The effect of spring barley (Hordeum vulgare L.) sowing rate on the dynamics of crop weediness at different development stages

Abstract

The experiment was carried out during the period 2004-2006 at the Lithuanian University of Agriculture's Experimental Station. Spring barley 'Aura" was sown at 0, 120, 200 and 280 kg ha' seed rates (0, 2.7, 4.5, and 6.2 million seeds ha"1). Dynamics of weediness was established having assessed weed density and species composition in a spring barley crop at the beginning and end of tillering, at booting, heading, milk and hard maturity stages. The number of weed species varied between 20 and 27. The prevalent weeds in the spring barley crop were annuals Chenopodium album L., Stellaria media (L.) Vill. and Erysimum cheiranthoides L., while perennials Sonchus arvensis L., Cirsium arvense (L.) Scop, and Equisetum arvense L. were in the minority. At the beginning of the growing season, from the beginning to the end of spring barley tillering, the number of weeds increased from 150-169 m2, 245-332 m2, 14-19 m2 to 169-171 m2, 310-37 m2 and 60-73 m2 in 2004, 2005 and 2006, respectively. At later growth stages, weed density consistently declined to 66-75 m2 in 2004, 166-204 m2 in 2005 and 44-62 m2 in 2006, except for the lowest seed rate crop in 2006, where weed density increased to 88 m2 in spring barley at hard maturity stage. With increasing seed rate (up to 280 kg ha4) and crop density, weed density consistently decreased to 28.2% and 49.8%, compared with the lower seed rates 120 kg ha-1 and 200 kg ha1. Spring barley seed rate did not have any significant influence on the spread of perennial weeds. In the crop-free soil, formation of weediness was in conformity with spring barley crop weed density dynamics, only was characterized by a higher number of weeds (to 458 weeds m2) which naturally filled in the vacant ecological niches in a field. At the end of spring barley growing season, in the crop-free plots, the number of perennial weeds was up to 10-fold higher compared with any of the crop densities tested.