RE: Soil mix!!

From: millern at wave.co.nz on 2002.04.03 at 16:36:55(8431) Susan Here in New Zealand we use pine bark a lot in potting mixes (because we have large quantities of it, and peat supplies are limited). We mostly use bark from the Monterey Pine, Pinus radiata. However, it needs processing before it can be used. The following exerpt from an article in 'Begonia News', a local publication, by Dr Rod Bieleski, a horticultural scientist, will probably tell you more than you ever wanted to know :) "We take for granted the barkbased potting mix we use today, but a lot of research had to go in before it could be reliably used. The man who did most of the work was Munoo Prasad of the old MAF (Ministry of Agriculture and Fisheries) Levin Horticultural Research Centre, and in the 1980s he spent several years in identifying and solving problems. Three particular kinds came from using pine bark. It's very low in nutrients, has a tot of tannins, and creates too much acid even for acidlovers like Camellias. It has to be pre-fed with nitrogen  if not, the bark gobbles up all the nitrogen from the fertiliser you put on before the plant gets a chance. And it has to be mixed with a surprisingly large amount of dolomite lime to keep the acidity in check, and to precipitate the tannins. Quite a lot goes into making a good mix before it reaches you. There's a tot more to it than just mixing up ground bark and pumice sand. "During the 7 months or so we are growing plants, the mix is progressively changing. The bark keeps breaking down and releasing small particles, impeding drainage and generating more acid. The bark also keeps gobbling up nitrogen. Though we apply nutrients in our fertiliser, we aren't providing any buffer for the acid. And then we store the bark for 5 months until the next season. We've stopped feeding the nutrients, but the mix keeps on breaking down, keeps on making acid and keeps on sopping up any residual nutrients." I hope this helps Nick Miller +More On 2 Apr 02, at 16:54, Cooper, Susan L. wrote: > Can someone explain the pine bark to me? I've never quite gotten it > clear in my mind... I thought folks put down pine mulch because > "something" in the pine bark helps prevent weeds from growing. The > explanation given to me was that not much grows in a pine forest > (except the pines, duh) due to some inhibitor with the pine needles, > or roots or ???. Am I just totally nuts or has anyone else ever heard > this? > > If it isn't true I'll start adding a little pine bark to my mix, it is > easy to find here (up north), people use it for decoration. > > Susan Nick Miller Rotorua, New Zealand

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