General scaling rules of the hysteretic water retention function based on Mualem's domain theory

Based on the domain theory of hysteresis, the present study rigorously derives a unified scaling transformation for predicting the wetting scanning retention function, θ_w ( ψ ), following any sequence of wetting and drying processes, from the measured main wetting curve. It is proved theoretically that a shape-similarity exists among the different wetting curves of a given soil. Each wetting scanning curve and the main wetting curve are described by the same normalized equation, over the common interval of ψ values. This shape-similarity is a direct result of the Mualem domain theory. On this basis, a general unique equation is formulated for prediction of all wetting scanning curves, of all orders, which is compatible with the Mualem dependent, as well as independent, domain theory. On the same theoretical basis, it is proved that no similarity exists among the drying scanning curves. Thus, the use of the scaling transformation for prediction of the drying scans is subjected to inconsistency with the physical principles underlying the dependent domain theory. As a result, scaling in this case would inevitably lead to inaccuracies in the calculated drying curves. A significant step forward has been made in the present study, from Mualem's dependent domain model (1984) with its implicit predictive formulae of the drying scanning curves. A unique explicit equation was theoretically derived, applicable for describing the drying scanning curves of all orders. This unique equation of the drying scanning curves, together with the general single equation of the wetting scanning curves, provided closure of all theoretical wetting and drying scans within the main hysteresis loop. Consequently, the retention function following any sequence of successive wetting and drying processes can be predicted by these two equations determined by the measured boundary curves.     

Farmland degradation in the mountains of Nepal: a study of watersheds ‘with’ and ‘without’ external intervention

Amidst growing concerns about farmlands conservation, this paper examines the status of farmlands in two mountain watersheds ‘with’ and ‘without’ external intervention, located in the western hills of Nepal. Information was obtained from a household survey and group discussions conducted during April to September 1999. The severity of soil erosion from farmers' perspectives, density of landslides, soil nutrient balance and change in crop yield have been adopted as indicators of the status of the land. Results of the analysis indicate that land resources in both watersheds are undergoing degradation, though the causes and extent of degradation vary from one type of land to another. Upland crop terraces, locally called bari, are undergoing degradation most seriously under the combined influence of severe soil erosion, landslide and the depletion of soil nutrients. In particular, soil erosion has severely affected nearly half of the upland crop terraces in both watersheds due to a number of natural and anthropogenic factors ranging from weak geological structure to arable agriculture. Landslide and nutrient depletion have affected all types of farmlands except homesteads in both watersheds. Overall, the extent and intensity of land degradation is relatively high in the non‐project area, as farmers were not provided with necessary technical and financial support. A broad strategy has been outlined for effective conservation of farmlands. Copyright © 2002 John Wiley & Sons, Ltd.     

Estimation of soil water retention function based on asymmetry between particle‐ and pore‐size distributions

By examining the symmetry between the distributions of particle‐size (PSD) and pore‐size (POD) in a soil, as hypothesized by early pore‐solid fractal (PSF) models, we found significant discrepancies in fractal dimensions between the PSD and the water retention curve (WRC) of a soil. Therefore, we developed an asymmetry‐based PSF model to estimate better the WRC directly from the PSD data of a soil. To do so, we adopted the concept of a microscopic arrangement of different‐sized particles to address such asymmetry, and evaluated the performance of the modified PSF model on five soil textural classes (coarse‐, moderately coarse‐, medium‐, moderately fine‐ and fine‐textured soils) using experimental PSD and WRC data from the UNSODA database (159 undisturbed soils for model calibration and 70 undisturbed soils for model validation). The fit of the symmetry‐based PSF model to the calibration dataset showed that the fractal dimension of the WRC (D_p) was slightly larger than that of cumulative mass distribution of particles (D_s) for most soils. The asymmetry‐based PSF model performed better than the symmetry‐based PSF model. In addition, the asymmetry‐based PSF model reduced the tendency to under estimate soil water content for a given matric head and the performance of the asymmetry‐based model was consistent irrespective of soil texture, indicating that the adoption of asymmetry between the PSD and the POD was adequate in predicting the WRC of a porous, particulate system such as soil.     

Influence of Malting on the Protein Composition of Spelt (Triticum spelta L.) ‘Frankenkorn’

Although spelt has promising aptitudes for beer and beverage production, almost no investigation about its protein modifications during malting has been conducted. Spelt proteins during the malting process were separated and analyzed, first, according to the isoelectric point and molecular weight (MW) and, second, according to solubility and MW. Moreover, the composition of the free amino acid was determined. Spelt proteins could be divided into a total of 13 zones according to their isoelectric point and MW. Most of the present proteins (90%) had a MW between 35,000 and 60,000 and an isoelectric point between 5.84 and 9.52. The most prominent protein fraction was defined by an isoelectric point between 5.84 and 6.89 and a MW between 35,000 and 55,000. Generally, a protein degradation process during malting was found. The Osborne fractionation revealed an albumin band pattern between 14,000 and 131,700, globulin ranging from 13,400 to 130,500, gliadin from 14,500 to 220,800, and glutenin from 19,800 to 215,300. The free amino acid composition increased in concentration except for asparagine, which decreased during malting. This paper contributes to the understanding of the protein modifications and metabolic changes during the malting process of spelt and facilitates the determination of the potential of this cereal for the production of cereal‐based products.     

