Evaluation of potting media for commercial nursery production of container-grown plants

Abstract

Release patterns of total nitrogen (N), ammonium-N, nitrate-N, urea-N, and organic-N from two rapid-release (urea and nitrolime), three synthetic (osmocote, sulphur-coated urea, IBDU or isobutylidenediurea), and one natural slow-release fertilisers (poultry manure) in five nursery media (peat, sand, peat-sand, peat-sand-sawdust, peat-sand-soil) were determined over a period of 14 weeks using leaching columns. The N from urea and nitrolime was recovered almost completely (83 to 100%) in the first two leachates. However, with slow-release fertilisers, rates of release of total-N and various N forms varied according to the media used. About 30–75% of the N was released over a period of 7–10 weeks- Urea-N, when present, was released first followed by ammonium-N and nitrate-N. The contribution from organic-N form was generally insignificant and inconsistent. The significance of the results is discussed in relationship to changes that occurred in potting media under commercial nursery conditions.