The influence of soil water potential and soil temperature on the seedling emergence of wheat and barley

Abstract

The time for 50 % emergence of wheat and barley increases linearly with decreasing matric potential. This increase actually begins at matric pressures above pF 2.7. The rise in temperature makes emergence faster with in the range of minimum temperature (3.1°C for wheat and 1.9°C for barley) and the temperature where growth begins to slow down(about 31°C for wheat and 27°C for barley).The optimum range for 50 % emergence was obtained at a matric pressure range of pF 1.3—2.7 or —5.0— —0.20 m (water column) at a temperature of 10°C, which quite well corresponds to the situation in Finland during the emergence period in spring. A clear increase can be observed in the required heat sum for wheat and barley when the soil water potential reaches a critical point which was pF 2.8 or—6.3m for wheat and pF 2.7 or —5.0 m for barley. The total emergence as a function of matric potential for wheat and barley was determined over a period of 30 days at 10°C. In the wet side, pF 1,0 can be considered a limit, the total emergence decreasing with lower values. In the dry side, a corresponding decrease can be noticed in total emergence at pF above 3.0. The water uptake by seeds speeded up with increasing temperature from 10 to 25°C. Radicles of wheat and barley began to appear when the water uptake by the seed was approximately 50—60 % of the initial weight of the seed. The initial water uptake caused by the moistening of the pericarp due to capillarity was about 3 % for wheat and 5 % for barley at a soil water potential of pF 1.2.