Measuring interlayer potassium release rates from soil materials. II. A percolation procedure to study the influence of the variable ‘solute K’ in the < 1…10 μM range

Release rates of nonexchangeable K from Ap material of a Luvisol (‘Eckerde’ loess, 15% clay) are determined using a percolation procedure which avoids the common artifacts due to shaking or stirring soil suspensions and thus provides less biased kinetic data. CaCl₂ solution (10 mM_c. 20 °C. pH 5.8) is percolated through packages of soil aggregates (0.5–1 mm grain size, 0.5 g samples) with 0.02 to 25 ml h^?1. Solute K (C_K) was varied between < 1 and > 10 μM and is shown to have a dominant influence on the rates of interlayer K release. These increase exponentially below 3.5 μM (no steady state but steady decrease of release rates in each sample). The difference between the related C_K between moderate and high release rates is as small as 1 μM K. The average rates, of a 10-day-interval, starting after 1.3 times the exchangeable K had been removed, are 40 μmol K kg^?1 soil d^?1 at 4 μM C_K and 240 μmol kg^?1 d^?1 at 3 μM C_K, respectively. It is concluded that larger quantities of interlayer K become plant available in the studied soil if the of soil solutions gets below 3.5 μM (for 10 mM_c Ca, 20 °C, pH 5.8), probably because the dominant dioctahedral illites start to join the release process below this critical limit. The higher K concentration range was accounted for by K-Ca exchange isotherms which, by alteration of shape, indicate that K_nex release becomes measurable below 10 to 20 μM K. It is further argued that existing diffusion or reaction kinetics approaches towards K release are incomplete because the influence of solute K is not considered.     

Degradation of ‘reclaimed’ lands previously disturbed by coal mining in Wales: Causes and remedies

Large tracts of land, officially described as ‘reclaimed’ from former mineral workings, are in poor condition. Problems include gullying, soil erosion, soil compaction, accelerated run-off and poor vegetation cover. Some of these problems are caused by low quality and inappropriate engineering. Some are due to poor land husbandry. There is a need for a national system of quality control inspection for land reclamation sites and provision for training in the special problems of managing reclaimed lands. However, many further problems result from natural soil-forming processes, notably the accelerated breakdown of newly exposed minestones. This chokes the soils with fine particles, decreasing permeability and increasing bulk density. Current research directed to correcting this problem uses trees to build new self-sustaining soils from the ground up and to promote the development of a large and active community of soil organisms. It is hoped that the polysaccharide secretions of these organisms will bind the newly created clays into stable soil aggregates.     

Solar UV-B dosimetry in situ with ‘D-dosimeter’: effect of ozone depletion on the Vitamin D synthetic capacity of sunlight

Vitamin D synthesis under solar UV-B radiation (280–315 nm) occurs widely in nature being an inherent characteristic of mammals and plants. Current data suggest that pro-Vitamin D can act as an UV-B receptor in plants, and thus monitoring the Vitamin D synthetic capacity of sunlight should be the subject of UV-B dosimetry. With this aim ‘D-dosimeter’ based on an in vitro model of Vitamin D synthesis has been designed for direct monitoring the Vitamin D synthetic capacity of sunlight in situ. Besides, ‘D-dosimeter’ possesses spectral selectivity that is helpful for detecting mid-latitude UV-B trends which accuracy is hindered by variations of solar UV radiation by clouds and aerosols, that have a comparable effect on UV-B caused by variations in stratospheric ozone.     

The role of social capital in the promotion of conservation farming: the case of ‘landcare’ in the Southern Philippines

‘Social capital’ refers to the relationships of trust, communication, and cooperation that facilitate collective action in a community. It is particularly relevant to soil conservation in developing countries, which requires collective efforts to raise awareness of soil degradation, provide effective training in soil conservation practices, and implement soil conservation measures on individual farms. The Landcare Program in the Southern Philippines promotes simple conservation practices in upland environments through establishing and supporting community landcare groups and municipal landcare associations, thus augmenting the social capital of farmers in these locations. An evaluation of the Landcare Program in Barangay Ned, South Cotabato, based on a survey of 313 farm households and case studies of nine landcare groups, shows that, despite extreme isolation and difficult working conditions, farmers responded by rapidly forming landcare groups and a landcare association, and adopting contour barriers on their maize farms. They utilized the bonding social capital inhering in their local communities to build stocks of bridging social capital, linking them to information, training and resources from outside their immediate locality. A logistic regression model of the factors affecting adoption of contour barriers shows that farmers who had undergone the practical, farmer‐based training provided by the Landcare Program, and who were members of a landcare group, were significantly more likely to adopt conservation measures. These results confirm the value of investing in social capital to promote soil conservation. Copyright © 2005 John Wiley & Sons, Ltd.