A weed suppressive index for spring barley ( Hordeum vulgare) varieties.

A screening programme for crop variety competitiveness would ideally be based on only a few, non-destructive measurements of key growth traits. In this study we measured the weed suppressive ability of 79 varieties of spring barley in two ways: (i) directly, by weed coverage assessments under weedy conditions at three Danish locations in 2002–2004 and (ii) indirectly, by non-destructive measurements of varietal growth traits under weed-free conditions in 17 other experiments in Denmark in 2001–2003. Based on just four varietal growth traits (reflectance, leaf area index, leaf angle and culm length), we successfully developed a method for indexing the weed suppressive ability of spring barley varieties. The suppressive index ranged from 12% in Lux and 55% in Modena in proportion to the 90% quantile coverage of all varieties. The index was validated against independent data from two locations in 2005 with 14 and 24 varieties and was found valuable for future use in regular screening programmes. [ABSTRACT FROM AUTHOR]