USDA BULLETIN No. 1190 Issued 1921, Revised 1924
How to Grow an Acre of Potatoes
written for boys and girls by William Stuart, Horticulturist
The remarkable success which has attended the efforts of those who have been instrumental in organizing and directing boys’ and girls’ club work in this country is a splendid tribute to the leaders in this movement and proof of the hearty cooperation which they have received from those boys and girls whom they have enlisted in the work. When a boy or a girl succeeds in raising a plat of potatoes yielding at the rate of 300 to 600 or more bushels per acre, as many of them have done, it is a source of inspiration to those of their club who have been less fortunate and, what is perhaps of greater importance, an object lesson to their elders as to what can be accomplished when the crop is given proper cultural attention.
If all boy and girl club members were able to produce as large crops of potatoes as have been mentioned, there would be little necessity for suggestion on “How to grow an acre of potatoes.” It is assumed, however, that many members of these clubs have at one time or another found themselves face to face with problems which they were only partially able to solve. A poor stand of plants, the presence of certain insect pests or of fungous diseases attacking different parts of the plant, or poor yields from promising-looking plants may have served to dampen the youthful ardor of some members. The aim of this bulletin is to aid those who may have been confronted with these or other difficulties to meet and overcome them more successfully, to the end that their efforts may be crowned with a well-deserved success.
INCREASED PRODUCTION DESIRABLE
The average production of potatoes in the United States for the past 10 years, 1914 to 1923, inclusive, was 99.2 bushels per acre. During the same period the State of Maine produced an average of 210.9 bushels per acre, or 112.6 per cent more than the average of the entire United States. When it is remembered that commercial yields of 500 to 600 bushels per acre are by no means uncommon in this country and that on small areas (an acre or less) much larger yields have been obtained by boys and girls belonging to agricultural clubs, one can readily see that there is plenty of opportunity for increasing the per-acre production of potatoes in the United States.
Heretofore potato production in this country has been conducted along extensive rather than intensive lines. In other words, we have been satisfied to plant twice as many acres as should have been necessary to produce a sufficient quantity of potatoes for our food requirements. Present economic conditions compel the grower to consider more seriously the desirability of reducing the cost of production by increasing the yield per acre. Increased production per acre at a reduced cost per bushel should be the goal of every potato grower in this country. The successful accomplishment of this result is dependent upon many factors, the chief of which are (1) the selection of a suitable soil, (2) the proper preparation of the soil, (3) the selection of the right varieties for the locality in which they are to be grown, (4) the planting of high-grade seed stock, (5) an abundant supply of plant food, (6) good tillage, and (7) thorough protection of the plants against fungous diseases, insects, and other pests.
SELECTION OF SUITABLE SOIL
While the potato is probably as easily satisfied in its soil requirements as any other food plant, it thrives better on some soils than on others. Gravelly or sandy loam soils are generally considered especially well suited to the production of large crops, provided they are well drained and well supplied with plant food. A very light sandy soil or a stiff clay soil should be avoided when selecting land for potatoes if large yields are desired. The ideal soil is one that does not run together in heavy rains, that works easily, that is well supplied with humus (decaying vegetable matter), and that while well drained is naturally supplied with sufficient moisture to keep the plants in a thrifty growing condition. Clover or alfalfa is generally regarded as the best preparatory crop for potato land. Either of these crops furnishes a goodly supply of humus when turned under and materially increases the moisture-holding capacity of the soil.
The economical production of an acre of potatoes is dependent to a certain extent upon its shape. For example, the longer the rows are the more economically they can be planted, cultivated, and sprayed, because long rows entail less turning and therefore less lost motion. Sixteen rows 3 feet apart and 907 1/2 feet long represent one acre and are of a suitable length to till.
PREPARATION OF THE SOIL
The land should be plowed as deeply as the character of the surface soil will permit. If the surface soil is 10 inches deep, plow it to that depth or a little more. If it is only 6 inches deep, plow it 6 1/2 to 7 inches deep. The aim should be to plow from one-half to one inch deeper than formerly, in order to increase the depth gradually and thereby augment the water-holding capacity of the soil.
Generally speaking, land that is intended for potatoes should be plowed preferably in the autumn. There are exceptions, however, to such a practice, as in the case of land that is likely to wash badly from winter rains or melting snows, or on which the crop is not to be planted until rather late in the season. In the last case it may be possible to turn under a considerable growth of clover or alfalfa by delaying the plowing until shortly before the planting season.
If plowed in the fall, it should be disked or harrowed as early in the spring as possible, in order to conserve the moisture accumulated during the winter or early spring and to prevent weed growth. The object should be to maintain a surface mulch of loose soil after each beating rain. When plowed in the spring, disk it immediately, in order to prevent the possible baking of the newly turned soil and to conserve the moisture.
In preparing the seed bed, spare no pains to fine the soil and to put it in as friable a condition as possible. To do this may require the use of a cutaway or disk harrow, a spring-tooth harrow, and a smoothing harrow, followed with a plank drag if the surface is slightly uneven or lumpy. Thoroughness in the preparation of the seed bed is as essential to the successful production of a large crop as in any other step in the process. In fact, if the crop is planted on land that is poorly prepared, no amount of subsequent cultivation will entirely remedy the defect.
PLANT FOOD SUPPLY
A maximum crop can be produced only when the soil in which they are grown is well supplied with available plant food. If a good clover, alfalfa, cow-pea, soybean, or other leguminous crop has been turned under, a much smaller application of commercial fertilizers or barnyard manures will be necessary than if the preceding crop was a grain crop. In the early truck-crop sections of the South many of the growers apply a ton or more of a 7-6-5 fertilizer to the acre. The southern truck grower tries to start his early crop as quickly as possible by using a large amount of nitrogen (usually called ammonia) to stimulate stem and leaf growth, thereby securing a strong, vigorous plant. As a rule, fertilizer applications in the South vary from 1,500 to 2,500 pounds per acre. The New Jersey, Long Island, and Maine growers use quantities equally as large as the southern growers, but with slightly different percentages of nitrogen, phosphoric acid, and potash.
