sprayed just before emergence only. Compared with other management techniques available for amelioration of crusted seedbeds, carefully timed fine spray watering seems to offer the best opportunity for ensuring rapid seed emergence comparable to that in uncrusted

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00926.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Book Reviewed in this article:The Evaluation of Land Resources By D.A. Davidson.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00927.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY