Biodegradable mulch instead of polyethylene for weed control of processing tomato production

Abstract

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⁻², (8) kraft paper mulch, brown, 140 g m⁻² and (9) barley straw, 1 kg m^−2.. 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⁻¹ 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.