Echinochloa compensates seedling losses by increased biomass production

Abstract

Echinochloa crus-galli (L.) P. Beauv. (barnyardgrass) is a widespread weed in maize cultivation. Herbicide application at seedling stage is a common weed management practice. The aims of this study are: i) can E. crusgalli compensate variations in plant density by increased per plant biomass, ii) the influence of early and late emergence on biomass of plants and iii) the influence of seed predators on plant biomass.
In summer 2014 seeds of barnyardgrass were seeded in four densities in maize fields. Half of the plots were protected from seed predators by plastic frames. In 2015 emerging seedlings were marked in accordance to their germination period. That leads to six cohorts in autumn 2015. Seed producing plants of these cohorts were harvested and mean biomass per plant was estimated.
Lower plant numbers had a minor impact on biomass per area. A linear mixed model indicated that low plant densities were compensated by higher biomass per plant. High seed densities and late germination periods reduced the maximum biomass per plant but did not alter the undercompensating trend in biomass per plant density. Loss of seeds by seed predators led to small increases in plant biomass.
Results indicate the existence of a species specific pattern that needs to be integrated into weed management strategies.