摘要:

Abstract.Finely ground limestone waste from lead mining is discarded as useless but could be a valuable alternative to agricultural limestone. A glasshouse pot experiment established that it is an effective liming material. Two kinds were used: one from north Wales (HMT) represented metal‐rich waste produced by the older water‐gravity separation of ores; the other (NLB) was a modern flotation tailings. A commercial lime (CLS) was used for comparison. The materials were applied to an acid soil in quantities sufficient to raise the pH to 7 (single liming) and at much greater rates equivalent to annual limings for 369 years. All treatments were replicated five times and the soil/lime mixtures were analysed for EDTA‐extractable lead, zinc and cadmium. Radish was grown as the test plant and hypocotyl and leaf tissue were analysed for the same metals. The larger additions of HMT and NLB caused chlorosis and decreased yields. The cadmium and lead concentrations of leaves and hypocotyls suggested that the HMT material could be safely applied to soil annually for 79 years and NLB for 277 years. It is concluded that NLB can be used as agricultural lime

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00928.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Leaching of nitrate from a sandy loam cropped with spring barley, winter wheat and grass was compared in a 4‐year lysimeter study. Crops were grown continuously or in a sequence including sugarbeet. Lysimeters were unfertilized or supplied with equivalent amounts of inorganic nitrogen in calcium ammonium nitrate (CAN) or animal slurry according to recommended rates (1N) or 50% above recommended rates (1.5N).Compared with unfertilized crops, leaching of nitrate increased only slightly when 1N (CAN) was added. Successive annual additions of 1.5N (CAN) or 1N and 1.5N (animal slurry) caused the cumulative loss of nitrate to increase significantly. More nitrate was leached after application of slurry because organic nitrogen in the slurry‐was mineralized.With 1N (CAN) the leaching losses of nitrate were in the following order: continuous spring barley undersown with Italian ryegrass

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00929.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Rural agricultural areas in southern Ontario, Canada, with potential for aggregate extraction have become a focus of conflict over proposed land use change. Geophysical and soil physical field measurements were used to map soil variation for quantitative land evaluation at the farm level. Apparent electrical conductivity of terrain was shown to be strongly correlated with depth to the groundwater table on two separate test sites. A digital terrain model was used to create thematic maps of the predicted pre‐growing season soil water regime by contouring irregularly spaced electromagnetic survey and soil inspection points. Overlay analysis with a geographical information system (GIS) was used to produce an agricultural soil capability map for crop production. Adoption of a larger map scale provided significant refinement in detail over the published Canada Land Inventory soil capability ratings for agriculture, but both showed that Class 2 soils are dominant. The approach can improve the reproducibility of land capability assessment

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00930.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The effects of increasing periods of mechanical cultivation on soil properties under maize and cassava are compared with those under savanna in south‐western Nigeria. Bulk density is significantly greater under cultivation and total porosity, pH, organic matter and extractable nutrients are all significantly less than under savanna. However, the amounts of nitrate‐nitrogen and extractable nutrients do not show clear decreases with increasing mechanical cultivation. As the periods of mechanization increase, changes in most soil properties indicate increasing soil degradation. The implications of these results for agricultural policies in Nigeria arc discus

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00931.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The infiltration and runoff responses of degraded and non‐degraded semi‐arid land surfaces were investigated by rainfall simulation in the Lowveld of Swaziland. The hydrological response of the soil was controlled by changes in the properties of the soil surface, the nature of which was dependent upon rainfall intensity and antecedent moisture, as well as upon soil type and condition. Rather than there being one final steady‐state infiltration rate for a given soil type and condition (i.e. a constant of soil response), the final rates achieved were variable for each soil type and condition, and depended upon rainfall intensity and antecedent moisture. The implications of this for soil use and management in terms of infiltration measurement and runoff assessment are consi

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00932.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The contribution of agriculture to the nitrogen pollution of surface and ground waters of calcareous lake soils in the Kopais area (190 km2) of Greece was studied over three cropping seasons. Sample fields were chosen from seven representative soil units under different crop rotations. The distribution of mineral N (NO3‐N + NH4‐N) throughout the soil profile and the concentration of NO3‐N in the ground water and drainage water were measured and allocated to 6‐month winter or spring periods. For all fields N was leached to the deeper soil layers and to the saturated zones by both excess winter rainfall and spring irrigation of different crops The amount of nitrogen leached depended on the amount of nitrogen fertilizer applied; the depth of leaching varied with the physical properties of the soils. Losses in individual fields accounted for the equivalent of 17.6–80.8% of the nitrogen applied to maize and 70.5–94.1% of that applied to wheat. For the whole region estimated minimum N losses ranged from 175, 912 to 783, 564 kg for the 6‐month period. Nitrate concentrations in the ground and surface waters were often more than the EC target lev

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1993.tb00933.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY