Tomato plant growth during establishment as affected by root zone temperature under colored mulches

Soil warming is one of the benefits associated with the use of plastic film mulches. However, under high temperature and intense solar radiation, further warming of the soil may negatively affect plant growth during establishment. Greenhouse-grown tomato seedlings were transplanted to the field and exposed to a range of root-zone temperatures (RZTs), resulting from growing the plants in different seasons and by utilizing colored mulches that differed in their soil-warming ability. The objective was to determine the relationship of RZT to plant growth during the first 28 days after transplanting (DAT). Experiments were carried out in Fall 1999, Spring 2000, and Fall 2000. Black (n = 2), gray, red, silver (n = 3), and white (n = 2) mulches, and unmulched soil were used. RZT under mulch was measured with copper-constantan thermocouples placed 10 cm below the soil surface. Irrespective of the season, the highest mean RZT (from planting to 28 DAT) occurred under black mulch, and the lowest under white mulch. The mean RZT under black mulch was 4degreesC greater than under white mulch. In the spring season, vegetative top dry weight (DW) at 28 DAT was higher with increasing mean RZTs. In the fall seasons, vegetative top DW at 28 DAT decreased with increasing mean RZTs. Pooling data from fall and spring seasons, vegetative top DW at 28 DAT was found to fit a quadratic relationship with RZT. From this relationship, optimal RZT for vegetative top growth was calculated to be 25degreesC. Vegetative top growth during the first 28 DAT was correlated with subsequent vegetative top growth and fruit yield. In conclusion, RZT under colored mulches significantly affected tomato plant growth during the establishment period.