Earthworms bring compacted and loose soil to a similar mechanical state

We tested the hypothesis that earthworms stabilise loose soil and loosen compacted soil to a similar mechanical state. Casts collected from initially loose soil (980 kg m⁻³) had 10-fold greater viscosity (31 kPa s) and 5-fold greater yield stress (200 Pa) than a control soil without worms. Lumbricus terrestris; Dendrobaena sp. and Aporrectodea longa were all investigated, with no difference found between species. In compacted soils (1300 kg m⁻³), A. longa produced casts with similar mechanical properties to loose soil, with viscosity and yield stress decreased by 45% compared to the control without worms. Earthworms were shown to bring initially loose and compacted soil to an intermediate mechanical state that is more favourable for structural stability and root growth.     

A comparison of microtubers and field-grown tubers of potato (Solanum tuberosum L.) for hexoses, sucrose and their ratios following postharvest cold storage

Cold-induced sweetening (CIS) is a significant postharvest problem in processing potato (Solanum tuberosum L.) tubers. A rise in hexose sugar levels during cold storage results in a brown, bitter tasting and unmarketable product. We tested if potato microtubers (MicroT) can undergo CIS and if this corresponds to the CIS response in field-grown tubers (FieldT) with the hope of fast-tracking breeding programmes using a MicroT system. Using MicroT from potato genotypes representing a range of CIS response levels we have demonstrated that MicroT undergo CIS more rapidly than FieldT. Correlations of glucose:sucrose and hexose:sucrose ratios were highly significant between the two tuber types after cold treatment and these ratios are known to be good predictors of invertase activity, a key regulator of CIS. Correlations of individual sugars were non-significant before and after postharvest cold treatment.     

Strong relationships between levels of puerulus settlement and recruited stock abundance in the red rock lobster (Jasus edwardsii) in New Zealand

Any demonstrable relationship between levels of settlement and subsequent strength of recruitment to the fishery is of great interest to the managers of rock lobster fisheries. A project to estimate levels of settlement of the puerulus stage of the red rock lobster, Jasus edwardsii, on crevice collectors around the main rock lobster fishing shores of New Zealand has been in place for more than quarter of a century, with considerable temporal variation but also strong temporal and spatial consistencies in settlement. There are significant correlations between settlement level and the fishery catch per unit effort (CPUE) response for most fishery areas, at time lags between settlement and recruitment consistent with what is known of juvenile growth rates. There are also significant correlations when more than one settlement year is correlated against each year of CPUE, to account for variable growth rates between individual lobsters. There was no concurrence between field and fishery model estimates of recruitment for the three fishery areas with sufficient data, revealing a different interpretation of annual rates of recruitment to the fishery between the two approaches. The reasons for the discrepancy are unclear, but one possibility is that the model estimates of recruitment are poor.     

Categorizing Rice Cultivars Based on Cluster Analysis of Amylose Content,Protein Content and Sensory Attributes

Presently, rice cultivars are categorized according to grain dimensions, amylose content, and alkali spreading value (gelatinization temperature type). Categorization of rice cultivars based on total sensory impact is needed. This work endeavors to divide world rices into groups based on amylose, protein, flavor, and texture properties. Ninety‐one rice samples representing 79 different cultivars and seven growing locations were separated into seven groups with Ward's Cluster Analysis. Cluster 1 included a third of the rice samples and had cultivars with a large diversity of grain shapes and amylose contents. Mean attribute scores for this cluster were near the grand mean for the collective rice samples for nearly every sensory attribute. Cluster 2 included conventional U.S. short‐ and medium‐grain cultivars. Cluster 3 included conventional U.S. medium cultivars that were produced in Louisiana. Mean sensory scores for this cluster characterized these cultivars as having relatively undesirable flavor and texture attributes. Cluster 4 included Japanese premium quality cultivars and U.S. medium‐grain cultivars developed for the Japanese market. Cluster 5 included high‐amylose, indica types that had relatively firm textural properties. Cluster 6 included relatively soft cooking, aromatic cultivars. Cluster 7 included waxy cultivars and other soft cooking grains. In several cases, the production environment (location, weather effects, etc.) influenced flavor and texture characteristics and resulted in the cultivar falling into an unexpected cluster. This categorization serves as a catalyst for indexing rice cultivars for cooking and processing qualities.     

Influence of drying and ageing on the stabilization of earthworm (Lumbricidae) casts

The influence of drying and ageing on the stabilization of casts produced by the endoge′ic earthworm, Aporrectodea rosea, from a soil, which was hard-setting and low in organic matter, were investigated in the laboratory. Casts and uningested soil were aged-most for up to 32 days, dried for up to 21 days, or subjected to different wetting and drying cycles over 30 days. The dispersion index of aged-moist casts decreased from 0.40 to 0.25 over 32 days, while dispersion index of dried casts decreased from 0.40 to 0.01 over 21 days. The dispersion index of air-dried casts was not significantly increased by five cycles of wetting and drying. The dispersion index of dried casts was not significantly less than that of dried soil. In soils wetter than a matric potential of approximately –35kPa, stabilization of casts was probably due to a combination of cohesion of soil particles, age-hardening and growth of microorganisms. However, in soils drier than –35kPa, cementation was probably the major mechanism of stabilization. The addition of wheat straw to the soil prior to ingestion by earthworms increased dispersion from aged-moist casts, but did not influence dispersion from dried casts. The addition of wheat straw decreased the number of air-dried casts which slaked severely. The concentration of soluble carbohydrate decreased with dispersion index as casts and uningested soil were each dried. This suggested that soluble carbohydrate may have been denatured with or without being bonded to soil particles during drying. Received: 7 May 1996     

Considerations for Scottish soil monitoring in the European context

Two contrasting phases of work are described that help inform the development and requirements of a soil monitoring system: firstly, the development and application of a multi-criterion analysis of soil quality indicators grounded in the basic natural sciences; and secondly, scrutiny of the outcome of that process by a wide range of non-specialist but key stakeholders at a workshop. This process ensures that the final monitoring design meets both the scientific rigour expected from a monitoring system and as far as possible meets the aspirations of policy and regulatory stakeholders. Individual indicators of soil quality were evaluated in terms of their applicability against a number of important environmental and logistical parameters and therefore their overall fitness for purpose. These included relevance to different soil types, functions, habitats and threats to soil, the inherent variability of soil, and a range of technical aspects such as analytical complexity, precision and reproducibility of analytical results and whether a standard operating procedure (SOP) existed for the technique. A tiered approach to soil monitoring was supported by workshop delegates. This will require indicators that are suitable and effective at national, site-specific and process-level scales. In addition, the opportunities for synchronizing soil monitoring with air and water quality monitoring should be considered and the potential for integrating on-site measurements with remote methods should be researched further. It was considered by workshop attendees that soil monitoring should be rooted in pedological principles (i.e. recognizing defined soil horizons) to ensure that results can be extrapolated from individual sites and to retain flexibility.