An intelligent choice of a commercial fertilizer must take into consideration the previous treatment of the land and its present fertility. In fields where previous crops of potatoes have shown a tendency to scab, barnyard manure is likely to increase this disease and in such cases should be used sparingly and applied to the crop of the preceding year rather than directly to the potato crop. In the eastern and south-eastern sections of the United States it is more economical, as well as more desirable, to supplement barnyard manures with a light application of a low-grade commercial fertilizer analyzing approximately 2 per cent of nitrogen, 12 per cent of phosphoric acid, and 2 per cent of potash. If the land is known to be well supplied with potash, a 2-12-0 fertilizer will serve the purpose. The nitrogen of the fertilizer should be derived from nitrate of soda or sulphate of ammonia, which provides this plant food in an immediately available form and helps to start the plants off quickly. The high content of phosphoric acid supplies the deficiency of that element in the manure, and the 2 per cent of potash furnishes an addition of this ingredient welcome to the potato crop. When the two sources of plant food are used, an application of 10 to 12 tons of farm manure and 600 pounds of a 2-12-2 fertilizer may be depended upon to produce satisfactory results. In the West, where the soils are as a rule abundantly supplied with phosphorus and potash but are deficient in nitrogen and humus, barnyard manures supply the elements necessary to the satisfactory growth of the potato plant.
Manner of Application
It is usually preferable to apply the manure to fall-plowed land in the late winter or spring and disk it in or to spring-plowed land before plowing. Commercial fertilizers are generally applied in the drill row and well worked into the soil before dropping the seed.
When machine planters having a fertilizer-distributing attachment are used the fertilizer is distributed and the seed planted at a single operation.
The disinfection of seed potatoes was primarily undertaken for the prevention of potato scab, but it has since been found that when properly done it is also effective in destroying the resting stage of the black-scurf fungus. The disinfection of seed potatoes to free them from potato scab and black scurf is recommended as a general practice, though it will not prevent either the scab or the black scurf when it is present in the soil and the conditions are favorable for its growth. The seed should be treated before it is cut. The treatment consists in immersing the tubers for a period of from one-half to 1 1/2 hours in a cold corrosive sublimate or formaldehyde solution or from 3 to 5 minutes in a hot solution of the latter. The cold corrosive-sublimate solution is generally admitted to be more effective than the cold formaldehyde solution in destroying black scurf. The solutions are made as follows:
Corrosive-sublimate solutions. – Dissolve 4 ounces of corrosive sublimate [mercuric chloride (Hg Cl2)] in 2 gallons of hot water; then add 28 gallons of cold water. The length of treatment should vary with the condition of the seed tubers; if they are firm and ungerminated, are more or less infected with scab or black scurf, they may be allowed to remain in the solution 1 1/2 to 2 hours, but if germinated or visibly free from surface diseases the period of treatment may be reduced to from one-half to 1 hour.
Formaldehyde solution. – Add 1 point of formalin (formalin is a trade name representing a 40 per cent solution of formaldehyde gas) to 30 gallons of water for the cold solution, or 2 pints to 30 gallons of hot water. The same period of treatment is recommended in the cold treatment as that given for the corrosive- sublimate treatment. In the case of the hot formaldehyde solution the period is much shorter. With the solution heated to 125º F the time of treatment should be approximately from four to five minutes. If the potatoes are treated in bulk – that is, loose – it is recommended that on removal from the solution they should be piled up and covered with a blanket or burlap sacks for an hour, after which they should be spread out to dry. If the tubers are sprouted, shorten the time to 3 to 4 minutes.
Corrosive sublimate is an extremely poisonous substance, and every precaution should be taken to prevent farm animals from drinking the solution. Care should be exercised in the use of the vessels afterwards to see that they are thoroughly rinsed out. Being a metallic substance which readily attacks metals, only wooden, earthen, or concrete vessels can be used safely. Owing to the fact that a considerable quantity of the corrosive sublimate is absorbed by the tubers and the containers in which they are placed, the strength of the corrosive sublimate is quite materially reduced with each treatment; hence it is necessary to renew the solution after three or four lots have been treated in it. This makes it a little more troublesome and expensive than the formaldehyde treatment, for the strength of the latter is not diminished. Seed potatoes, to be effectively treated, should be as free from dirt as possible. The newly treated seed should be spread out to dry as soon as removed from the solution.
QUANTITY OF SEED
Low yields are frequently due to the use of seed too sparingly. According to the Bureau of Agricultural Economics, the average quantity of seed used by the growers of the United States in planting an acre of potatoes is 8.6 bushels. It is believed that better yields would be obtained if from 15 to 18 bushels of seed per acre were used; in fact, under certain conditions there is every reason to suppose that a still larger quantity would be found profitable.
SIZE OF SEED
As a result of many experiments, it has been shown rather clearly that a good-sized seed piece is preferable to a small-sized one. A seed piece containing from one to three eyes and weighing from 1 to 2 ounces (fig. 3) will, if properly spaced, say, 12 to 14 inches, give better results than smaller sized pieces cut to single eyes (figs. 4 and 5). The small-sized seed pieces are more liable to rot if the ground is cold and wet after they are planted and before they have germinated, and they are also more likely to dry up and fail to germinate if the ground is very dry or is poorly prepared. The smaller the size of the seed pieces used, the more thoroughly must the seed bed be prepared and the more favorable must be the growing conditions between the dates of planting and actual germination in order to secure satisfactory results.