INFLUENCE OF STORAGE OF SUBSTRATE ON GROW TH OF CHRYSANTHEMUM AND P CONTENT OF SUBSTRATE USING DIFFERENT EXTRACTION METHODS

Influence of storage duration on P availability in peat and peat-clay mixtures of different pH has been examined. 1. With peat no influence of storage on growth and P content of substrate has been found, regard less of pH. However with peat-clay mixtures of high pH (7) strong infl uence of storage has been observed, leading to large growth depression s with storage longer than 6 weeks. 2. Yield decline may be explained partly by decreasing phosphorus availability All methods extracted let s P increasing storage time. ''Weak'' extraction solutions (Water, CAT ) extracted particularly low P contents and were therefore suitable to indicate P deficiency. 3. An additional and surprising result was tha t with peat-clay mixtures of high pH freshly applied P resulted only i n a very small growth response. Reasons for this could be the very low N contents in stored substrate.