Quote:
|
When they say it helps plants build up defences what they are saying is that a tree that has sufficient nutrition is less likely to be as severly affected by harmfull insects or disease. Healthy trees are stronger right
|
Ok, there's a few problems with viewing the consequences to the tree of the addition of available Nitrogen to the soil, in this way.
1. Fertilizers do
not feed the tree, they are
not nutrients. They are a combination of elements some essential some not. Nutrition for the tree is what is created on in the leaves through photosynthesis.
2.All natural soils are very low in the forms of Nitrogen required by perennial plants, trees together with all plants are genetically predetermined to take up whatever available Nitrogen there is in the soil around their roots and the mycelia of the sybiotic fungi they (nearly all) rely on.
3.The take up of Nitrogen leads to the commitment of stored Carbon resources stored by the tree, primarily in the formation of Chlorophyll molecules and at the rate of 33:1 (Carbon:Nitrogen) Nitrogen leads directly to the production of flushes of very green (chlorophyll rich) new growth
4. The tree does not have a limitless supply of stored Carbon resource, and as a biological system prioritizes the allocation of that resource...sadly defence is last on the list of the priorities....new growth is first! (Sure over time through its growth cycles the tree will capture and store more Carbon, but the debt it builds up has to be repaid and the loss in availiable Carbon impacts most heavily on the lowest priority areas that being defence.
5. Rather than being a boon for defence fertilizer induced new growth is the opposite, it actually has less defence than the older leaves.
6. Healthy trees are stronger more resiliant trees, however foliage density and colour alone are not absolute indicators of tree health.
7. The solution is in the soil and root environment but adding Nitrogen rich compounds in the form of fertilizers is not the way to create sustainable long term benefits to trees.