To clarify the effect of reflective sheet mulching on photosynthesis of fruit tree canopies, we investigated, in sweet cherry and pear orchards, the photosynthetic photon flux density (PPFD) reflected from sheet-covered ground, the difference in net photosynthetic rate (
Pn) between sheeted and unsheeted (control) plots, and the effects of long-term mulching on leaf character and fruit quality. In complementary greenhouse experiments, we investigated the
Pn of leaves illuminated by various combinations of a range of artificial PPFDs at the abaxial and abaxial surfaces. Though the maximum reflected PPFDs from the control plots distributed below 10μmol m
-2s
-1in the cherry and 20μmol m
-2s
-1in the pear, those from the sheeted plots were around 200 μmol m
-2s
-1. Combining these results with those obtained in the greenhouse experiments led us to estimate that the mean increment of
Pnprovided by mulching would be about 2.1 μmol CO
2m
-2s
-1for cherry and about 3.2 μmol CO
2m
-2s
-1for pear. The observed increments of
Pnin the lower leaf layers of mulched trees were discussed. Long-term mulching resulted in leaves with sun leaf character and improved the coloring of cherry fruit, though there was no difference in fruit size between the mulched and unmulched plots for either cherry or pear.
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