Potting Mixes AS 3743 (2003)

Long-term storage of potting mix, especially in warm, moist environments, can lead to depletion of the available nitrogen content of the mix. The concentration of nitrogen that is available to plants at potting will be decreased f rom what it was at manufacture. Marking requirements and the note in Clause 2.5.1 (c) relate to this problem. A 'best-before' date was discussed by the Committee, but was not considered to be the total answer, as retailers would not necessarily see any advantage in rotating mixes in the store, nor consumers any problem in using a mix after the date. Consumers do not generally understand this situation and would need to be educated to understand the fact that fertilizer may need to be added even to a premium mix that has been stored for some time. In view of this, and in order to increase the likelihood that plants will still have sufficient nutrients to produce plant growth for at least the short term after sale of the potting mix, it is suggested that potting mix ingredients should have an NDI (see Appendix E) of at least 0.6 at the time of their incorporation into a standard potting mix.