Soil temperature effects on emergence and survival of Iris lactea seedlings

Abstract

Iris lactea is a perennial herbaceous plant that is rapidly gaining popularity in gardens and for vegetation regeneration in its native northern China. However, its seeds have a high level of apparent dormancy with seedling emergence percentages being <5% under natural field conditions. An experiment was conducted to investigate the effects of soil temperature on seedling emergence. Treatments involved three soil cover mulches: (1) clear, colourless plastic film; (2) opaque, silvered plastic film; and (3) rice straw. The controls (4) were uncovered. The primary effect of the cover treatments was to increase soil temperature and seedling emergence significantly increased in response. The relatively high soil temperatures under the clear film increased seedling emergence to >60%. Increased soil temperatures not only raised emergence percentages but also shortened the emergence period. However, there were no significant differences in the soil thermal‐time requirements for seedling emergence. A second‐order polynomial function model was used to describe the correlation between seedling emergence and soil thermal time. The use of a clear film cover is recommended to protect I. lactea seedlings in early April, and to ensure better establishment and survival of the young plants before the onset of cold weather in the autumn.