Germination of Exhumed Weed Seed in Nebraska

An experiment was initiated in 1970 and continued through 1979 by exhuming and germinating seed of 12 economic weed species buried beneath 23 cm of soil in eastern and western Nebraska. Loss in germination of exhumed seeds over years is mathematically characterized by the formula for the rectangular hyperbola, which represents many shapes of curves that have zero as their lower limit. Of the 12 weed species, only fall panicum (Panicum dichotomiflorum Michx.) and redroot pigweed (Amaranthus retroflexus L.) seed germination did not drop significantly over the 10-yr burial period. Germination of redroot pigweed seed was higher when buried in eastern Nebraska, but was higher for smooth groundcherry (Physalis subglabrata Mack&Bush.) and velvetleaf (Abutilon theophrasti Medic.) when buried in western Nebraska. Germination of the other nine species were not affected by burial location. The 12 weed species can be ranked as those showing most to least rapid loss of germination during burial for 10 yr as follows: honeyvine milkweed [Ampelamus albidus (Nutt.) Britt.], hemp dogbane (Apocynum cannabinum L.), kochia [Kochia scoparia (L.) Schrad.], sunflower (Helianthus annum L.), large crabgrass [Digitaria sanguinalis (L.) Scop.], common milkweed (Asclepias syriaca L.), musk thistle (Carduus nutans L.), velvetleaf, fall panicum, redroot pigweed, green foxtail [Setaria viridis (L.) Beauv.], and smooth groundcherry.