摘要:

Abstract.Regression is frequently abused in soil research. Its proper use is for statistical prediction. It may also be used to calculate equations for calibration. A regression equation may be used to express a functional relation between two soil variables that are thought to be related by some simple mathematieal law but only where one of the variables is known exactly. In most other circumstances regression is inappropriate. Where departures from a functional relation are due to errors of measurement and sampling fluctuation it should be replaced by a structural analysis to find the best equation. Where the underlying relation is truly bivariate it should be described as such.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1989.tb00759.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.Graphs of soil pH against time were plotted for the Park Grass Experiment at Rothamsted Experimental Station, begun in 1856, and the Long‐term Liming Experiments at Rothamsted and Woburn farms, begun in 1962. These showed that the magnitude and duration of the effect of lime applications varied with soil type, initial pH, fertilizer nitrogen application, and the crop grown. Simple equations for each situation were linked to form an empirical model which, with appropriate input data for soil type, crop, and initial and target pH, predicted the lime needed to reach that pH. Model predictions compared well with estimates from a Woodruff‐type buffer method. The model forms a sound basis for a more comprehensive lime requirement model covering the whole of the United King

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1989.tb00760.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.A spoil and vegetation survey was conducted of five fields reclaimed from coal mine spoils seeded in different years at the Whitewood mines of south‐central Alberta, Canada. It aimed to understand the causes of visibly wide variations in ground cover of the seeded species which was mainly alfalfa. Sites were initially stratified into productivity classes: A (high), B (medium), and C (low) based on the seeded species, and then sampled. Cover and dry weight declined linearly with age of reclaimed field. The spoil at class‐A sites contained more clay than that of class‐C sites. It also contained more moisture and a better cover. Electrical conductivity (EC) and the concentrations of soluble B, Mg, Na, and K in the spoil were significantly greater at class‐C sites. Cover and dry weight of the seeded species were negatively correlated with EC, B, Mg, and Na in the spoil, thus implicating these factors in poor vegetative productivity, particularly in the dry conditions that typify this part of

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1989.tb00761.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.The measurement of the shear strength of the root plate/soil interface beneath mature trees is described. Results from this method are given for a total of 77 sample trees from crops of Sitka spruce aged between 24 and 35 years growing on a peaty gley, a deep peat and a brown earth. Shear strength was much higher for the brown earth than for either the peaty gley or the deep peat, mainly because there was a less clear‐cut boundary to the rooting depth compared with the rooting boundary caused by the high water table on the peat sites. There was a slightly higher shear strength for the peaty gley than for the deep peat, but no apparent difference in shear strength between the peat and the underlying mineral soil in the peaty gley. The shear strength measurements were consistent with observed differences in tree stability and the method of measuring shear strength aids the assessment of susceptibility of trees to windthro

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1989.tb00762.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.Following removal of the upper 40 cm of soil, the physical properties of the exposed B horizon of a red‐brown earth (Goulburn clay loam) were ameliorated using a combination of gypsum (5.4 ha−1) and rye grass. Phosphorus (P), nitrogen (N) and potassium (K) fertilizers were added to improve nutrient availability. The ameliorated properties of the exposed B horizon were compared with those of equivalent depths from an adjacent intact profile of Goulburn clay loam.Initially, during the establishment phase of the rye grass, the gypsum increased the electrolyte concentration in the 0–10 cm layer, and stabilized the soil surface against mechanical dispersion. After 18 months all the gypsum in the 0–10 cm layer had dissolved. However, in the presence of rye grass, the soil surface was no longer susceptible to dispersion by the mechanical impact of water. The rye grass improved soil physical properties mainly in the upper 20 cm of the exposed B horizon. Water‐stable aggregation>2000 μm and macroporosity increased, and bulk density and penetrometer resistance of the soil decreased.Continuous applications of P, N and K fertilizers resulted in a gradual improvement in the nutritional properties of the exposed B horizon. However, because of the large phosphorus adsorption by the exposed clay, 300 kg P ha−1was required to provide sufficient available phosphorus in the 0

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1989.tb00763.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.A model has been developed based on multiple regression which explains 95% of the variation in nitrate loading of the major rivers in the 4453 km2Lough Neagh catchment for the years 1971–1987. The model relates loading of nitrate in the hydrological year to fertilizer usage, previous summer rainfall, summer temperature of the current year and December‐May flow. It indicates that there is an increase in nitrate loading associated with fertilizer usage, and that the equivalent of 13% of nitrogen fertilizer that is lost as leachate comprises 50% of the river loadi

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1989.tb00764.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.The loess plateau in China is the most developed region of loess in the world in terms of extent, thickness and depositional sequence. It is also the region with the most serious soil erosion in the world. This paper reviews the factors and reasons for soil erosion in this area. The loess is prone to vertical cleavage and its surface soils are soft and loose. Rainstorms are frequent with intense rain concentrated during the summer. Irrational land use and exploitive management have been carried out for thousands of years and express themselves through the loss of grassland and natural forests. Finally, some soil conservation schemes for use in the loess plateau are suggested.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1989.tb00765.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract.This paper reviews research on sediment yields in British fresh waters affected by afforestation in their catchments. Soil erosion and sedimentation in fresh waters increase after afforestation in the uplands. In the long term a three‐to tour‐fold increase appears to be common in established upland forests, but much larger increases, some amounting to 50 times that before afforestation, have been recorded soon after ploughing, draining, roadmaking and harvesting. Some of the erosion has been exacerbated by environmental conditions such as steep slopes and storms. Improved silvicultural practices should reduce sediment output to fresh waters, but they might not prevent serious sedimentation following afforestation in the uplands. In contrast, afforestation of arable land under the Farm Woodland Scheme should result in decreased rates of erosion in the lowla

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1989.tb00766.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Book reviews in this article:Land resources in the Loess Plateau of ChinaEditor Professor Zhou Xianmo (S.M. Chou).

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1989.tb00767.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY