Effects of Calcium and Magnesium on Plant Growth, Biomass Partitioning, and Fruit Yield of Winter Greenhouse Tomato

Abstract

Tomato (Lycopersicon esculentum Mill) `Trust' was grown on rockwool with nutrient solutions containing two levels of calcium (150 and 300 mg·L-1) in factorial combination with three levels of magnesium (20, 50, and 80 mg·L-1) in Winters 1997 and 1998, to investigate the effects of calcium and magnesium on growth, biomass partitioning, and fruit production. Plants grown at 20 mg·L-1 Mg started to show Mg deficiency symptoms (leaf chlorosis) at 8 weeks after planting. The chlorophyll content of middle and bottom leaves increased with increasing Mg concentration in the nutrient solution. At 300 mg·L-1 Ca, total fruit yield and fruit dry matter increased linearly with increasing Mg concentration; marketable fruit yield and total plant biomass showed similar response but to a lower degree. At 150 mg·L-1 Ca, total plant biomass, fruit dry matter and yield peaked at 50 mg·L-1 Mg. The biomass allocation to fruit increased while allocation to leaves decreased with increasing Mg concentration. The Mg effects on total and marketable fruit yield were mainly due to its influence on fruit yield in the late growth stage. Incidence of blossom-end rot (BER) at 150 mg·L-1 Ca increased linearly with increasing Mg concentration while it was not affected by Mg concentration at 300 mg·L-1 Ca. For a winter greenhouse tomato crop, the appropriate Ca and Mg concentrations for tomato production appear to be at 300 and 80 mg·L-1, respectively.