|Abstract or Summary
- The effects of soil moisture (-2 to -17 bars), temperature (5 to 20°C), bulk density (0.90 to 1.40 gm/cm³) and texture (Bashaw silty clay and Woodburn silt loam) on germination and seedling emergence of three varieties (Yamhill, Bezostaya, Kirac 66) of wheat (Triticum Aestivum, L.) were evaluated under laboratory and field conditions. Experiments include: 1) germination of three wheat varieties in osmotic solutions made from Carbowax 6000 to evaluate the effect of osmotic potential and temperature oi germination, 2) measurement of seedling emergence for three wheat varieties in Bashaw and Woodburn soils as influenced by soil water potential and temperature, 3) measurement of seedling emergence for the three varieties at three planting dates to test the applicability of the laboratory response to field conditions, and 4) measurement of seedling emergence of Kirac 66 as affected by bulk density and soil water potential in Bashaw and Woodburn soils. The effect of seed protein content on germination and emergence was evaluated by using high and low protein samples (16.50 and 7.75 percent, respectively) of Yamhill wheat in the first three experiments. The number of days required to obtain 50 and 80 percent germination in osmotic solutions and seedling emergence in soil was significantly increased by lowering either temperature or water potential. Although significant interactions were measured, temperature affected germination more than water potential. There was a significant difference in the germination and emergence times of Yamhill, Bezostaya and Kirac 66. Kirac 66 emerged the fastest while Bezostaya consistantly emerged the slowest. Seed protein did not affect germination or seedling emergence of Yamhill variety. Models were developed using linear regression analysis for the laboratory seedling emergence study to predict the number of days required to obtain 50 and 80 percent emergence in Woodburn soil and 50 percent in Bashaw soil as a function of soil water potential and soil temperature. Since the response to the variables were similar, the models were composite for the three varieties. The models were used to determine soil water potential and temperature combinations which permit emergence to occur within a specified time. Soil texture and bulk density significantly affected the time required for seedling emergence. More days were required to obtain seedling emergence in Bashaw silty clay than in Woodburn silt loam soil at given soil water potential primarily because of less seedsoil contact. Emergence was delayed by bulk densities greater than 1.20 and 0.90 gm/cm³ in Woodburn and Bashaw soils, respectively, because of increased soil strength. Data collected from three seeding dates made in the field in general confirmed the findings in the laboratory concerning the effects of soil moisture and temperature. Bezostaya emerged the slowest while Yamhill emerged the fastest. Seed protein content did not affect emergence. Applicability of the laboratory models to field conditions could not be established because of insufficient data.