GROUND COVERS AFFECT RASPBERRY YIELD, PHOTOSYNTHESIS, AND NITROGEN NUTRITION OF PRIMOCANES

Raspberries (Rubus idaeus L.) were grown for 5 years with three floor management treatments: clean cultivation (CC) and ground covers of whi te clover (Trifolium repens L.) (WC) and perennial ryegrass (Lolium pe renne L.) (PR). Primocane growth was strongest with WC and weakest wit h PR. Fruit production did not differ between WC and CC treatments and was higher than with PR. On 22 Aug. and 10 Sept. in the last year, pr imocanes grown with WC were taller, had more nodes and a higher dry we ight, contained more N, and had retained more leaves than those grown with PR. Net CO2 assimilation per unit leaf area was higher with WC th an with PR, and the difference was greater at the more proximal positi on, The estimated net CO2 assimilation rate per primocane was more tha n twice as high with WC than wi.h PR,