DEGRADABLE MULCH AS AN ALTERNATIVE FOR WEED CONTROL IN LETTUCE PRODUCED ON ORGANIC SOILS
Lettuce in Quebec is primarily grown on organic soils, where weed control accounts for 30% of the pre-harvest production cost. As no efficient post emergence herbicide is available, weeding is done mechanically and manually. Using mulch could be a possible alternative to current practices. Degradable paper mulches (pale, pale/black, black/pale) were compared with polyethylene mulches (white/black or black) and a manually weeded unmulched control. The experiment designed as a randomized complete block with 4 blocks was carried out in 1999 and 2000. Polyethylene or paper mulches with at least one black side were effective in controlling weed growth in both seasons. During a warm season in 1999, air and soil temperatures of the paper-mulched plots were similar to those of the control. Day temperatures for the white/black polyethylene mulch were reduced by 2.8°C for air and 0.9°C for soil compared with the control. Soil humidity was highest under the polyethylene followed by the paper and finally the unmulched control. Lettuce grown on paper or polyethylene mulches had 25% greater marketable yield, with heads significantly heavier than those of unmulched lettuce. In 2000, the air temperatures for all mulches were similar to and 1°C above those of the control. When the black side of mulches was exposed to the sun, the soil temperature increased by 2.8°C compared with treatments where the pale side of the mulch was exposed. Lettuce grown in treatments with higher soil temperatures had longer stems. Soil moisture was similar in mulched and unmulched plots during the cool and rainy 2000 season. Growing lettuce on paper or polyethylene mulches increased marketable yield by 7% and resulted in significantly heavier heads compared with the control. Although similar yields were obtained with both paper and polyethylene mulches, the former has the environmental and practical advantage of being able to degrade in the soil at the end of the season.
Jenni, S., Brault, D. and Stewart, K.A. (2004). DEGRADABLE MULCH AS AN ALTERNATIVE FOR WEED CONTROL IN LETTUCE PRODUCED ON ORGANIC SOILS. Acta Hortic. 638, 111-118
biodegradable mulch, crisphead lettuce, Lactuca sativa L., organic soils, paper mulch, polyethylene, soil moisture