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Black polyethylene (PE) film is used for mulching in processing tomato ( Lycopersicon esculentum P. Mill.) in Spain achieving a generally high weed control but causing a serious waste problem. Few herbicides are available for tomato, so that a biodegradable mulching is the desired solution which should provide high yield, high weed control and be economically available. For 3 years, the same field trial was carried out in four areas of Spain using the following mulch materials in processing tomatoes: (1) untreated control, (2) manual weeding, (3) PE, black, 15 μm thick, (4) and (5) two types of biodegradable plastic mulch, black, 15 μm, (6) oxo-degradable plastic mulch, black, 15 μm, (7) paper mulch, black, 85 g m, (8) kraft paper mulch, brown, 140 g m and (9) barley straw, 1 kg m. Weed control, yield and economic aspects were analysed. Most frequent weed species were Convolvulus arvensis, Chenopodium album and Amaranthus spp. Here, we showed that despite differences in weed species, soil type and years, weed competition caused a similar yield decrease in all locations. A common regression coefficient could be estimated indicating that weed competition was responsible for a yield decrease of 3.3 to 4.4 t ha for each 10% of efficacy loss. Weed control was high for biodegradable plastics, paper mulches and PE ranging between 80% and 100% for all of them; also, yield was similar for all plastic and paper mulching treatments ranging between 72% and 108% of the yield achieved by PE. Here, we demonstrate that technically viable biodegradable alternatives exist for all four locations. From the economic point of view, PE gave highest benefits, mainly due to its low market price and to high yields despite removal costs, showing that its substitution will depend on prohibition. For locations with low-density weed infestations, manual weeding can be an alternative. [ABSTRACT FROM AUTHOR]

Abstract: Field studies of biodegradable polymerized vegetable oil-coated paper mulches were conducted to determine if these could replace non-degradable polyethylene mulches for stopping weeds and promoting growth of cottonwood trees. Tests were conducted over two growing seasons in two adjacent field sites in southeastern Missouri. At the end of the 2001 season, eastern cottonwood trees grown on the coated paper mulches had average heights (4.57–4.66m, 15.0–15.3ft), which were not significantly different from the control black polyethylene mulch (4.75m, 15.6ft). Tree heights were significantly less for uncoated paper mulch (4.45m, 14.6ft) or no mulch (3.90m, 12.8ft), presumably due to heavy weed growth around the trees. Uncoated paper mulch was extensively degraded after only about 4 weeks, while the coated paper persisted until the fall. Addition of ZnO to the oil coating delayed the onset of visible degradation, such as the formation of holes and tears, especially near the buried edge and above the drip tube. Similar results were seen for the 2002 study except that weed growth was not extensive so that tree heights for the mulched and bare plots were not significantly different. These results suggest that polymerized vegetable oil-coated paper mulches can function as effective mulches during the first year of tree growth, and thus, eliminate the need to use non-degradable polyethylene mulches. [Copyright &y& Elsevier]