I enjoy looking back at plant history and seeing how things have changed. Weeds continue to be a battle almost 60 years later. Here is an article published in 1952 to show what they were doing back then.
Weeds – man’s opponent since he first grew crops—are loosing the fight. With the discovery of 2-4-D for broad-leaf weed control, a tremendous new research program began sounding the death knell for all weeds. Our accumulated store of knowledge, plus improved equipment and techniques, make the possibilities of weed control with chemicals appear unlimited.
At first research was directed towards the destruction of established weeds. But more attention is being directed towards killing weeds with chemicals in the very early stages of growth. This approach is logical because less chemical is required to kill small weeds and the early control of weeds removes a source of competition for moisture and nutrients. Now, we go still further and destroy weeds before or at the time the crop is planted.
Time and expense are required to remove weeds by hand or cultivation from seedbeds, newly planted turf, gardens and field crops. It’s a great improvement, therefore, to he able to either kill weed seeds directly or the seedlings shortly after germination. Some materials which have been used for this purpose add fertility to the soil, in addition to saving much time and money in weeding and maintenance.
One chemical has repeatedly shown outstanding promise in newly prepared seedbeds in the Northeast. It is a material known chemically as granular calcium cyanamide and commercially as cyanamid. In the granular form, calcium cyanamide contains 20 per cent nitrogen and the equivalent of 70 per cent hydrated lime. When the weed destroying capacity is considered with the fertilizer value of cyanamid, this chemical becomes a versatile material.
How is cyanamid used to destroy weed seeds? Several methods have been found practical. but the following simplified procedure is quite satisfactory. Apply 50 pounds of cyanamid uniformly over every 1,000 square feet of newly prepared seedbed. The term “newly prepared seedbed” implies that all preparations of grading and leveling have been completed. Since 50 pounds of cyanamid will supply 10 pounds of nitrogen, no additional nitrogen should be applied to the seedbed; some phosphorus and potash will be needed, however. Approximately six pounds of superphosphate and 1% pounds of muriate of potash will, with the 50 pounds of cyanamid, give the ingredients of a complete fertilizer. The superphosphate and potash are mixed with the upper 2 to-3 inches of topsoil. Unless a soil test shows that the soil is very acid with a need for more than 48 pounds of limestone, which is equivalent to tile amount of calcium contained in the cyanamid, this material can be omitted when preparing the soil.
When these operations are complete, cyanamid is broadcast over the surface of the seedbed at the previously mentioned rate. Do not apply it in bands. Spreaders which will distribute the material evenly are available. Cyanamid can he left undisturbed on the soil surface or it can be raked lightly into the upper topsoil. If the seedbed is on a slight slope the cyanamid should be raked in.
Seeds should not be sown until about four weeks after the soil has been treated with cyanamid. If the seedbed becomes dry during this period it will be necessary to apply water, wetting the soil to a depth of 3 or 4 inches. This does not mean to hold the hose or sprinkler in one spot until puddles form over the surface, but rather, to water slowly allowing the water time to penetrate the soil.
When the seedbed is ready for seeding, rake only the upper 1/4 to 1/2 inch of topsoil to provide the germinating layer for the seed. When the area is seeded, roll it lightly.
An adaptation of this method is to apply 25 pounds of cyanamid to each 1,000 square feet of soil, raking it into the upper inch or two of prepared seedbed. The same amount of superphosphate and potash previously recom• mended with 50 pounds of cyanamid is also applied at this time and cultivated in with the cyanamid. When this is dotie, broadcast another 25 pounds of cyanamid on the surface and rake it lightly into the topsoil. -A waiting period of about four weeks is required to make sure the toxic effect of the cyanamide has dissipated before tile area is seeded. Moisture should be added if the soil becomes dry during the waiting period.
The importance of weed-free seedbeds cannot be over emphasized when lawns are seeded in late spring and early slimmer. The success or failure of a seeding at this time depends largely on whether weeds are controlled or allowed to compete with the young grass seedlings for food and moisture.
This cyanamid method of weed control is also useful for late summer or early fall seedings. The treatment should he planned far enough in advance to allow for a four-week waiting period after treatment. If this is done, the seedbed can be seeded in time to take advantage of the early fall growing season.
Cyanamid has been found useful in controlling weeds in tobacco and vegetable seedbeds, as well as in new putting greens and fairway and lawn turf. It is being studied now as a treatment for the control of weeds in soil newly planted with corn and as a pre-seeding treatment for legume-grass plantings. Nurserymen may find it useful in seedbeds for crops which require hand weeding or hoeing.
The study of weed control in seedbeds is not limited to cyanamid. Many other chemicals which can he applied in the same manner have been tested. Those which have given good to excellent control of weeds are: ammonium thiocyanate at two to four pounds, 2,4-D at one-eighth pound and one-half gallon of PMAS (phenyl mercury acetate) to ten gallons of water, all per 1,000 square feet of soil. PMAS is a turf fungicide and may be effective against such seedbed diseases as damping-off and seedling blight. A waiting period of from two to four weeks before sowing seeds should he observed with these materials, as with cyanamid. Soil moisture must also be maintained.
Chemicals can be used to destroy weed seeds in compost. Clean compost, free of viable weed seeds, is essential for top-dressing putting greens, grass tennis courts, howling greens and other fine turf areas and for use in seedbeds and greenhouses. Calcium cyanamide is very effective in destroying weed seeds in compost, Other materials will kill the seeds but have not proven as useful from a practical standpoint.
Treating compost with cyanamid is a simple job. After the compost has been prepared and passed through a 1/4-inch mesh screen. 13 pounds of cyanamid should be thoroughly mixed with each cubic yard of screened compost. At the time of mixing the compost should contain from 15 to 20 per cent moisture. In other words, it should he slightly moist, but not wet and sticky. Once the compost has been treated with cyanamid a waiting period of from four to six weeks is usually required before the compost can he used. During this period the cyan-mid becomes active and kills the seeds in the compost. If the compost is used before this action is completed, it may burn or discolor the lawn.
A satisfactory method is to prepare the “cyanamized” compost during early fall months and store it in bins for use the following spring. Enough of this mixture can be made at one time to provide sufficient compost for the complete growing season.
If cyanamized compost is to be used satisfactorily, a few precautions should be followed. Do not apply this mixture on wet grass. The compost will adhere to wet foliage and cause burning. And do not leave the grass completely covered with a pile of compost for any extended period. As the compost is spread on the grass it should be worked down between the blades with the hack of a wooden rake or with a steel door mat used as a drag.
The grass will take on a pleasant rich green appearance shortly after the corn-post is spread on it. This is largely due to the nitrogen content of the compost. The amount of nitrogen and calcium supplied by the compost should be taken into account in the fertilizer program. On the basis of applying one-quarter cubic yard of compost on 1,000 square feet of lawn, there would be approximately one-half pound of nitrogen and the equivalent of three pounds of limestone added. Weed-free cyanamized compost is a tonic to turf.
Cyanamid can also be used in field preparation of compost. If the top-soil needs additional treatment to improve the texture, that should be done before the cyanamid is applied. Often some form of organic matter or compost and sand are used to alter and improve the soil. When these operations are complete, mix cyanamid into the upper 2 or 3 inches of soil at the rate of 50 to 75 pounds to 1,000 feet. A waiting period of four to six weeks will give the cyanmia time to break down and destroy the weed seeds. This method of field preparation of compost is somewhat similar to the preparation of a weed-free seedbed.
Sterilizing soil with fertilizers or chemicals appears to be a very practical method of controlling weeds and fertilizing seedbeds in one simple operation.
