Stephen Nortcliff

Standardisation of soil quality attributes

An understanding of the nature of soils in natural and human influence ecosystems is essential if progress is to be made in the determination and monitoring of soil quality. This paper briefly discuss the changing circumstances which have resulted in the increased awareness of the importance of soil as a key component of both natural and human influenced environmental systems. These changed circumstances and the recognition of the often crucial role that soils play within these systems has resulted in a demand for measures of soil quality, similar to those used in the characterisation of water and air. Whilst it is relatively straightforward to quantify the fitness to breathe of air, or the fitness to drink with respect to water, it is considerably more difficult to identify similar criteria to be applied to soil. In part this arises because of the wide range of uses to which soils are put and in part because of the complexity of the soil system and the possibility that changes in the soil may be slow and possibly only occur when some threshold is reached. The paper stresses that any index of soil quality must consider soil function, and these functions are varied and often complex. A soil which is considered to be of high quality for one function may not be so for other functions. As a consequence there are potentially many soil properties which might serve as indicators of soil quality, and research is required to identify the most suitable. It may also be questioned whether it is appropriate to pursue this notion of a limited number of soil quality indicators. If an indicator is chosen comparisons between sites and results from different investigators are not possible unless the methods of analysis are given. Standard methods of soil analysis must be developed. These standard methods are distinct from national standard values, or indicator values frequently set by national governments or regulatory agencies. The International Standardisation Organisation (ISO) has developed a programme for the development of standard methods of soil analysis across a range of possible properties including visible, biological, physical and chemical properties. If it is decided that soil quality indicators are required and progress is to be made on developing acceptable indicators of soil quality with agreed standard methods of determination there is need for co-operation amongst soil scientists and those involved in determining appropriate and sustainable use of the soil.

Method for determining the acid ameliorating capacity of plant residue compost, urban waste compost, farmyard manure, and peat applied to tropical soils

Abstract Plant residue compost, urban waste compost, farmyard manure, and peat can be used to ameliorate soil acidity. The diversity of these materials and their highly variable composition mean that their reliability in increasing the soil pH is uncertain because of lack of a method to test their acid ameliorating capacities. Incubation of a Spodosol from Sumatra, an Oxisol from Burundi and an Ultisol from Cameroon with 1.5% by weight of four composts, a farmyard manure and a sedge peat resulted in increased soil pH and decreased aluminum (Al) saturation measured at 14 days of incubation. The increased soil pH was directly proportional to the protons consumption capacity of the organic materials. This was measured by titrating the organic material from their natural pH values down to pH 4.0. This measure of acid neutralizing capacity provides a simple test method that was reliable across the variety of materials used. The final pH of the soil treated with organic material can be predicted with reasonable...

Initial responses of maize and beans to decreased concentrations of monomeric inorganic aluminium with application of manure or tree prunings to an Oxisol in Burundi

Prunings of Calliandra calothyrsus, Grevillea robusta, Leucaena diversifolia and farm yard manure were applied each cropping season at 3 and 6 t dry matter ha−1 to an Oxisol in Burundi. The field plots also received basal applications of nitrogen (N), phosphorus (P) and potassium (K). Application of the tree prunings or farm yard manure decreased the concentration of monomeric inorganic aluminium (Al) in soil solution from 2.92 mg Al dm−3 in the control plots to 0.75 mg Al dm−3 in the plots receiving 6 t ha−1Calliandra prunings. The other organic materials also decreased the concentration of monomeric inorganic aluminium in the soil solution. The lowered Al concentration led to a corresponding decrease in the percentage Al saturation of the 0–10 cm soil layer from 80% to 68%. Grain yields of maize and beans were strongly inversely related to the percentage Al saturation of the soil. This confirms that soil acidity was the main constraint to maize and beans production. The yield improvement was mainly attributed to the ameliorating effects of the organic matter application on Al toxicity. The nutrient content had less effect presumably because of fertilizer use. In the best treatments, the yield of maize increased from 0.9 to 2.2 t ha−1 and the corresponding beans yield increased from 0.2 to 1.2 t ha−1. A C Borstlap Section editor

Biological and chemical assessments of zinc ageing in field soils

As zinc (Zn) is both an essential trace element and potential toxicant, the effects of Zn fixation in soil are of practical significance. Soil samples from four field sites amended with ZnSO(4) were used to investigate ageing of soluble Zn under field conditions over a 2-year period. Lability of Zn measured using (65)Zn radioisotope dilution showed a significant decrease over time and hence evidence of Zn fixation in three of the four soils. However, 0.01 M CaCl(2) extractions and toxicity measurements using a genetically modified lux-marked bacterial biosensor did not indicate a decrease in soluble/bioavailable Zn over time. This was attributed to the strong regulatory effect of abiotic properties such as pH on these latter measurements. These results also showed that Zn ageing occurred immediately after Zn spiking, emphasising the need to incubate freshly spiked soils before ecotoxicity assessments.

Measurement of the acid neutralizing capacity of agroforestry tree prunings added to tropical soils.

