INFLUENCE OF ORIENTATION ON WHEAT YIELD AND PHOTOSYNTHETIC PHOTON FLUX-DENSITY (Q(P)) AT THE TREE AND CROP INTERFACE IN A PAULOWNIA-WHEAT INTERCROPPING SYSTEM

An on-farm field research study to characterize wheat yield in plots o riented 2.5 m east (E), west (W), and north (N) from the canopy of a n orth-south row of 11-year-old Paulownia trees was conducted at Zhengzh ou, Henan Province, PR China. Wheat yield was higher on the east orien tation compared with the west and north as determined by total grain w eight and 1000-grain weight. Measured photosynthetic photon flux densi ty (Q(p)) was higher on E orientation during critical stages of wheat development. Soil pH, soil organic matter, available nitrogen, phospho rus, and air temperature parameters did not affect yield differences. In a second, related study, yield data from plots with and without pla stic root barriers, placed to a depth of 1 m between the tree and wint er wheat yield plots located 2.5 m E or W of the tree row, indicated t hat tree and crop root interaction had no effect on total grain weight or 1000-grain weight. However, there was a significant increase in yi eld of the E orientation as compared with the W.