Hektor: the largest highly elongated asteroid

New observations of Trojan asteroid 624, Hektor, in April 1979 establish that the high amplitude of the rotational light curve of this object is caused by its elongated shape and not by patches of dark and light albedo on opposing hemispheres. These observations confirm that Hektor is a very unusual object and are consistent with the hypothesis that it may be a compound asteroid formed when two Trojans of comparable size fell together-a rare fossilized example of a planetary accretion process.     

Comparison of soil phosphorus extraction methods regarding their suitability for organic farming systems

Background

Organic farmers frequently report sufficient yield levels despite low or even very low soil phosphorous (P) contents questioning the applicability of widely used laboratory methods for soil P testing for organic farming.

Aims

The aim of this study was to compare the validity of a broad range of different soil extraction methods on soils under organic management from South West Germany and to test the correlation of the measured soil P concentration with plant offtake.

Methods

Twenty-two soil samples of eight different organic farms were extracted with different solutions: (1) water, (2) CAL, (3) Olsen, (4) Mehlich 3, (5) Bray P1, (6) Bray P2, (7) NaOH+Na₂EDTA, and (8) total P. The results were then correlated with above ground plant P.

Results

Spearman's rank correlation coefficient (r_s) of correlations between above ground plant P and extractable soil P (Water-P, CAL-P, and Olsen-P [+active charcoal {+AC}]) determined with ICP-OES were strong (0.94, 0.90, and 0.93, respectively). Among the tested methods, above ground plant P showed a strong correlation with CAL-P as detected by ICP-OES (r_s = 0.90) and colorimetry (r_s = 0.91). The comparison of CAL-P data provided by farmers and CAL-P analyzed during this research showed discrepancies between the results.

Conclusions

The results of this study indicate that the CAL method can be used in organic farming despite a low extraction of organic P (P_org). Furthermore, it is recommended for farmers to take soil samples for analyses regularly and interpret changes in P in the long-term instead of interpreting individual samples.     

KNOWLEDGE MANAGEMENT FOR LAND DEGRADATION MONITORING AND ASSESSMENT: AN ANALYSIS OF CONTEMPORARY THINKING

It is increasingly recognised that land degradation monitoring and assessment can benefit from incorporating multiple sources of knowledge, using a variety of methods at different scales, including the perspectives of researchers, land managers and other stakeholders. However, the knowledge and methods required to achieve this are often dispersed across individuals and organisations at different levels and locations. Appropriate knowledge management mechanisms are therefore required to more efficiently harness these different sources of knowledge and facilitate their broader dissemination and application. This paper examines what knowledge is, how it is generated and explores how it may be stored, transferred and exchanged between knowledge producers and users before it is applied to monitor and assess land degradation at the local scale. It suggests that knowledge management can also benefit from the development of mechanisms that promote changes in understanding and efficient means of accessing and/or brokering knowledge. Broadly, these processes for knowledge management can (i) help identify and share good practices and build capacity for land degradation monitoring at different scales and in different contexts and (ii) create knowledge networks to share lessons learned and monitoring data among and between different stakeholders, scales and locations. Copyright © 2011 John Wiley & Sons, Ltd.