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Cultivating and Fertilizing Potatoes

DANIEL DEAN,

Nichols, Tioga County, New York.

The problem of cultivating and fertilizing potatoes can best be considered in connection with the other factors which govern the production and marketing of the potato crop, and are very often great ly modified by these other factors.

The business of producing and marketing potatoes in any state or province is governed by the same economic laws that govern every other business. Any profitable business expands, as for example the movies, automobile and the radio. Any unprofitable business contracts, as for example the top-buggy and the windmill. Maine had only one potato crop as large as 10,000,000 bushels before 1900, this year, 47,644,000. Ida~ho in 1907 grew 13,000 acres, this year 102,000. New York state grew 441,000 acres in 1907, only 270,000 this year, although in one section of the state, Long Island, production has great ly increased in that time.

Two entirely different sets of conditions govern potato pro- duction and marketing. The first set governs the cost, and includes climate, soils, fertilizers, seed, varieties, and the costs of tillage, spraying, harvesting and marketing. The second set governs the market price the grower will receive for his finished product.

Potato production in the United States is divided into two great types, that for sale in nearby markets by wagon or truck, and that for sale by railroad or steamer to distant markets. The carlot sections have immensely increased in importance since 1900. They are those in which the cost of production per bushel is low enough to allow the payment of freight costs to distant markets and still sell in competition with local trucked in stock. In many cases the carlot areas are made up of new lands which have come into heavy production in recent years. The early crop of the southern states is nearly all shipped by rail to distant cities. The late crop carlot sections include Maine, par ts of New York, Pennsylvania and Michigan, most of Wisconsin and Minnesota, and nearly all the late crop states fur ther west.

The trucking area includes southern New England, most of New York, Pennsylvania and Michigan and part icularly the Corn Belt states f rom Ohio to Iowa. Across the southern side of this area summer heat is often too great for the potato plant to do its best and growers must often adopt different methods

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than are successfully used in the sections fur ther north where cooler summers are more favorable to the potato plant.

The price of potatoes in any consuming city in the trucking or deficiency area is set by the cost of buying them in the often distant carlot of surplus sections, plus cost of freight to the consuming city and of distribution there. In any trucking section the quantity of potatoes produced must be less than the local demand. Whenever, as in Pennsylvania and Iowa in 1928, the local production is so large that par t can on lybe sold in distant city markets in competition with the carlot area, the price for the trucked potatoes falls to the level of the price to growers in the other carlot areas. Because the potato grower in the trucking area can normally get a price considerably higher than can the growers of the carlot area, it is often pro- fitable to use expensive methods of cultivation and fertiliza- tion.

Compared with other fa rm crops, such as corn, the potato plant has a weak and tender root system. The roots are unable to penetrate well into heavy soils, which explains why potatoes seldom do well on clays. The potato plant, part icular ly at certain stages of its growth cannot stand great hea t in the soil. The southern states avoid this trouble by either plant- ing in the winter in order to mature early varieties before the extreme heat of summer, or else they plant in Ju ly and make most of the growth in the cool fall months. Although the potato plant can stand considerable drouth at times, it needs much water to produce crops of any size. Because the cash return per acre from potatoes is higher than that of most of the standard farm crops as corn, wheat, etc., the grower is justified in using cultivating and fertilizing methods that would be unprofitable with the others.

These general principles great ly change fertilizing and culti- vation methods under different conditions. One section produc- ing early potatoes will use a light, sandy soil because it warms up early in spring, will use an early variety, will plant in high ridges to warm the soil quicker and fertilize very heavily be- cause the soil fert i l i ty becomes but slowly available in cold weather. Another section within a few hundred miles may produce main crop potatoes with a variety having a long life, will use much less fertilizer, depending on the soil fert i l i ty un- loosed by the heat of the summer, and will plant on soils often very heavy. The first section sprays the crop very littIe, be- cause long life is even undesirable in an early crop. The second sprays with extreme thoroughness in order to carry the crop through the heat of the summer to the cool weather of fall. Each section is using the methods which experience has shown to be most profitable under its local condition of soil, climate and markets.

