Alternative Mulches for Sustainable Greenhouse Tomato Production

Soil mulching has advantages for horticultural crops, from both agronomic and phytosanitary points of view. The most common material used is polyethylene (PE); however, promising alternatives from the circular economy exist, such as straw (ST) and biodegradable biopolymers (BBs). The effect of the three aforementioned mulches was evaluated and compared to non-mulched soil in a Mediterranean greenhouse for two years of an organic tomato crop. Physical (moisture and temperature) and physicochemical properties of the soil, in addition to crop yield and the effect of the mulches on weed control, were assessed. Additionally, the deterioration of plastic mulches was assessed. The temperature was higher in the mulched soils, but few differences were found between soil and BB at the end of the second cycle. Evaporation was lower in mulched soil, in general, without big differences among the types of mulch. Crop yield did not show differences. At the end of the trials, of the 16 physicochemical variables evaluated, only a slight increase in pH was detected in the ST-mulched plots. BB film degradation reached 5.6% and 6.7% of the total surface at the end of the first and second cycles, respectively. Weeds were equally limited for PE, BB, and ST mulches, but cereal seeds contained within the straw germinated randomly all over the crop cycle. In summary, straw and biodegradable plastic mulches offered the same benefits as conventional PE mulch. Therefore, they can be considered a feasible and more sustainable option, in addition to being consistent with the principles of the bioeconomy.