Potential to double-crop plastic mulch

Abstract

Double-cropping of plastic (polyethylene) mulches has the potential to increase the cost-effectiveness while reducing the environmental impact of this technology for enhancing growth of vegetable crops. In regions with a short growing season, double-cropping of soil mulches hinges on being able to leave the plastic in the field over winter. This extended exposure to the elements may alter the physical and optical characteristics of the mulch, thereby influencing crop productivity in the second year of use. This study evaluated the physical characteristics and efficacy of black, clear and infrared transmitting (IRT) mulches over two cropping seasons in Saskatchewan. The crops planted were pepper (Capsicum annuum) and cucumber (Cucumis sativus) in the first year and tomato (Lycopersicon esculentum) in the second year. Early-season soil temperatures appeared highest under the clear mulch in the first year, but once the crop canopy was established there was little difference in soil temperature among plots having different mulches. Higher yields of both cucumber and pepper were produced in the first year by clear mulch than by black mulch or without mulch. All mulches were still physically sound at the end of the first growing season, but light transmission through the clear and IRT mulches was reduced relative to new mulch. Much of this change was due to soil and other debris on the surface of the mulches. There was little further change in the physical condition or light transmission characteristics of the mulches through the second year of use. Weed growth under clear mulch in its second year appeared to reduce soil temperatures, particularly relative to new clear mulch. Mulch type, either newly laid or year-old, had no impact on yields of marketable tomatoes. More fruit reached full red color prior to harvest in response to clear mulch than to no mulch (bare soil). Yields of marketable tomato fruit obtained on year-old mulch of all types were comparable to yields obtained with new mulch. These data suggest that double-cropping of plastic mulches can be done without loss of crop yield and provide significant savings in materials, labor and disposal costs. While clear mulch was generally the most beneficial for the production of warm season vegetable crops, it did not prevent weed growth in the second year which was problematic. Key words: Wavelength selective, light transmission, cucumber, pepper, tomato