Effects of Tillage and Mulch on the Emergence and Survival of Weeds in Sweet Corn

Abstract

1. The effects of tillage and non-tillage combined with no mulch and rye (Secale cereale) mulch on the emergence and survival of weeds in sweet corn (Zea mays) are reported. 2. The four most abundant weed species (Amaranthus retroflexus, Chenopodium album, Portulaca oleracea, and Digitaria sanguinalis) showed significantly lower emergence in till than in no-till treatments at one or more census times, probably because of seed burial and greater seed mortality in the till treatments. 3. Taraxacum officinale did not show lower emergence rates in till than in no-till, probably because of the short time between seed dispersal and germination. 4. Survival of Amaranthus was significantly greater in no-till than in till treatments, with the difference most pronounced late in the growing season. 5. The presence of corn or corn and rye mulch significantly reduced weed emergence for all species at one or more censuses. 6. Rye, killed with herbicide and used as a mulch, slightly decreased emergence and had no effect on survival. 7. A procedure for testing for departure of a survivorship curve from a truncated negative exponential is presented. Survival of annuals and other monocarpic plants should be considered truncated by successful reproduction. 8. In the absence of herbicides, mortality rates for Amaranthus and Chenopodium declined as the plants grew to maturity. 9. In most treatments, late-emerging plants survived to maturity better than earlier emerging plants, possibly because of shorter exposure to mortality factors. In the absence of herbicides, very dense stands of weeds led to greater mortality of later emerging cohorts.