Environmental influences on germination of utricles and seedling establishment of 'immigrant' forage kochia

Abstract

Establishment of forage kochia (Kochia prostrata subsp. virestens) stands from planting utricles has been erratic in the northern Great Basin. This study evaluated the effect of different seedbed environments varied by planting date on germination of utricles and seedling establishment. Utricles harvested in 1986 were planted on tilled seedbeds in late fall, winter, early and late spring 1986-87, and late fall, winter, and early spring 1987-88. Soils are fine-loamy, mixed, mesic, Xerollic Haplargids underlain by coarse gravel at a depth of 1.5 m. Utricles were broadcast at 400 pure live utricles/m2 in 2 by 2-m plots replicated 5 times. Additionally, nylon bags containing utricles were placed on the soil surface during planting, and on each subsequent planting date, bags of utricles were retrieved for germination trials. Seedling establishment was improved 85% (p<0.05) when utricles were planted in late fall and winter compared to spring of both 1987 and 1988. Utricles imbibed moisture when incubated in the field from late fall to winter and late fall to early spring 1986-87. When collected in winter 1987, imbibed utricles germinated 7 to 12 days faster (p<0.05) than dry controls, and those collected in early spring germinated 4 to 7 days faster (P<0.05) than controls. Total germination of utricles declined 9 to 2% with an additional year of storage in the laboratory. Utricles incubated in the field from late fall to winter and late fall to early spring 1987-88 germinated about 1.5 days faster (P<0.05) than controls when collected in winter and early spring 1988. These findings show why better seedling establishment can be expected from planting freshly harvested forage kochia utricles in late fall and winter before the soil surface begins to dry than in early and late spring in the northern sagebrush (Artemisia) steppe.