Vitreous controlled release fertiliser compsn. - comprising a vitreous matrix formed from phosphorus pent:oxide and glass modifying oxide cpds.

摘要

A particulate fertiliser compsn. comprises a vitreous matrix formed from P2O5 as a glass forming oxide together with a plurality of glass modifying oxides selected from alkaline earth) metal oxides and includes =1 oxide of K, ea, and/or Mg. It also incorporates N2 as Ca cyanamide, the nitreous matrix being water soluble such that, when the compsn. is immersed in water, the constituents are released into soln. The compsn. is useful as a slow release fertiliser compsn. and may contain other active ingredients one desirable application of the compsn. involves young plants, seedling or saplings, in that the fertiliser possesses an induction period preceding the release period when no or little fertiliser is released. The rate of release of phosphate glass is lowered by incorporating calcium as other oxides. N2 is incorporated into the fertiliser by mixing all the other ingredients, and fusing to form a base glass to which N2-releasing agent is added. The nitreous phase may also contain trace elements e.g. Fe.B.Mn.Cu, Zn. etc.