 |
|
|
|
| |
The Garden Plot for November 09, 2007
3:55 PM - 4:00 PM
[Program Website]
Today's Highlight: “To Amend or Not to Amend - II”
Last week we began to look at the question of whether or not to add a soil amendment when planting a tree or shrub. As we went through the experimental evidence behind the theories, we found that the issue is complex and depends on soil type, climate, and tree or shrub species. This week I’ll report on a soil amendment study we initiated in Western Montana in 2007.
First, we talked to several local landscapers and nurserymen to find out what folks are using as soil amendments when planting trees. Then, this spring, we set up an experiment to test three different amendments:
1) a 16-16-16 soluble, quick-release fertilizer,
2) a compost made of decomposed wood bark and biosoilids with an N-P-K ratio of approximately 1.0-1.5-0.4 and a pH of about 5.9, and
3) a 2-1 mix of aged wood bark (0.2-0.2-0.2) plus alfalfa meal (2.7-0.5-2.2) with a pH of about 5.5.
We also added a control treatment in which no amendments were added.
We planted bare-root ‘Stella’ sweet cherry trees into holes amended with the three treatments after doing initial soil tests. The soil is a clay loam with low nitrogen and phosphorus levels, and high potassium levels. The trees were well-irrigated immediately after planting and received approximately 2-3” of irrigation water weekly through the summer.
Trees in all treatments survived and grew relatively well, despite a hot, dry July during which the average daily temperature was 96 F. Leaves began to color first in no amendment and compost treatments. Early leaf color can sometimes be an indication that the tree is stressed. However, early leaf coloring may also help the cherry trees harden off and survive winter better. We won’t know for sure until we take measurements again next year.
After leaf drop this fall we measured shoot growth to see if there was difference among the trees in different soil amendment treatments. We found that the trees that put on the greatest shoot growth were growing in soil with compost and no amendment. Newly planted bare root trees often show some dieback of the original branches before their roots establish and they begin to grow new shoots. Dieback increases when trees are stressed by hot, dry weather. The trees in our study with the most dieback were growing in the 16-16-16 treatment. However the new shoot growth of trees growing in the 16-16-16 treatment was almost as good as in the compost and no amendment treatments. The least dieback was found on trees growing in the treatments amended with Soil Pep plus alfalfa meal and compost.
In summary, our first year results don’t point to a clear winner, but suggest that when considering shoot growth and dieback right after transplanting, a lower pH, slow release plant nutrient compost addition may get some tree species off to a quicker start, without encouraging dieback.
Helen Atthowe's new short program of gardening tips
|
|
|