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The rotation of crops is an essential par t of crop fertiliza- tion. Because of its need of a loose, mellow soil, of abundant fertility, and of a soil retentive of soil moisture, those crops which leave the soil well filled with organic matter are best for rotation with the potato. The different legumes, the clovers, alfalfa, sweet clover and soy beans are favorites in dif- ferent sections. Selection of the part icular one to be used depends on how well it succeeds under local conditions. Be- cause the money value of potatoes per acre is considerably higher than that of most farm croPs and because of the high cost of labor and machinery, there is an increasing tendency to plow under the whole of the legume crop preceding potatoes rather than to harvest it for feeding or sale and only leaving the roots and sod for the use of the potatoes.

The general principle that potatoes need a loose and mellow soil with plenty of soil moisture governs preparation before planting. Whether fall or spring plowing or both are used, the great objective is to use the tools and methods which put the soil in this condition, the choice of tools and methods depend- ing on local conditions. After planting, the essential principles of cultivation are to prevent weed growth and to keep the soil loose and mellow as long as possible. For many years it was strongly believed that the principal reason for cultivation was to maintain a surface mulch of mellow soil which would operate to lessen loss of soil moisture through evaporation. It is now believed that cultivation is more important for pre- vention of weeds than for this purpose.

Two classes of weeds demand different methods of control. Those having perennial rootstocks such as the Canada thistle, morning-glory, quack-grass and hairy smartweed can only be destroyed by exhausting the material in the underground parts. This is most difficult, if not impossible, to do during the grow- ing season of the potato plant. I have found that with quack- grass fall plowing is absolutely necessary under central New York conditions. As soon as the soil can be worked in the spring deep and thorough disking is begun, and repeated at intervals short enough to prevent the quack-grass from getting a real start. By these methods the quack-grass plants can be repeatedly forced to s tar t new shoots and so reduce the stored plant food in the rootstocks. Jus t before planting, about June first, the soil is again plowed about ten inches deep, which leaves it very loose and mellow. Frequent use of the cultivator fur ther discourages the quack-grass until the fas t growing vines shade the soil well. Only in very wet seasons does the quack live through to injure the yield. This t rea tment has also

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el iminated Canada thistle, and reduced morning g lory to a small a m o u n t of damage.

The second grea t class of weeds is tha t of the annuals which g row f rom seeds. Any weed can be killed by tear ing it loose f rom the soil and exposing to the sun long enough. The grea t pr inciple in fighting annual weeds is to des t roy them when they are weakest . This is j u s t a f t e r the growing shoot has p a r t l y exhaus ted the store of p l an t food in the seed, and before it has had t ime to form new growth above the soil f rom which to m a n u f a c t u r e new p lan t food. Thorough t i l lage ear ly in the spr ing before p lant ing does so kill pa r t of the sprou t ing weeds, bu t it is un fo r tuna te t ha t m a n y of our wor s t weeds do not sp rou t till w a r m e r weather .

A f t e r p lan t ing the g r o w e r has two problems ins tead of one. He still has to keep s t i r r ing the soil to kill weeds, bu t he now has to r emember tha t the same tools tha t are so efficient to kill weeds will damage or des t roy the growing and tender po ta to p lan t s unless g rea t care is used. Expens ive methods of mulch ing by means of s t r a w or of pape r can be used as a subs t i tu te fo r t i l lage fo r control of weeds. Any sys tem of t i l lage m u s t be a compromise between ex t reme care to kill weeds and ext reme care to prevent damage to po ta to plants .

