THE INFLUENCE OF MULCHING ON T° AND HEAT FLUX IN THE SOIL AND T° JUST ABOVE THE GROUND IN CONNECTION WITH NIGHT FROST PROTECTION
Researches are made on the influence of soil mulching on the factors : soil temperature, air temperature near the soil surface, heat flow rate in the soil.
In spring the application of black polyethylene film generally gives a small increase of the chance of night frost, an increase of the temperature fluctuations of the air near the soil surface and a decrease of the temperature fluctuations in the soil. In common with the other applied kinds of soil mulching the humidity of the soil is increased.
In general the use of transparent polyethylene film gives a decrease in the chance of night frost and an increase of the temperature fluctuations in the soil, however with an increased mean temperature of the soil.
The application of water-mattresses reduced the chance of night frost more than the use of transparent polyethylene film. The temperature fluctuations in the soil are also less at an increased mean soil temperature.
All that is explicable from the fact that black polyethylene film absorbs a great part of the radiation and delivers much heat to the air by day. More heat is also lost by radiation. At night the film opposes the radiation of the soil. Transparent polyethylene film transmits a considerable greater part of the radiation, through which the soil is heated strongly during the day. In consequence of this the heat flow rate in the soil is increased and at night more heat can be delivered.
With the application of water-mattresses much heat is collected in the water by day and at night more heat is delivered than with uncovered soil.
By using these kinds of soil mulching the evaporation is prevented, by which the humidity of the soil with increase more than of uncovered soil. This will also increase the heat flow rate in the soil.