Nitrogen fixation by caucasian clover and white clover in irrigated ryegrass pastures

The N₂ fixation ability of caucasian clover was compared with that of white clover in irrigated ryegrass pastures over years 2 and 3 of a grazing experiment, using the ¹⁵N enrichment technique. ‘Endura’ caucasian clover was inoculated with the specific Rhizobium strain ICC148. The N concentration in clover herbage and the proportion of clover N derived from N₂ fixation (PN) were similar for both clovers at averages of 4.6%N and 50–60% respectively over the 2 years. The amount of N₂ fixed per hectare was directly related to the amount of clover dry matter (DM) produced by the two clover species. Caucasian clover produced four times the DM yield of white clover in year 2 (5400 cf. 1450 kg DM/ha) and four times the amount of N₂ fixed in herbage (136 cf. 36 kg N/ ha). In year 3, caucasian clover produced 50% more clover DM (3450 cf. 2370 kg DM/ha) and N₂ fixed (98 cf. 66 kg N/ha) than white clover. The increased N input from caucasian clover increased grass %N and N uptake from soil in caucasian clover pastures resulting in higher total pasture production compared with white clover pastures (15.7 cf. 14.2 t DM/ha) by year 3. In this study, caucasian clover demonstrated greater potential than white clover to meet the N demands of high-yielding perennial ryegrass in an intensive pastoral system.The authors acknowledge funding from the Struthers Trust for the development of the grazing experiment at Lincoln University and FRST funding for provision of ¹⁶N and N analyses. We thank the C. Alma Baker and Struthers Trusts for providing A.D. Black with financial support from post-graduate scholarships

Describing the where – improving image annotation and search through geography

Image retrieval, using either content or text-based techniques, does not match up to the current quality of standard text retrieval. One possible reason for this mismatch is the semantic gap – the terms by which images are indexed do not accord with those imagined by users querying image databases. In this paper we set out to describe how geography might help to index the where facet of the Pansofsky-Shatford matrix, which has previously been shown to accord well with the types of queries users make. We illustrate these ideas with existing (e.g. identifying place names associated with a set of coordinates) and novel (e.g. describing images using land cover data) techniques to describe images and contend that such methods will become central as increasing numbers of images become georeferenced

A theoretical grounding for semantic descriptions of place

This paper is motivated by the problem of how to provide better access to ever enlarging collections of digital images. The paper opens by examining the concept of place in geographic theory and suggests how it might provide a way of providing keywords suitable for indexing of images. The paper then focuses on the specific challenge of how places are described in natural language, drawing on previous research from the literature that has looked at eliciting geographical concepts related to so-called basic levels. The authors describe their own approach to eliciting such terms. This employs techniques to mine a database of descriptions of images that document the geography of the United Kingdom and compares the results with those found in the literature. The most four most frequent basic levels encountered in the database, based on fifty possible terms derived from the literature, were road, hill, river and village. In co-occurrence experiments terms describing the elements and qualities of basic levels showed a qualitative accordance with expectations for example, terms describing element of beaches included shingle and sand and, those for beach qualities included being soft and deserted

Eliciting concepts of place for text-based image retrieval

This paper describes research being employed in the Tripod project to improve the retrieval of photographs through a comprehensive knowledge of where they were taken. The methods described here attempt to elicit semantics, and thus terms for use in indexing, related to the idea of place from theoretical geography. Three approaches are outlined: literature-based, empirical experiments, and data mining

Describing place through user generated content

Geographically referenced user generated content provides us with an opportunity to, for the first time, gather perspectives on place over large areas by exploring how very many people describe information. We present a framework for analysing large collections of user generated content. This involves classification of descriptive terms attached by users to photographs into facets of elements, qualities, and activities. We apply this framework to two contrasting photographic archives — Flickr and Geograph, representing weakly and strongly moderated content respectively. We propose a method for removing user-generated bias from such collections though the user of term profiles that can assess the effect of the most and least prolific contributors to a collection. Analysis and visualization of co–occurrence between terms suggests clear differences in the description of place between the two collections, both in terms of the facets used and their geographical footprints. This is attributed to the role of moderation/editorialising of content; to the role tags and free–text has on descriptive behaviour and on the geographic footprint of content supplied to the two collections

Nitrogen fixation by caucasian clover and white clover in irrigated ryegrass pastures

The N₂ fixation ability of caucasian clover was compared with that of white clover in irrigated ryegrass pastures over years 2 and 3 of a grazing experiment, using the ¹⁵N enrichment technique. ‘Endura’ caucasian clover was inoculated with the specific Rhizobium strain ICC148. The N concentration in clover herbage and the proportion of clover N derived from N₂ fixation (PN) were similar for both clovers at averages of 4.6%N and 50–60% respectively over the 2 years. The amount of N₂ fixed per hectare was directly related to the amount of clover dry matter (DM) produced by the two clover species. Caucasian clover produced four times the DM yield of white clover in year 2 (5400 cf. 1450 kg DM/ha) and four times the amount of N₂ fixed in herbage (136 cf. 36 kg N/ ha). In year 3, caucasian clover produced 50% more clover DM (3450 cf. 2370 kg DM/ha) and N₂ fixed (98 cf. 66 kg N/ha) than white clover. The increased N input from caucasian clover increased grass %N and N uptake from soil in caucasian clover pastures resulting in higher total pasture production compared with white clover pastures (15.7 cf. 14.2 t DM/ha) by year 3. In this study, caucasian clover demonstrated greater potential than white clover to meet the N demands of high-yielding perennial ryegrass in an intensive pastoral system.The authors acknowledge funding from the Struthers Trust for the development of the grazing experiment at Lincoln University and FRST funding for provision of ¹⁶N and N analyses. We thank the C. Alma Baker and Struthers Trusts for providing A.D. Black with financial support from post-graduate scholarships