The tools and the methods mus t in every section be those adap ted to local conditions. Personal ly , I cul t ivate between the rows as soon as weeds s tar t , and before the po ta to p lan ts ap- pear. Because my soil is deep and wi thout a h a r d p a n so of ten found, I level down the rows j u s t before the p lan t s appea r with a leveling tool buil t fo r t ha t purpose. I t is essent ia ly a 2 by 10 p lank six fee t long set on edge and d rawn th rough the soil by two horses or a t rac tor . I t kills the weeds very well wi thout damage to the po ta to sprouts . A f t e r the p lan ts are th rough the ground s t anda rd cul t ivators and weeders are used a f t e r each rain or at in tervals of about a week. E a r l y cultiva- tion is deep, la ter ones very shal low The six-row cul t iva tor made up of a Farmal l t r ac to r and two s tandard two- row culti- va tors is very fas t and very efficient. I t is p la in tha t these methods might be wor th less under different conditions, and are only given here as an example of how one set of condit ions is met.

The most impor tan t p a r t o f cult ivat ion is to get weeds con- t ro l led so ear ly tha t it is possible to stop before i n j u r y to the growing po ta to crop. Careful exper iments have proved tha t it is f a r easier to reduce yields by cult ivat ion too la te than most g rowers can believe. Three tes ts are used by experienced growers . In New York state, a t least, the appea rance of ei ther b lossoms or of small tubers is a warn ing t ha t the p lan t s are too large to be cul t ivated more. Both are reproduc t ive pro-

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cesses tha t are exhaus t ing to the plant . The th i rd sign is in the po ta to roots. In the ear ly life of the p lan t s the roots have a tendency to drop downward in the soil. At or j u s t before blossoming a new type of roots sometimes cal led brace roots be- gins to extend in every direction j u s t under the sur face of the soil. A good tes t fo r the appearance of this t ype of roots is to wash out the sides of the hill wi th water . Dest ruct ion of these roots by late cul t ivat ion can cut the yield by one half . I t is t rue than in some season d ry wea the r in the ear ly life of the p lan ts prevents the weed seeds f rom sprout ing. I f heavy rains come when the p lan t s are a foot or more high the grower m a y have the unp leasan t choice of ei ther kil l ing the weeds by culti- vat ion tha t damages the plants , or of le t t ing the p lan ts be damaged or smothered by the weeds.

The problem of po ta to crop fer t i l izat ion is t ha t of the ne t re turn or the increased yield over the increased cos t - -whe the r the g rower shall use f a r m manures , commercial fer t i l izers o r ro ta t ion crops p lowed under to increase the yield is a quest ion to be answered under each separa te set of condit ions by the profit to be obtained f rom the use of either. In any case con- s iderable knowledge of local condit ions is needed to determine the relat ive value of ni trogen, phosphorus and po tass ium in the commercial fert i l izers, o r of the f a rm manure or the rota t ion crop.

The general pr inciple holds t rue tha t as the po ta to is a re la t ively tender p l an t compared to corn and as the acre value is high it pays be t te r than other f a rm crops fo r high fert i l iza- tion. Even the seed pota toes used may be considered to be one fo rm of indirect fer t i l izat ion. I t is well known tha t the crop yield increases when the amoun t of seed used per acre is in- creased. Many growers take advan tage of this fac t by using heavier seed in spr ings when seed is low in price. Then when seed is high in price the seed is reduced in amoun t and more fer t i l izer is used.

The use of commercial fer t i l izers on po ta toes has increased very f a s t in the eas tern pa r t of the Uni ted Sta tes in the las t th i r ty years. F r o m 2,000 to 2,500 pounds pe r acre is the s t anda rd appl ica t ion over very large areas f rom Maine south- ward along the At lant ic coast. Going wes t the quan t i ty of fer t i l izer used per acre gradually" diminishes until the point is reached where it is no longer profitable. Certified seed g rowers of ten find fer t i l izers pay be t t e r than do g rowers of table s tock because of the higher price of their product . In the pas t f ew years the use of concent ra ted fer t i l izers has increased very fas t and in t ime will g rea t ly increase the use of commercial fer t i l izers in sections where they were f o r m e r l y unprof i table because of the high cost of t ranspor ta t ion .