Trees in the existing orchards exhibited considerably less annual trunk growth increments than the new plantings, as would be expected of the shift from vegetative growth to fruiting. Trees were generally 5-6 years old, producing poorly, and not filling their space. Annual trunk growth increases ranged from10 - 38% in the year of compost application to 5 - 31% in the year after application. At the site with repeated compost applications, trunk growth increases were essentially unchanged. Compost has not statistically improved any variable measured, although some expected differences can be seen at the organically managed site, i.e. more kg. fruit per cross-sectional area of trunk with the higher compost rates.
Obviously additions of compost can not be seen as a quick fix for established trees which have undergone growth-inhibiting stresses. It is possible that longer term multiple applications of compost can improve tree performance, but economically a grower may be ahead to simply remove them, improve the soil (or condition causing the stress), and then replant.
Replant Composts can be applied before planting to either the tree row or individual tree holes. They can also be applied after planting. The 6 test sites included here utilized all three methods. Two of these tests included the use of new imported soil put into the planting hole (results under New Orchard planting below). Using compost as a replacement to fumigation is also being tested. Composts used include Stutzman chicken, Lincoln chicken, Sunland chicken, Lincoln cow feedlot, Cedar Grove yard waste, and Cascade yard waste, as well as leonardite, a humic acid material. Rates ranged from 0 - 45 tons/acre. Measurements taken included % trunk growth increment and leaf N.One site has been monitored for 3 years now. It is showing that additions of 20 to 40% compost (by volume) to the planting hole can improve growth. Interestingly, there was no measurable effect the first year. A second site with in-the-hole treatments is only in its first year, again showing no differences. The sites with broadcast compost applications are showing no significant differences.
Overall trunk growth increases ranged from 23 - 75% for first leaf, 40 - 152% for second leaf, and 35 - 71% for third leaf (one test). Comparing the method of application, compost added to the planting hole appears to give a better tree response than broadcast applications. However, use of high salt composts in the planting hole can inhibit tree growth or kill the trees and should be avoided or greatly diluted.
New orchard planting Two orchard sites were replanted using new soil in the planting hole. Three sites were newly planted on previously unfarmed soil. Compost was either added to and mixed in with the soil material placed into the augured tree hole or broadcast onto the tree row. Broadcast applications include before planting with incorporation and after planting. Materials added include leonardite, Stutzman chicken, Cedar Grove yard waste, Sunland chicken, BION, BION plus ground fish, an organic mineral mix, off-site new soil, on-site old orchard soil, and a biosolid soil mix. Rates ranged from 0 - 40% volume of the augured hole, 0 - 20 tons per acre, and 0 - 2 cups of leonardite/tree. The Biosolid mix treatment was 100% volume of the augured hole. Measurements taken included % trunk growth increment , leader growth, and leaf N.Adding compost along with new soil improved growth at one of the two replant sites only the first year. The second site showed a trend of greater growth in year two, but it was not significant.
Compost treatments dramatically improved growth at a new site where the compost was added to the hole. Here leonardite enhanced growth 2 years in a row. The broadcast compost treatments with incorporation have not improved tree growth to date.
Almost all trees planted in new ground or with new soil have grown very well. Trunk growth increases have ranged from 57 - 142% (first leaf), 61 - 153% (second leaf), and 20 - 59% (third leaf, one test). The data from these tests illustrate how current management, including soil fumigation, does not appear to be returning replant sites to their full production potential.
Interplant At one site, new trees were interplanted into a young planting where some trees had failed. Various composts and rates were added to the planting holes. Very few trees grew well. Trunk growth increases ranged from 21 - 34%.For more information, contact David Granatstein or Patty Dauer, Washington State University Tree Fruit Research and Extension Center, Wenatchee, WA. Tel. (509) 663-8181 x.222. email:granats@wsu.edu
This research was conducted as part of a cooperative effort between WSU and The Food Alliance. Funding for this project comes from a grant from the W.K. Kellogg Foundation Integrated Farming Systems program. Summary of 1997 DataTrials on orchard plantings - New Plantings and Replant with new soil