Spatial distribution of Lolium rigidum seedlings following seed dispersal by combine harvesters

Abstract

This paper considers the relationships between the dispersal of seeds and the distribution pattern of an annual weed. A comparative study of seed dispersal by combine harvesters, with and without a straw chopper attached, was established using Lolium rigidum, a common weed in Mediterranean cereal crops. Seed dispersal distance was quantified and the relationships between dispersal and fine-scale seedling distribution evaluated. Primary dispersal of L. rigidum seeds occurs in a very limited space around the parent plants, but the density of seed is low because most seeds do not fall from spikes spontaneously. In contrast, many seeds are spread by combine harvesters. In this study the maximum dispersal exceeded 18 m from established stands in cereal fields, although the modal distance was close to the origin. In addition, the action of the combine harvesters tended to accumulate L. rigidum seeds predominantly under the straw swath, with some lateral movement. This action could explain the fine-scale banded pattern of L. rigidum in cereal fields. Although the treatment of straw by the standard and straw chopper combines differed, the resultant seed distribution showed few differences.

Potential for seed-mediated gene flow in agroecosystems from transgenic safflower (Carthamus tinctorius L.) intended for plant molecular farming

“…Crop seed is a propagable material as well as a major commodity, and may be distributed locally and internationally (Saji et al 2005) with consequence to international trade. Volunteer populations of transgenic canola (oilseed rape, Brassica napus L.) have been found, initiated by seed spill during transport (Saji et al 2005;Yoshimura et al 2006) and weed and crop seed dispersal by farm machinery in and among fields is well documented (Blanco-Moreno et al 2004;Shirtliffe and Entz 2005;Barroso et al 2006). Seeds may germinate, producing volunteer plants and the seeds from these populations serve as secondary sources of gene flow (Yoshimura et al 2006).…”

Effects of relative emergence time and water deficit on the timing of fruit dispersal in Raphanus raphanistrum L.

“…Roth L.), and wild oat (Avena fatua L.) retain 85, 99, 77, and 84% of seeds until crop maturity, respectively (Walsh and Powles 2014). Seed retention of annual ryegrass (Lolium rigidum Gaudin L.) in Spanish wheat fields was even greater, with 96% seed retention at crop maturity (Blanco-Moreno et al 2004).…”

“…Seed banks allow weeds to persist through cropping phases and extend weed infestations (Fenner 1995). During the normal harvest of grain crops, retained weed seeds enter the harvester, are separated from the grain, and distributed over the field by the chaff-spreading system of the harvester (Barroso et al 2006;Blanco-Moreno et al 2004;Rew et al 1996;Shirtliffe and Entz 2005;Walsh and Powles 2007). Mechanisms targeting escaped weed seeds in the chaff fraction, such as HWSC systems, have been developed to either remove seeds via chaff carts or destroy seeds through seed destructors at crop harvest (Shirliffe and Entz 2005;Walsh et al 2012;Walsh and Newman 2007;Walsh and Powles 2007).…”

Cultural control of herbicide-resistant Lolium rigidum Gaud. populations in winter cereal in Northeastern Spain

“…Lolium rigidum plant density in the control plots was high in all cases (Table 1). Plots were placed perpendicular to the straw swaths, where this weed emerges predominantly (Blanco-Moreno et al, 2004) so that L. rigidum distribution was similar between plots.…”