Timo Silver , Markku Saarinen

Terveyslannoituskohteen määrittely turvemailla

Silver T., Saarinen M. Terveyslannoituskohteen määrittely turvemailla.

Tiivistelmä

In Finland there are approximately one million hectares of nitrogen-rich drained mires which may suffer from deficiency of potassium (and phosphorus). These site types are originally wet sedge fens with thick peat layers. The degree of deficiency of mineral nutrients varies, but it is propable that fertilizing with potassium and phosphorus would improve growth in most cases. This kind of fertilization which aims at rebalancing available nutrient stores for trees is called “repairing fertilization”. However, it is almost impossible to say when there is a question of repairing fertilization or normal fertilization meant to improve growth. This study introduced the assessment of repairing fertilization plan simultaneously with different methods to determine the need of such a fertilization. Earlier instructions emphasize visible potassium and phosphorus deficiency symptoms or needle analyses. However, these methods alone do not provide enough information to reliably determine the need of fertilization. For example the limit of severe potassium deficiency in Norway spruce needle analysis is 5.2 mg g-1 while visible deficiency symptoms will not be apparent until the value drops down to 4.0 mg g-1. In other words spruce may suffer from severe potassium deficiency long before it can be seen by human eyes. The problem of needle analysis is commonly it‘s reliability as needles are collected only from 5–10 trees per site. The results indicate that determining the need of repairing fertilization should be based on both the mire site type (sedge fens) and the thickness of the peat layer (over 0.4–0.5 meter). Determining the need of repairing fertilization on drained mires should not be solely based on the needle analysis and visible potassium deficiency symptoms as the case has been so far.

Vastaanotettu 31.10.2017 Julkaistu 1.1.2001

Katselukerrat 1397

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