Photosynthesis measurements were recorded on 48, 57 and 72
DAT on fully expanded leaves. Fruit setting on plants occurred
around 58 DAT while 73 DAT was just before the beginning
of ripe fruit harvest. Consistent with the data on fruit yield and
total biomass, tomato leaf photosynthesis was higher in plants
grown on vetch than bare soil at almost all N rates at the three
measurement dates (Fig. 2). Photosynthesis trended slightly
upward with increasing N rate in vetch soil (Fig. 2a) but in
bare soil grown plants it increased to a peak at 50–100 kgNha–1,
declining at the 200 kgNha–1 rate (Fig. 2b). Compared with
photosynthetic rates before and at fruit setting, leaf
photosynthesis declined at all N rates in bare soil when the
fruit were at an advanced stage of ripeness; however, the
decline was more pronounced in plants grown in bare than
vetch soil.