Is your lawn thin, weedy, or moss-infested? Do you find it impossible to grow grass under shade trees? Have you tried sowing this seed or that with no results other than a bright green cover for a few months, which is then gradually taken over by weeds?
Don’t be discouraged if you have had one or more of these experiences, for there is a remedy for each. Indeed, the ideal feeding program—namely, the right amounts of plant food consistently applied at the right time over the years—can accomplish renovation miracles.
It gives maximum encouragement to the permanent grasses in your lawn and maximum discouragement to weeds.
Such a program is particularly effective when accompanied by attention to soil aeration, surface and subsurface drainage, deep subsurface feeding of shade trees, and proper year-round maintenance practices (mowing. watering, weed-killing, rolling, etc.).
Essential Food Elements Of Plants
But first, let’s look at the essential food elements that all plants must take from the soil for proper growth. These are:
- Nitrogen (N)
- Phosphorus (P)
- Potassium (K)
Numerous other elements are needed in much smaller quantities. The latter is present in most good soils and commercial fertilizers and exists as impurities or added “trace elements.”
But since nitrogen, phosphorus, and potassium are needed by plants in relatively large quantities, these almost invariably must be added to the soil to “feed” the plants. Therefore, it is around these three elements that dozens of fertilizer formulae have been developed to meet specific crop needs or to correct unusual soil deficiencies.
Minimum Percentage Content
Every bag of fertilizer carries a label giving the minimum percentage content of nitrogen (N), phosphorus as phosphoric acid (P..05), and potassium as potash (K,0).
These percentages. consistently listed in this order, are referred to commercially as the “grade.” Thus, a 4-12-4 grade fertilizer contains 4% percent nitrogen, 12% percent phosphoric acid, and 4% percent potash.
A 10-6-4 grade (used on lawns, golf courses, parks, and another well-groomed turf) contains 10% percent nitrogen, 6% percent phosphoric acid, and 4% percent potash.
Because the nitrogen carriers are the most expensive part of fertilizers, the 10-6-4 grade costs more per pound than the 4-12-4, although each contains 20 units of plant food.
However, to get corresponding quantities of nitrogen (and consequently corresponding shoot and leaf stimulation), only 40% percent as much fertilizer needs to be bought and applied on lawns when 10-6-4 is used as when 4-12-4 is used.
Because nitrogen is essential to leaf production, it is of utmost importance in feeding lawns, for the leaves are constantly removed by mowing. (If lawn clippings are not so heavy that they will smother the grass, permit them to remain on the lawn; they return needed food and organic matter to the soil.)
Years ago, the United States Golf Association Green Section by analyzing clippings from specific lawn areas. They demonstrated that as many as 5 pounds of nitrogen could be removed annually in clippings in front of 1,000 square feet of turf grass.
The same clippings removed only 2 pounds of phosphoric acid and 1 pound of potash. In addition, when nitrogen is available to plants, it is readily soluble in water and is easily washed out of the soil. Consequently, it has little hold-over effect from one year to the next.
Plants and Nitrogen Relationship
Two meaningful relationships exist between plants and nitrogen, which may help you plan a more effective and economic lawn-feeding program.
First, although nitrogen is essential to good leaf production, it delays or even prevents flower and fruit production when it is added to soils in large amounts. This is highly desirable on a lawn but certainly not in the rose garden or corn patch.
Therefore, fertilizers for flowers and most vegetable crops carefully avoid excess nitrogen. They are high instead in phosphoric acid, which stimulates flower and fruit production as well as good root growth.
The second significant nitrogen-plant relationship is that nitrogen is available to plants in two water-soluble forms:
- Nitrates (NO3)
- Ammonia (NH3)
Many crop plants, white clover, and lawn weeds prefer nitrates, but grass plants thrive on ammonia nitrogen.
Therefore, by applying fertilizer in which at least part of the nitrogen is in the form of ammonia, it is possible to feed the grass and discourage the weeds.
But such a program also prevents clover. So should you want white clover on your lawn, you may have to reseed the clover occasionally if you use ammonia nitrogen over the years.
Phosphorus
Grass needs phosphorus, the second element in plant food formulas, to make good root growth. Phosphates do not leach out of the soil, as does fertilizer nitrogen. On the contrary, at the first point of contact with the ground.
Phosphates are likely to be “fixed” as relatively insoluble calcium, magnesium or iron phosphates by chemical reactions with other salts of these elements. Therefore, a relatively small amount of phosphate applied annually in a fertilizer is usually sufficient to promote excellent grass growth.
Potash
Potash, the third element in chemical fertilizers, is necessary for all plant growth processes. It is present in most soils, except very sandy ones, in quantities adequate for grass growth. Therefore, only small amounts of potash, if any, must be present in your fertilizer.
They are making use of these facts and principles. All lawns should be fed preferably with a high-nitrogen fertilizer during the season when grass plants are about to make maximum growth.
In sections where bluegrass, fescues, and bent grasses predominate, lawns should be fed in late summer (before the September equinoctial storms).
These grasses grow best when nights are cool and days warm—in spring and fall. Late-summer applications are generally better than spring ones because annual summer weeds and weedy grasses, such as crabgrass, die with the first frost.
This gives well-fed grass all fall and spring to produce a turf sufficiently dense to resist reinvasion the next May by the summer weed annuals. (Exception: In the North, lush autumn growth should not be encouraged by fall fertilizing if the trouble is to be expected from snow mold.)
You can also fertilize bluegrass, fescues, and bent grass in late winter while the ground is frozen and the lawn can be walked on without injury. In addition, this application makes food available for early growth during the first warm days.
Spring Fertilizer Application
Fertilizer applied later in spring, however, merely feeds crabgrass and annual weeds, which are too prone to take over when the turf grasses become semi-dormant during hot summer weather. Therefore, spring feeding of lawns must be avoided where crabgrass is a problem.
However, in southern states, where Bermuda grass, Zoysia, centipede grass, and other subtropical grasses compose the lawn, spring is the time to fertilize. This is because these grasses make their maximum growth in hot weather and should be fed just before that new growth.
If you overseed in the fall with ryegrass for a green winter cover (as may be done with Bermuda grass lawns), fertilizer should again be distributed along with the ryegrass seed.
We’ve already established that a high-in-nitrogen commercial fertilizer (also proper, of course, of organics) is best for lawns. But how much should you use, and what about the various grades?
At least 2 pounds of nitrogen should be fed to every 1,000’ square feet of lawn yearly, at most 1 pound in one application. This would mean 20 pounds of a 10-6-4 mixture, 40 pounds of 5-10-5, or 50 pounds of a 4-12.4 grade.
If you use one of the newer highlighters, good ones that contain a high proportion of nitrogen are activated sludge, cottonseed meal, or soybean meal. All three of these have approximate analyses of 6-3-2.
Bonemeal
Bonemeal is not so desirable for established lawns because although raw bonemeal may contain as much as 5% percent nitrogen, it has approximately 23% percent phosphoric acid.
The advantages of the organics are that the risk of burning the grass is much less than inorganic forms, and the nitrogen is not leached away from the soil so rapidly.
The disadvantage of organics is that nitrogen is only available to the plants after fertilizer distribution, as is the case when inorganics are used. So the grass cannot be stimulated as rapidly to take advantage of seasonal growing conditions.
If an inorganic fertilizer is your choice, observe the precautions in the box on page 87.
Final words of advice: Never sow seed (on a few bare spots or over an entire lawn) without applying fertilizer. Remember that fertilizer is as essential as seed in maintaining established lawns.
44659 by Fanny-Fern Davis