Coloured plastic mulches sustain canopy performance and fruit yield of the 'Micro-Tom' tomato in high-density plantings

Plastic mulches change the soil temperature and the light environment around plants, and may sustain crops where dense planting limits light. We evaluated red, blue and gray-on-black mulches against black mulch and bare soil at two planting densities (25 and 100 plants m⁻²) on dwarf tomato 'Micro-Tom' in a split-plot experiment. Plant height, root length, leaf area and dry weight were unaffected by the treatments, but the canopy's physiological condition was: at high density every mulch supported a higher maximum electron transport rate than bare soil, red mulch reaching the highest value recorded, and the SPAD index was highest over red and gray-on-black mulches and lowest on bare soil. Yield differences arose mainly from fruit size: red mulch produced the heaviest and widest fruits at both densities and the highest yield per plant at low density (117% above bare soil), whereas at high density all mulches out-yielded bare soil. High-density planting more than tripled the yield per area. Fruits from mulched plots carried fewer soluble solids, the concentration falling as fruit weight rose. Mulches thus sustained canopy performance and yield relative to bare soil, especially under dense planting, at a modest cost in soluble solids.