Competition between six spring barley (Hordeum vulgare ssp vulgare L.) cultivars and two weed flora in relation to interception of photosynthetic active radiation

The aim of the study was to characterize the crop responses of six contrasting barley (Hordeum vulgare ssp. vulgare L.) cultivars and their weed suppression ability on two different weed flora, a natural weed flora and a Sinapis alba (L.) weed flora, and also to characterize the development of light interception profiles over time of the barley cultivars. One field experiment was conducted each year from 1997 to 1999 in an organic farming system SE of Uppsala, Sweden. The experiment included weed free stands and weed stands, as well as crop-weed stands. Differences between weed suppression ability of the cultivars was consistent over years and the two different weed flora. Cultivar Svani was the most competitive cultivar, followed by Filippa. The most competitive cultivars were also the cultivars that transmitted least PAR through the canopy. The differences between cultivars in penetration of light through the canopy were most apparent during the tillering and stem elongation stage at the soil surface and at the 20 cm canopy height. At the stem elongation stage, the most competitive cultivars had higher numbers of internodes compared with the least competitive cultivars. One of the most competitive cultivars, Svani, and one of the least competitive cultivars, Etna, showed the highest grain yield on average over weed flora and year. These results indicate that breeding for barley cultivars with both high competitive ability against weeds and high yielding ability would be possible.