Laboratory incubation in the UK of an Oxisol from Burundi and an Ultisol from Cameroon with 3·1% by weight of prunings of young shoots of Calliandra calothyrsus, Cassia siamea, Flemingia congesta, Grevillea robusta, Gliricidia sepium, Leucaena diversifolia and Leucaena leucocephala resulted in increased soil pH and decreased exchangeable aluminium content. The greatest increase in pH and corresponding decrease in exchangeable aluminium occurred during the first 14 days of incubation and the decrease continued at a slower rate until 42 days incubation. The acid neutralizing effect decreased after 42 days but was still important at the last sampling time at 98 days. Polyphenol to nitrogen ratio was not well correlated with observed change in soil pH whereas the total base cation (calcium, magnesium and potassium) content proved to be a good predictor of these changes in the Ultisol, but not in the Oxisol. The proposed mechanism giving rise to acid neutralization is complexation of protons and aluminium by organic anions. The total base cation content of the prunings ranged from 0·94 to 2·25 mol c /kg and the buffer capacity of the Oxisol was 48 mmol OH − /pH/kg.

Soils of the Tropics

The conditions for soil development in the lowland tropics are described, in particular the soil-forming factors, climate, parent material, topography and organisms, and their interactions through time. Of particular importance is the climate of the lowland tropics, which has a major influence on the nature of soil development because of high temperatures and the duration of the periods when the soil is moist. The nature of the parent material is also a major determinant of the nature of the soil. Because soil development has taken place in much of the tropics over long time periods, the soils have distinctive characteristics. Soil-forming processes are described briefly, in particular the nature of the weathering of the inorganic fraction of the soil, and the removal of soluble materials in leaching and the translocation of materials in suspension. Typical soils developed in the humid and seasonally moist tropics are briefly described, and comparisons made between the two most widely used international soil classifications, Soil Taxonomy and World Reference Base for Soil Resources. Some of the other soils found within the tropics are briefly described.

Soil acidification: comparison of acid deposition from the atmosphere with inputs from the litter/soil organic layer

Abstract At three relatively unpolluted sites in beech ( Fagus sylvatica ) woodlands on the Chiltern Hills of southern England, measurements were made over one year of the amount and composition of precipitation, throughfall, stemflow, and drainage below the soil organic layer. At two sites the soils were acidic and at the third the soil contained calcium carbonate. Comparison was made between the soil acidification potential (A.P.) of throughfall calculated as (H + + 2NH 4 + ) and the A.P. of the drainage water from the soil organic layer calculated as the difference between the sum of cations and the sum of Cl − , SO 4 2− and NO 3 − , that is, as HCO 3 − + organic anions. In the two woodlands with acidic soil the A.P. of throughfall was 198 mmol c m −2 a −1 and that of the drainage water was 224 mmol c m −2 a −1 ; the corresponding figures for the woodland with calcareous soil were 176 and 511 mmol c m −2 a −1 . The increases in the drainage water are attributed mainly to organic anions in the acidic soils and bicarbonate in the calcareous soil. The relative importance of the components in throughfall and the organic anions in drainage from the soil organic layer is discussed in relation to soil acidification.

Experimental crop growing in Jordan to develop methodology for the identification of ancient crop irrigation

Abstract Crop irrigation has long been recognized as having been important for the evolution of social complexity in several parts of the world. Structural evidence for water management, as in the form of wells, ditches and dams, is often difficult to interpret and may be a poor indicator of past irrigation that may have had no need for such constructions. It would be of considerable value, therefore, to be able to infer past irrigation directly from archaeo-botanical remains, and especially the type of archaeo-botanical remains that are relatively abundant in the archaeological record, such as phytoliths. Building on the pioneering work of Rosen and Wiener (1994), this paper describes a crop-growing experiment designed to explore the impact of irrigation on the formation of phytoliths within cereals. If it can be shown that a systemic and consistent relationship exists between phytolith size, structure and the intensity of irrigation, and if various taphonomic and palaeoenvironmental processes can be controlled for, then the presence of past irrigation can feasibly be inferred from the phytoliths recovered from the archaeological record.

Issues of water supply and contemporary urban society: the case of Greater Amman, Jordan

Over the last two decades, Jordan has suffered a chronic water crisis, and is the tenth most water-scarce nation on Earth. Such water stress has been well illustrated in the case of Greater Amman, the capital, which has grown dramatically from a population of around 2000 in the 1920s, to 2.17 million today. One of the distinctive characteristics of the water supply regime of Greater Amman is that since 1987 it has been based on a system of rationing, with households receiving water once a week for various durations. Amman is highly polarized socio-economically, and by means of household surveys, both quantitative and qualitative, conducted in high- and low-income divisions of the city, a detailed empirical evaluation of the storage and use of water, the strategies used by households to manage water and overall satisfaction with water supply issues is provided in this paper, looking specifically at issues of social equity. The analysis demonstrates the social and economic costs of water rationing and consequent management to be high, as well as emphasizing that issues of water quality are of central importance to all consumers regardless of their socio-economic status within the city.

The dynamics of a tropical floodplain environment with reference to forest ecology

The present investigation seeks to illuminate the dynamics of subsurface flow and overland flow in floodplain environments of a small forested tropical catchment near Manaus, Amazonas. There are large areas of floodplain environments within the tropical forest of the region, and these environments play a crucial role in determining the overall dynamics of the catchments, both with respect to the water flow through them, but also the distribution and movement of fresh litter and partially decomposed organic matter on the floodplain. The dynamics of these floodplain environments are considered in relation to the variations in storage capacity, groundwater fluxes, and saturated overland flow, together with the magnitude and frequency of overbank flow from the stream and the contemporary morphology of the floodplain. The floodplain hydrology in these environments appears to have a far more substantial role in the overall stream hydrology than is normally considered to be the case. Consequently an understanding of floodplain dynamics may lead to more successful management of tropical catchments both in their natural forested state and when cleared. The results suggest that some revision of the conventional model of flood activity may be required.