Effects of reflective sheet mulching on net photosynthesis, leaf character and fruit quality of cherry and pear

Abstract

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 adaxial and abaxial surfaces. Though the maximum reflected PPFDs from the control plots distributed below 10 μmol m2 s-1 in the cherry and 20 μmolm2 s-1 in the pear, those from the sheeted plots were around 200 μm-2 s-1. Combining these results with those obtained in the greenhouse experiments led us to estimate that the mean increment of Pn provided by mulching would be about 2.1 μmol CO2 m-2 s-1 for cherry and about 3.2 μmol CO2 m-2 s-1 for pear. The observed increments of Pn in 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.