Far-red light affects photosynthate allocation and yield of tomato over red mulch

Plastic mulches are frequently used by both large- and small-scale tomato (Lycopersicon esculentum Miller) growers to conserve water, control weeds, and keep fruit clean. We hypothesized that changing mulch color to reflect more red light (R) and a higher far-red (FR) to R photon ratio (FR/R) would keep those benefits and improve tomato yield by altering phytochrome-mediated regulation of photosynthate allocation. Photodegradable and nondegradable forms of red plastic mulch were developed to our specifications. Number, size, and total fruit produced over the red plastic mulches were compared with those over standard black plastic. Photodegradable red mulch (placed over a leger of black plastic) increased fruit yield while it mas intact, but yield dropped to that of the black control after the red plastic degraded. Nondegradable red plastic resulted in greater yield. Early crop yield advantage of red mulch was evident whether it was placed directly over soil or over a layer of black plastic. We conclude that increased tomato yield over the new red plastic mulch was caused by reflection of FR to the growing plants and its subsequent phytochrome-mediated regulation of photosynthate allocation to developing fruit.