FERTILIZATION, ROOTSTOCKS, GROWTH AND YIELDS OF YOUNG 'ROHDE RED' VALENCIA ORANGE TREES

摘要

'Rohde Red' Valencia orange trees [Citrus sinensis (L.) Osb.] on three rootstocks, (C. volkameriana Ten. and Pasq., Carrizo citrange [C. sinensis (L.) Osb. x Poncirus trifoli-ata (L.) Raf.], or Swingle citrumelo [C. paradisi Macf. x P. trifo-liata (L.) Raf.], were used to determine if annual N rate and application frequency should be adjusted based on rootstock during the first 3-5 yr in the field. Treatments were arranged in a three (rootstock) x three (N rates) x three (N application frequency) factorial experiment with six individual tree replications per treatment. Annual N application rates ranged from 0.30 to 0.60 Ib/tree and N was applied in 8, 15, or 60 split applications per year. Rootstock had a significant effect on trunk circumference and yields in all three years with trees on C. volkameriana producing the largest trees. The greatest yields generally occurred for trees on C. volkameriana, followed by those on Carrizo and Swingle, respectively. The highest N rate increased yields over the two lower rates in year 3 for trees on C. volkameriana and Swingle rootstocks, but did not affect yields in year 4. In year 5, the 0.45 and 0.60 Ib annual rates increased yields over the 0.30 Ib rate for all rootstocks. There was no interaction between rootstock and N rate related to trunk circumference, but there was interaction between N rate and yields. Application frequency had no effect on trunk circumference, leaf N concentration or yields in any year.