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

Abstract

Summary 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.

Yield losses of soybean and maize by competition with interseeded cover crops and weeds in organic-based cropping systems

“…Other indexes were also used for measuring weed suppressive ability of crops (Hansen et al, 2008;Linares et al, 2008). These studies, however, focused mainly on the relationships between two plant species (i.e.…”

Effects of inter-varietal diversity, biotic stresses and environmental productivity on grain yield of spring barley variety mixtures

“…Hence, the 'organic' systems comprised trials with or without undersown grass clover mixtures, the former with no nutrients added and the latter with a reduced rate of manure and a weed harrowing strategy including one pre-emergence weed harrowing and 1-3 rounds of postemergence weed harrowing to keep weed pressures manageable (see Hansen et al 2008). Fungicides were not applied in any trial.…”

“…These included index values for grain yield potential, susceptibility towards each of the four prevailing foliar diseases: powdery mildew (Blumeria graminis), leaf rust (Puccinia hordei), net blotch (Pyrenophora teres), and scald (Rhynchosporium secalis), and straw length potential measured under weed and disease free conditions. In addition, values on the potential weed suppressiveness (%) were obtained from Hansen et al (2008), describing the average reduction in weed coverage in the plots of each variety compared to the 90% quantile based on all single-plot observations of that study. A number of variety characteristics were observed in the studied environments, of which eight corresponded to the assessed a priori characteristics: harvested grain yield (at 85% dry matter), disease severity of each of the four prevailing foliar diseases (in % leaf area infected), infestation by tall annual weeds and creeping weeds, respectively (each in % ground cover; see Østergård et al 2008), as well as straw length (after flowering, in cm).…”

Predicting spring barley yield from variety-specific yield potential, disease resistance and straw length, and from environment-specific disease loads and weed pressure

“…Competitiveness against weeds can be looked at in two ways: either as the ability of a crop to maintain the yield in the presence of weeds (tolerance to competition ;Goldberg 1990) or as the ability to reduce weed growth (suppression of competitors ;Tilman 1990). The former is most related to studies of yield loss whereas the latter is more relevant in relation to direct effects on the weeds (Hansen et al 2008). Straw length has been shown to be the most important factor for weed suppressive ability and also indirectly for minimising yield loss in the presence of weeds (Lemerle et al 1995).…”