Плохая дренаж почвы: главная причина гибели 80% деревьев и кустарников

How important is determining how well the soil drains in a site before planting a tree or shrub? According to Dr. William Fountain, University of Kentucky Extension Professor Emeritus of Arboriculture and Landscape, eighty to ninety% of disease and insect problems with woody plants can be attributed to stressed plants due to soil conditions. Plants commonly fail to establish and thrive because of too little or too much water. The proper amount of water is more critical for growth than fertilizer. Often, plants die from too much water due to poor soil drainage. Soil contains little oxygen when it becomes saturated with water. Without oxygen, the leaves wilt since the plant’s roots cannot absorb the water even though it is abundant. The appearance of drought symptoms increases the temptation to add more water, which compounds the problem. Soil with minimal oxygen allows plant pathogens to grow, killing roots and making it even more difficult for plants to absorb water. How is soil drainage determined? Soil color can indicate poorly drained or compacted soils. Well-drained soil are brown or reddish. Blue-gray soils have very little oxygen. The soil’s naturally occurring iron has not had sufficient oxygen for it to turn a red color. Blue-gray and white soils are almost always very poorly drained. Plants preferring well-drained soils should never be installed in these soils. Species adapted to wet and flooded sites are more likely to survive. To discover how well the soil drains, even on the side of a hill or slope, conduct a perk test. This simple test takes relatively little time and is a small investment for plants that beautify landscapes for many decades. To conduct the test, dig a hole in the soil with a shovel or posthole digger. The diameter can be relatively small, three inches or larger, and should go down at least 12 inches; 18 inches is better. The best depth is determined by measuring the soil ball height of the plant wanted for that location. The planting hole can be used for the test. Avoid digging when the soil is wet, as the sides of the hole can be glazed. If the soil is glazed, water will not drain and will give false results. Next, fill the hole with water and allow it to drain. Then, refill the hole with water and measure the amount of time it takes to drain. Ideally, the water should drain at the rate of about 2 inches per hour. Anything between 1 and 3 inches per hour is acceptable. Anything significantly less than 1 inch per hour indicates the site is poorly drained, and you will need to improve the drainage or select plants that grow on waterlogged sites. It is not unusual for planting holes in the same landscape to drain at significantly different rates. To deal with a poorly drained site, do not add sand to heavy soils. Contrary to what logic would indicate, adding sand to heavy soils slows the drainage. Furthermore, do not add large amounts of organic matter to poorly drained soils. When organic matter breaks down in poorly drained conditions, toxic gases and other byproducts of decomposition are created that are toxic to roots. Finally, amending the backfill in planting holes often makes it more difficult for water to drain. It is best to put the soil taken out of the hole back into the planting hole without adding anything to the soil. Poorly drained sites can be located on a slope. If the site is on the side of a hill, dig a trench from the bottom of the planting hole toward a lower site. Lay a small plastic pipe in the bottom of the hole that will drain excess water downhill until it comes to the surface. One inch drop for every 5 feet of run is usually sufficient for water to drain. Cover the end of the pipe with a piece of window screen and a handful of rock to improve movement of water from the soil into the pipe. Redirecting water from uphill areas and the downspouts on a house reduces the amount of water in the plant’s root zone. Selecting trees for poorly drained sites is the best way to increase the likelihood of the plant surviving. These include bald cypress (Taxodium distichum), black gum (Nyssa sylvatica), sweetgum (Liquidambar styraciflua), sweetbay magnolia (Magnolia virginiana), swamp white oak (Quercus bicolor), and American holly (Ilex opaca). Shrubs for these sites include: summersweet (Clethera alnifolia), common witch hazel (Hammamelis virginiana), winter berry holly (Ilex verticillata), spicebush (Lindera benzoin), Virginia sweetspire (Itea virginica), and viburnum species (Viburnum spp.). A list of more trees and shrubs is available at the Daviess County Cooperative Extension Service in the publication “Soil Percolation: A Key to Survival of Landscape Plants” ( https://publications.mgcafe.uky.edu/sites/publications.ca.uky.edu/files/ID237.pdf ). For more information about a perk test, contact the Daviess County Cooperative Extension Service at 270-685-8480 or [email protected]. Annette’s Tip An option to handle water runoff is to install a rain garden. Rain gardens are sunken areas designed to collect water, allowing more time for it to soak into the soil. Plants in rain gardens must be able to tolerate wet and dry conditions. Upcoming Event “Winter’s Chill for Summer’s Thrill — Winter Sowing Native Seeds” is scheduled for Sept. 17 at the Western Kentucky Botanical Garden, 2731 West 2nd St. in Owensboro. Guest speaker Extension Master Gardener Regenia Sims will talk about growing native plants from seed for your landscape. Free native plant seed sample will be available for attendees.