Source:Roger WilliamsFor Release: May 8, 2016
Extension Ed., Ag/4-H
Cherokee County
456-6163
Mulching Basics
A Mulch is any material that provides protection and improves the soil when applied to the surface. Depending on the type of mulch, it can help to: 1) Protect shallow rooted plants from freeze damage, 2) Improve soil structure and nutrient availability, 3) Reduce weed growth, 4) Reduce soil temperature extremes, 5) Retain soil moisture, 6) Prevent vegetables from making soil contact, 7) Prevent soil erosion from heavy rain damage.
There are two types of mulches; organic and inorganic. Organic mulches include wood chips, sawdust, straw, grass clippings, manure, and seed hulls. Inorganic mulches include volcanic lava rock, gravel, polyethylene plastic, and weed barrier fabric.
The selection of a mulch depends on its intended use. If appearance is the main goal, a rock, gravel, or wood chip mulch should be used. If soil improvement is the main goal, use straw, grass clippings, sawdust, or manure mulch that will break down and ass nutrients and tilth to the soil.
If the mulch is used to protect fall transplants by keeping soil temperatures above freezing longer into the fall apply soon after transplanting. If the mulch is to be used to reduce frost-heave and delay spring growth, apply after the ground has frozen.
Apply most mulches to a depth of 4-6 inches. Some mulches particularly loose leaves and straw, may harbor rodents. A 6-inch space should be left between these mulches and the base of trees or shrubs. If these mulches are places next to the bark of trees, rodents living in the mulch will chew the bark off the base of the tree.
As mulches decompose they tie up some of the soil nitrogen. Sometimes a quickly decomposing mulch such as sawdust can cause nitrogen deficiency that shows as a yellowing of the lower leaves. For every 100-sq. ft. of mulched area add 2 pounds of nitrogen fertilizer.
We receive many question about mulches. The only “don’t use as a mulch” is black walnut. It contains a toxic substance that keeps other plants from growing. Some mulching materials such as peat moss can be acid forming and should be used as a soil amendment more than a mulch. Pine needles are the best for winter protection from freeze injury but can be hard to get in large quantities. Straw blows easily and frequently contains weed seeds. It can be used around plants needing winter protection if anchored by mesh.
There is no perfect mulch for all occasions. Availability is usually the biggest consideration. Even If a mulch has a slight acidifying effect on the soil, lime can easily offset that condition.
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Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Director of Oklahoma Cooperative Extension Service, Oklahoma State University, Stillwater, Oklahoma. This publication is printed and issued by Oklahoma State University as authorized by the Vice President for Agricultural Programs and has been prepared and distributed at a cost of 000 cents per copy.