Mulching for tobacco cultivation in Japan
Mulching covering the ridge by plastic film is widely used for tobacco cultivation in Japan. It was introduced in the 1960s and was used in 98% of the total tobacco cultivation area in the 2014 crop. There are two main advantages of mulching by plastic film, and that closely relates to Japanese climate. One is to prevent the erosion of soil and fertiliser in the rainy season. Another is to accelerate initial growth by maintaining soil moisture and temperature that allows early harvest before the typhoon season. Today, many kinds of mulch are utilised in Japan.
Polyethylene film is the most popular and there are four types of transparent, black, silver and bicolour. Each of them has different properties in maintenance of soil temperature and in control of weeds and/or aphids.
Biodegradable plastic film has been used since the 2000s. It is eco-friendly material because it is decomposed to carbon dioxide and water by soil microorganisms. Therefore, it is not necessary to remove and discard after end of harvest. The penetration rate of biodegradable plastic film in the 2014 crop was only 9% because of its price and quality in the rate of decomposition.
Living mulch between tobacco rows using wheat or barley plants has recently been introduced. The penetration rate of living mulch in the 2014 crop reached 16%. In addition to the prevention of soil erosion and control of weed, it is effective to control the soil-borne disease, black shank, by preventing an adhesion of soil to tobacco leaves at the time of rainfall.