ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00787.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.tb00789.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.ALES, the Automated Land Evaluation System, is a microcomputer program that allows land evaluators to build their own knowledge‐based systems with which they can compute the physical and economic suitability of land map units, in accordance with the FAO's Framework for Land Evaluation. The economic suitability of a land mapping unit for a land utilization type is determined from the predicted annual gross margin per unit area. Increasing limitations result in increased costs of production, decreased yields, or both. Evaluators build decision trees to express inferences from land characteristics to land qualities, from land qualities to predicted yields, and from land qualities to overall physical suitability. A representative model is describe

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00790.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.Machinery was designed specifically for relay‐cropping on permanent raised beds (150 mm high and 1.5 m wide) in northern Victoria. This machinery enabled maize (Zea mays) to be successfully sown at 2, 4 and 5 weeks before harvest, and 1 day after harvest (Control), of wheat (Triticum aestivum). The sowing equipment consisted of a four‐row cultivator, behind which were four precision seeders. The wheels (250 mm in diameter) were spaced at 1.5 m to track along the base of the furrows. In one pass on each bed, the sowing equipment tilled two strips (each 50 mm wide, 30 mm deep and 50 mm from the outer row of wheat) and sowed maize, with little damage to the wheat crop. We extended the axle of the trailed harvester so that the wheels (250 mm in diameter) were 3 m apart, and moved the drawbar 300 mm to one side so that all wheels ran along the base of the furrows. There were no significant differences between treatments in yield (mean 2.9 t ha‐1) of dryland wheat, in final emergence percentage (mean 89%) or in early growth of irrigated maize. The maize yielded significantly less grain in the treatment sown at 5 weeks (9.6 t ha‐1), but not 2 or 4 weeks (mean 10.6 t ha‐1) before the wheat was harvested, than in the Control (10.8 t ha‐1). The wheat and maize yielded more grain than those grown traditionally as sole crops in northe

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00791.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.Four bullock‐drawn tillage implements (mouldboard plough, chisel plough, sweeps, and shovels) were evaluated on a hard‐setting Alfisol. Measurements included draft requirement, bulk density, cone index, soil crust strength, water content of the plough‐layer and crop yield. Changes in bulk density and cone index due to tillage decreased with time and were negligible by the end of the growing season. After tillage with a mouldboard plough the crust was stronger than after tillage with other implements. The shovel cultivator enabled the soil to store more water, and required least draft per unit effective area o

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00792.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.During 1986 erosion on soil mulched with 6 t ha‐1of straw was compared with that on soil maintained bare by herbicides in a mature apple orchard. The orchard was on well‐drained soil with a sandy loam top on a slope of 2°. Erosion was greatest in the alleys between the trees, where traffic had compacted and smoothed the soil. The mean annual soil loss on bare ground in the alleys was 0.45 t ha‐1; straw mulch reduced this by 85%. Erosion was worst between July and October, when rainfall>10 mm h‐1was most frequent. However, differences in soil moisture and resistance to infiltration may have also contributed to differences in erosion throughout

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00793.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.After restructuring of a heavy saline gypsum containing clay soil by intensive subsoiling to 0.7 m depth, it was possible to leach 60% of the leachable salts from the restructured soil in 28 days by inducing a lateral flow of leaching water through the soil profile.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00794.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.This paper describes experiments on the inhibitory effects of hydroquinone (HQ), phenylphos‐phorodiamidate (PPDA) and N‐butyl phosphorothioic triamide (NBPT) on the nitrification in soil. Incubations were carried out at 2/3 field capacity at 25°C of soil samples to which either ammonium or nitrite was added together with inhibitors. Addition of PPDA or NBPT did not influence the oxidation of ammonium. HQ. however, retarded the process significantly, and also the accumulation of nitrite. This was confirmed in experiments whereby added nitrite was followed. Some of the differences could be explained by changes in the soil pH. During incubation the evolution of the total mineral nitrogen was not importantly altered by addition of the inhibi

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00795.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.The properties of soil under 15‐year‐old plantations of gmelina (Gmelina arborea) and teak (Tectona grandis) were compared with logged forest soil in south‐western Nigeria. The soil was significantly denser in the 0–10 cm layer of plantation soil and total porosity less than that of forest soil. Organic carbon was significantly greater in the 0–10 cm layer of forest soil. Similarly, the concentrations of total N, exchangeable Ca, Mg and K were greater under forest soil, but the concentrations of available P were similar under all three ecosystems. The smaller organic carbon and nutrient content of plantation soil is mainly due to its more open organic matter and nutrient cycles and nutrient immobilization in the fast‐grow

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00796.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.The soil has been investigated at a long‐term experiment examining the silvicultural and site‐related effects of four tree species (Scots pine, Norway spruce, oak, common alder), planted pure or in mixtures. The experiment is located in Gisburn Forest, Yorkshire, and commenced in 1955. After 32 years, small significant differences were found for soil properties relating to soil organic matter accumulation and incorporation; the soil under the conifers and alder was slightly more acid than that under oak and grass control plots, and the conifers had thicker F and H but thinner A horizons. There was also some evidence that the conifers and alder has retarded the formation of a grey iron‐deficient B horizon. Some mixed plots were differentiated from pure ones by canonical variate analysis. Soil pH has declined under all plots since 1954; the effect of mixing species on this property is disc

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1990.tb00797.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY