Research at the University of Illinois shows that mulching dwarf apple trees -- with hay, straw, leaves, and the like, much of it free for the gathering during this fall period -- can double fruit yield. In fact, its benefits extend to the entire garden. For the past 20 years, says Dr. Roy K. Simons, a professor of pomology, both amateur and professional apple growers have been planting more and more dwarf trees to find answers to some serious problems of apple growers. The chief finding at the university as a result of its test plants is that the trees responded best to heavy mulching.
All gardeners should consider mulching, a technique many prefer to cultivating the soil.
A thick mulch eliminates most weeds and conserves soil moisture. A good mulch reduces by half the water lost through evaporation; moisture that is kept uniform under a mulch favors root activity in the surface soil.
In mulching dwarf fruit trees, it is essential to keep the soil surface covered to protect the shallow roots from extreme temperatures, both high and low.
The soil covering should be a moderate layer of continually decomposing material that will improve soil conditions for the root system. Mulch replenishment every two years seems adequate and, if a continual program is maintained, not too much should have to be applied at any given time.
On a slope, mulch prevents excessive runoff of heavy rains. Further, rain soaks into mulched soil more readily, because the physical condition of the soil already has been improved by the mulch. The decaying matter that works down into the soil makes it more friable and more easily penetrated by water. The soil's aeration also is improved, thus stimulating root and biological activity.
Rapidly decaying mulches, such as legume hay and ground corncobs, are much more effective than such slowly decaying ones as peat moss. A mulch will keep a heavy soil from becoming compacted when walked on soon after a rain.
Mulch also prevents root injury due to too-deep cultivation of the soil. Damage from deep tillage is far more frequent than is generally realized. Most organic farmers never cultivate more than six inches deep.
Gardeners know that the top soil is the best soil in the garden. If the top soil is turned under, it must be replenished by an abundance of fertilizer. In the absence of fertilizer, however, applications of a hay mulch provide ideal soil nutrients for all conditions.
Potash, which tends to stay near the surface of cultivated soils because the soil surface is alternately wet and dry, penetrates much deeper in a mulched soil that is more consistently moist.
Potash deficiencies are corrected most rapidly, of course, by the use of potash along with a mulch, but over a period of years hay and straw mulches will supply substantial amounts of potash as they rot.
There are many lesser benefits to mulching, such as the prevention of bruised fruit. Low-hanging vegetables and strawberries are protected from soil splashing during heavy rains. Also, in the spring, when the ground is soft and muddy, a mulch makes it possible to walk close to the plants.
To be economical and practical, the mulch used should be readily available in large quantities. Sawdust is an excellent choice if you live where it is available, and any sawdust is suitable, whether it is hardwood or softwood. Rotted sawdust is preferable, but fresh will work well if a little additional nitrogen is added to compensate for the amount taken from the soil surface as it begins to decay.
Tree leaves are probably the most common variety of mulch because they are easy to collect. If you live near a city, you just need a station wagon or truck so that you can go around and pick up the already bagged leaves on the sidewalk.
A leaf mulch conserves moisture very well; the only weed that pushes through is the persistent birdweed. Of course, if you have access to maple leaves, you will get thousands of seedlings pushing their way to the top.
Wheat, rye, and oat straws are standard mulches for strawberries. Tomatoes should nearly always be mulched. Under clean cultivated-soil conditions, tomatoes often get blossom-end rot. Mulched plants have few, if any, rotted fruits.