Boron and High GF P.radiata
Is Boron demand increasing in our higher genetic P radiata trees?
I have many foresters, and farmers, phoning about what to look for, when assessing a stand of boron deficiency, in a stand of P Radiata . My appraisal of the situation outlines such things as, short fat dumpy trees, with no apical dominance, sinuosity within the stems, or branches, and in extreme cases, apical die back.
Most of these symptoms become apparent in the autumn. I had a farmer ring up from Masterton, he asked me the same question.'' What do I look for to see if my stands are boron deficient. After I told him what to look for, he said, "well I'm a bit bemused, I'm standing adjacent to two wood lots. The first one is about 28 years old, and to my mind it looks excellent. They are due for felling ,there is no dead tops no sinuosity in the stems, or branches, and generally they look very healthy. However, a stones throw away I have a five year old stand of P Radiata, which have got all the symptoms you have outlined . He said, he had no doubt that his five year old stand was boron deficient, and he was about to rectify that by applying Boron chip. But why he asked, are the older trees looking all right..
To answer this question, I gave him a history lesson. I said, when we first started to notice boron deficiency, symptoms started in trees about 4 or 5 years old. Symptoms generally were resin bleeding on the terminal buds, and in the critically deficient areas, terminal die back.
This was around the mid to late 70s, and as our knowledge of the deficiency grew, there appeared to be more symptoms popping up as the years went by. It wasn't until the early 1990s, that we were discovering two year old trees that were becoming extremely boron deficient. In fact, a lot of the plantations that were planted during this time desperately need an application of Boron, at a younger age than initially recommended .
Why were we seeing more of this deficiency earlier on in a trees life, than we had previously noticed. The answer became apparent, after a series of trials were laid down in the early 1990s, looking at the nutrient requirements of our higher G.F. rated trees.
In the old days, P Radiata seed was collected by climbing good form, and dominant trees, and collecting the cones. The resulting seed was the basis of our plantation forests then. Now all our trees that are available on the market, are genetically superior in every way, both in growth and form . These genetically superior trees require more boron, at an earlier age than the "old climb and select crops".
This is not to say, in any way that these higher, genetic trees are inferior, quite the opposite. These selected families have proven to be the best for our growing needs. Just like with animals, selected breeding with trees is no different. As we reduce our genetic base, we are finding that certain families have certain characteristic, all of which require boron at an earlier age. So much so, that we even fertilise trees with boron that have yet to leave the nursery, so as to help them in their new environment once they get planted out. In many cases, these trees will require an application of boron, prior to the start of their second growing season.
In order to get a handle on the optimum time to apply boron, a series of trials were carried out with boron rich seedlings, and boron deficient seedlings. An interesting spin off eventuated from these trials, in that, it was found that the most significant advantage of seeds that were boron rich, was that they could withstand an extra five degrees of frost before mortality was recorded.
This was a very interesting phenomenon, and the reason why this has occurred is still speculative. One suggestion is that, boron rich seedlings have a much stronger terminal bud and can withstand a higher degree of frost. This may well be the case, however if you are considering planting P Radiata in frosty areas, I would suggest that you consider planting P Radiata cuttings, as opposed to P Radiata seedlings. Your survival rates will drastically improve, especially if you are planting aged cuttings.