The period between removing an orchard and replanting is a good time to correct the soil pH and nutrient levels in the soil.
Tim Smith, Extension educator for Washington State University in north central Washington, recommends checking the soil at least a year ahead of planting so you can make some corrections. Nutrients can be stirred in and disked in after the soil has been ripped.
This is your opportunity to work the lime and nutrients into your soil, Smith said. Its going to be a long time before you can stir the ground again.
The soil profile should be checked carefully not just the top foot. Soil with a pH level of 6.0 on the surface might have levels as low as 4.0 or 3.5 deeper in the ground. Apply lime if necessary to raise the pH level. Ideally, an orchard soil should be neutral, at around 7.0.
Also look at major nutrients. Washington tends to have rich soils that are rarely short of potassium. But if the potassium level is low, which can happen, its good to correct that between orchards when there is no concern about causing bitter pit in the fruit, Smith said.
Phosphorus is beneficial for young trees, but if soil tests indicate that the phosphorus level is in an acceptable range, theres no need to apply more. If its low, now is the time to stir it into the soil so that it will be available to the young trees in their first two or three years before it becomes bound up in the soil.
Zinc and boron
If the orchard site has been out of production for two or three years, the zinc that was in the soil can become tightly bound and unavailable to the tree. Zinc and boron deficiencies can become problems in vigorously growing trees but might be difficult to diagnose. Young trees can outgrow the supply of boron in the soil even if boron has been applied.
Symptoms include short internodes on the vigorously growing shoot tips and leaves that are closer together than normal. Sometimes, new leaves will be yellow and cupped. The following spring, there will be dieback of the shoot tips.
Fumigation is critical for controlling replant disease when any tree fruit is replanted, Smith said. Growth of trees on unfumigated replant sites will be impaired for the life of the orchard.
Fumigation can also help control a large insect called the ten-lined June beetle, whose larva feeds on tree roots and can be very damaging to young trees. The insect is often found in dry, sandy sites and cannot be controlled after the trees are planted. It can be a problem in new ground as well as replanted orchard ground and is the only reason for fumigating new land. Check the site the season before you plant, Smith recommended.