Germination, emergence, and seed persistence of Panicum miliaceum L.

Abstract

The effects of varying levels of temperature, moisture, and seed depth on wild proso millet (Panicum miliaceum L.) emergence were observed. The effects of depth and duration of seed burial and the effects of seed overwintering on the soil surface on modes of seed depletion and persistence were studied. Patterns of wild proso millet emergence in the field were studied under conditions of plus or minus intraspecific and corn competition, and with and without soil disturbance. Emergence occurred over a range of 10 to 40 C with percent and speed of emergence increasing with temperature. Under simulated drought conditions induced by polyethylene glycol, germination was reduced at both temperatures tested (25, 30 C) as moisture stress increased. The greatest moisture stress that germination occurred at was -14 bars (1 .5%) at 30 C and -10 bars (2%) at 25 C. Germination at 30 C was higher at all moisture levels than at 25 C. Emergence from soil moisture levels of 35 to 100% field capacity was greater than 87%. Emergence ceased below 25% field capacity. Fluctuations of soil moisture resulted in slightly higher emergence than at a constant soil moisture level. Emergence was equal from 1 to 8 cm of seed depth with 14 cm the maximum depth of emergence. After 21 months of seed burial loss was greatest at 5 cm, with only 23% viable seed remaining. Persistence increased with soil depth with 77 and 93% viable seed at 10 and 30 cm, respectively. The main mode of depletion was in situ germination which decreased with depth. Seed death was not a major factor of depletion and was not affected by depth. The majority of depletion occurred within the first 12 months with seed populations stabilizing from 12 to 21 months of burial. Seeds overwintering on the soil surface were not greatly affected with more than 96% remaining viable seed. With high soil moisture, emergence patterns were influenced by fluctuations in temperatures in late May when emergence began, to June. In July and early August when emergence ceased, soil moisture became the limiting factor. Total emergence was greatest when all competition was removed. Both intraspecific and corn competition reduced emergence in July and early August. Cultivation acted to remove competition resulting in greater total emergence than treatments with competition.