EFFECT OF POLYETHYLENE AND PAPER MULCHING ON YIELD AND EARLINESS OF PICKLING CUCUMBER
The soil temperature may be raised by different kinds of mulching. Polyethylene, paper, bitumen, straw and peat among other things are used as mulching-materials. Of these materials polyethylene, paper and bitumen are able to raise the temperature in soil. The greatest success in practice up till now is gained by the polyethylene mulches. They have brought about a 40–50 per cent increase in yield of pickling cucumbers during growing-seasons with a normal temperature. However, when the temperatures were lower than normal, the increase in yield rose up to 100–200 per cent.
Because the polyethylene mulch is non-decaying, it has to be removed from the field after the growing-season. This is troublesome and it demands extra work. The paper mulch on the other hand becomes mouldered in soil. Using them saves the removing-work.
Two years ago the paper factories in Finland became interested in the use of paper for mulching-purposes. The first paper mulches made in Finland were tested at the Department of Horticulture in 1967. It was found that most of them were not strong enough for mechanical handling. Furthermore, the results of the first tests showed that the transmission of the visible and thermal radiation of solar spectrum through the paper mulch was poor. As a result, the temperature under the paper mulches during the day time was lower than under the plastic ones.
As an outcome of these experiences obtained from the preliminary tests in 1967, the material for paper mulch was improved by adding fiber and polyethylene to it in order to increase the pulling-strength. The transmission of the visible and thermal radiation of paper mulch was increased by impregnating the paper with oil.
The improved paper mulches and the transparent polyethylene mulch were compared in an experiment carried out at the Department of Horticulture in 1968. The mulches were:
- Clear polyethylene, 0. 03 mm thick, non-perforated.
- Clupak-paper 80 g/m2, impregnated with paraffin oil, coated with clear polyethylene 15 g/m2, perforated
- Clupak-paper 90 g/m2, coated with black polyethylene 20 g/m2, perforated
- Crepe kraft-paper 90 g/m2 with synthetic fiber, non-perforated
The mulches were rolled out with a special machine for spreading-work