Seed and microsite limitations to emergence of four annual weed species

Abstract

The emergence of annual species depends on the number of seeds present and the biotic and abiotic conditions directly surrounding those seeds (the microsite). A field experiment was conducted to study the relative importance of seed presence vs. microsite conditions in determining the emergence of four annual species. Green foxtail, wild mustard, wild oat, and canola were seeded at 200, 400, and 1,200 seeds m−2in separate plots in a coarse, loamy, mixed Typic Haplocryoll and a fine, mixed Typic Haplocryoll soil. Five microsite modification treatments (control, irrigation, soil compaction, soil compaction plus irrigation, and no crop) were applied to all weed seed density treatments for each weed species. All plots were seeded to spring wheat. Irrigation or soil compaction increased percent emergence of wild oat. Green foxtail emergence tended to increase with soil compaction in 2001 but not in 2002. Wild mustard and canola emergence were largely unaffected by microsite modification treatments. Weed emergence increased with increasing seed density for all species, but the proportion of the total number of seeds emerging decreased with increasing seed density for all species. We suggest that the emergence of the four weed species in this experiment was both seed and microsite limited. Increasing the number of seeds in the soil increased the probability of seeds landing within an appropriate microsite. For these four species, therefore, weed spread and weed patch formation may be determined both by seed production and dispersal and by variability in soil microsite conditions. Results suggest that weed management practices should limit seed dispersal of all species and discourage weed emergence of hard-to-control species during critical establishment periods.

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

“…The persistence and viability of crop seed in the seed bank is known to vary with the number of viable seeds in the soil and/or the seed microsite (i.e., depth of burial and soil moisture) (Cummings and Alexander 2002;Boyd and Van Acker 2004). Generally, annual crop seeds do not persist for long periods of time in soil (Cavers and Benoit 1989).…”

A trade off in the absolute magnitudes of seed and microsite limitations and their effects on population regulation

“…Seed and microsite limitations are of great importance for plant populations (Eriksson and Ehrlén , Boyd and Acker ). They reduce birth or increase mortality rates (Knight ), affecting population growth and size (Kollmann et al ).…”

Effect of planter and tractor wheels on row and inter-row weed populations

“…Boyd and Van Acker (2004) indicate that soil compaction occasionally increased the emergence of wild oat and green foxtail, but not wild mustard. Compacted soil can accumulate more growing degree days compared to undisturbed soil (Boyd and Van Acker, 2004) and thermal conductivity, heat capacity as well as thermal diffusivity all increase as the number of tractor passes increases from zero to three (Lipiec and Hatano, 2003). A single tractor pass will increase soil compaction by a degree that will depend on the physical properties of the soil and tire (Soane et al, 1981).…”