Experiments on germination and emergence of velvetleaf seeds were carried out in order to clarify their emergence characteristics in arable land in Japan.
1) In seeds stored under room conditions, breaking of primary dormancy was promoted at a low temperature (5°C). The primary dormancy was also broken after 3 months of storage at a high temperature (25°C) under both laboratory and field conditions. These findings suggested that breaking of the primary dormancy of velvetleaf seeds proceeded under natural conditions in the fall (Fig. 1).
2) The optimum temperature for germination of freshly harvested seeds was 30°C. Alternate temperatures and light conditions enhanced the germination (Table 1). After storage for one year under dry conditions, the temperature range suitable for seed germination expanded, and promotive effect of light on germination was lost (Table 1).
3) Seedlings of velvetleaf tended to emerge uniformly from the seeds buried within a depth of 5cm in the soil (Fig. 3 and Table 2).
4) Weight of seeds was smaller for those set in capsules at the upper position in the plant. Emergence percentage decreased with the decrease in the seed weight (Table 3 and Fig. 4).

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In hilly land of the Loess Plateau in China, bare ground has expanded due to crop cultivation and overgrazing. Field experiments were carried out to analyse the vegetation, soil loss and surface runoff and to identify perennial gramineous plants for vegetation recovery in the degraded southern slope. As a result of the prohibition of cultivation and grazing by sheep during twenty five years, dominant species changed from annual herbs to perennial herbs, the vegetation cover rate increased, and the amount of soil loss and surface runoff decreased. Plantation of switchgrass (Panicum virgatum) during six years reduced soil loss and surface runoff remarkably. One hundred fifty nine perennial weed species were introduced from foreign countries, and twenty species among these weeds such as smooth bromegrass (Bromus inermis) and switchgrass have grown very well.

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