TEMPERATURE AND WATER REQUIREMENTS FOR GERMINATION AND EMERGENCE OF LUPIN

The responses of germination, emergence, and pre-emergent growth of narrow-leafed lupin (Lupinus angustifolius L.) to a range of soil temperatures and matric potentials were determined in 2 replicate experiments with different seedlots and sowing techniques. Although absolute responses to temperature and water availability differed between experiments, the patterns of the responses did not. Optimum temperatures were close to 20 degrees C and base temperatures were 0-3 degrees C. At temperatures >23 degrees C, germination and growth were highly variable and hindered estimation of ceiling (maximum) temperatures; the lowest was about 30 degrees C for germination. Under optimum conditions, germination took 1-1.5 days and emergence from a depth of 4 cm took 4-4.5 days, equating to 75 degrees C.day (base temperature 2 degrees C). The minimum soil matric potential for growth was -1 to -2 MPa, and emergence was more sensitive to low matric potential than was germination. Hypocotyl extension was more sensitive than radicle extension to low matric potential, leading to relatively long roots at the time of emergence.