The Q&A Archives: Trees In Alkaline Soil

Question: I have poplar trees, and my soil is very alkaline. I water once a day, and they are not making it. Do I need to do something different?

Answer: I'm assuming that you planted the trees recently. Correct watering is the biggest factor in maintaining healthy plants in our saline soils. Both our soils and water are high in salts. As added moisture evaporates from the soil, it precipitates and concentrates salts in the root zone of plants. This excess salt is carried via moisture throughout the plant, and accumulates in the leaf edges, where it kills the tissue and the leaf dries out and turns brown. It's important to water deeply and slowly. At least once a month, water deeply enough to "leach" or push salts well below the root zone. Here's some info on watering trees correctly:

Form a circular berm, or rim, to make a water well on the outside of the root ball. The goal is to keep water away from the trunk to discourage disease.

Add a three- to five-inch-deep layer of mulch around the tree's entire planting zone. Mulch conserves water by keeping soil temperatures cooler and reducing evaporation. Keep mulch about six inches away from the trunk to help prevent disease. Fertilizer isn't needed for a tree's first year.

Water the extended planting zone slowly and deeply. Soil should remain moist but not too wet during the first year of growth. Always water deeply (one foot the first year, gradually expanding to two feet as the tree matures) to encourage root growth and to flush salts below the roots' active growing area. Deep, infrequent irrigation is preferable. Frequent, shallow sprinklings do more harm than good. To determine how far water has penetrated, poke a soil probe (any long metal rod or screwdriver) into the soil. It will move easily through moist soil, stopping abruptly where soil is dry. As trees mature, expand the watering zone somewhat beyond the tree's canopy (or dripline), which is where roots are actively growing. I hope this info helps!

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