Organic Citrus Nursery

In the organic citrus nursery production, peat moss (a non-renewable natural resource) is the major component (45%) of the standardized IAMB organic growing medium. Its substitution with ECOS (commercial) or Pastazzo (citrus residues) composts in comparison with IAMB mix (control) was tested with Volkamer lemon, Troyer Citrange and Sour orange rootstocks. Using the first mixtures with both composts, all rootstocks showed lower growth than the control, due to the high pH values (>8) and the heavy media texture. Adding 20% of peat moss to the inert materials and 1.5% of Guanito in the second mixtures, the plant growth significantly increased to the control level, reducing pH value to 7.4. Rootstocks response to the tested media was different; the best performing was Volkamer lemon. Addition of elemental sulfur to Pastazzo-Guanito mixture reduced pH to 6.6 and improved Sour orange rootstock performance.