Weed Competition Effects on Growth and Yield of Spring-Sown White Lupine

Abstract

White lupine (Lupinus albus L.) is an annual legume that is grown for both seeds and green biomass, but several agronomic aspects of this crop, including response to weed competition, have not been studied extensively. Field experiments over two growing seasons (2012 and 2016) were carried out in Orestiada, Greece, to study the growth and development of spring-sown white lupine under season-long weed competition from natural weed flora compared with its growth without weed competition. Treatments were arranged in a randomized complete block design with four replications and included (i) a non-treated (weedy) control, where weeds (Chenopodium album and Sorghum halepense) remained in the plots throughout the experiments and (ii) a weed-free control, where weeds were removed upon crop emergence and the plots were kept free of weeds throughout the experiments by hand removal. The presence of Chenopodium album and Sorghum halepense reduced the aboveground dry matter accumulation of white lupine ‘Multitalia’ at 7 weeks after crop emergence by 18.0% in the first growing season and 29.5% in the second growing season, while the corresponding decrease in the aboveground dry matter accumulation at 9 weeks after crop emergence was 25.3 and 33.4%. However, the reduction in dry matter accumulation was limited to lower levels after flowering (9.9% in the first and 12.8% in the second growing season). In both growing seasons, values of the ability to withstand competition (AWC) index were lower at 7 and 9 weeks from crop emergence than at maturity. Seed yields were 1.58 Mg per ha under weedy conditions and 2.20 Mg per ha under weed free conditions in the first growing season, and 1.59 and 2.32 Mg per ha, respectively, in the second growing season. The values of the relative yield loss (RYL) index for seed yield were 28.2% in the first growing season and 31.5% in the second growing season. Overall, white lupine growth and seed yield was significantly affected by the occurrence of weeds mostly at the early vegetative stages, resulting in the potential yield not being achieved due to weed competition. Future research on weed competition across several sites and years would be useful to define more clearly the critical period of weed control in white lupine.