Effect of N Source on Photosynthesis and Plant Dry Matter Yield of Tomato

The objective of this study was to determine if winter legume or grain cover could support net photosynthesis (P n ) and plant dry matter production comparable to recommended rate of synthetic N. The following winter/spring fertility treatments were applied: 1) 0 N winter/0 N spring, 2) 0 N winter/90 kg·ha –1 N spring, 3) 0 N winter/180 kg·ha –1 N spring, 4) 0 N winter+abruzi rye/0 N spring, 5) 0 N winter+hairy vetch/0 N spring, and 6) 0 N winter+crimson clover/0 N spring. `Mountain Pride' tomato was planted in all plots in spring. Plant dry weight and P n were measured at flowering, fruiting and prior to senescence. The highest P n (22.78 μmol CO 2 /m 2 per s) and leaf dry weight (115.2 g/plant) were obtained at fruiting, while highest branch dry weight (194.5 g/plant) occurred prior to senescence. There was significant increase in plant dry weight during reproductive growth phase. Tomato plants receiving supplemental N from crimson clover or hairy vetch had P n and plant dry weight comparable to those receiving synthetic N. The results of this study indicated that legume cover crops were as effective as commercial N fertilizer for supporting photosynthesis and vegetative growth of tomato.