Almost anywhere that other things will grow, the tomato thrives—so far as soil type is concerned.

Florida grows tomatoes on coral soils that appear too poor to produce any useful crop. The fields of South Jersey are very sandy but tomatoes do well despite costly control of moisture and fertility. In some canning sections, clay loams and even clay soils are used. The ideal is a medium sandy loam, well supplied with humus for good water holding capacity. Lighter soils are generally earlier. Tomatoes on drouthy soils are likely to suffer from blossom end rot as well as from poor growth. Good drainage is required. Muck or peat soils will grow tomatoes but they are not commonly used for commercial production.

Liming is not important for tomatoes even on fairly acid soils, assuming, of course, that the very small actual calcium requirement of the plant is met. This is generally confirmed by experiments but it does not preclude the merit of lime in favoring green manure crops which, in turn, make the soil more suitable for tomatoes.

The dominant element in most sound tomato fertility programs is phosphorus with nitrogen second and potash third. Recommendations of general application are not possible but each need must be met before other beneficial additions can be fully effective.

In the home garden, a program that keeps up fertility for other crops will suffice for tomatoes. In commercial production, especially for canning, where prices received are usually low, the program must be neatly cut to fit the soil, the crop system, the value of the tomatoes and the costs of materials. A canning crop in those sections where yields are almost bound to be low, will not justify heavy investment in fertilizer. Where much is spent for irrigation, plant growing, staking and pruning, one cannot afford to curtail the fertilizer investment that will bring maximum return.

The task of this chapter is not to tell the grower how best to provide fertilizer for tomatoes but to help him in making his own plan for his own need. Research results and practical experience both contribute. One may well consult neighbors, county agent and extension specialist, as well as the many books and bulletins that are available.

Nitrogen

Nitrogen is very important to insure the growth of vine without which a good crop may not be expected. Lands vary more widely in nitrogen content than in phosphorus and potash. Sandy soils are commonly deficient in this element and often difficult to keep supplied. Here liberal applications are needed. Up to a hundred pounds [5] of actual nitrogen may prove profitable where other conditions justify. Heavier soils, well managed and manured during rotation, require less nitrogen and fair results may be obtained with no fertilizer where investment must be kept to a minimum.

Form of nitrogen to be used is largely a matter of economy though nitrate for part of it may be desirable early in the season when soil is cold and nitrification slow. Nitrate is desirable for side dressing but even here ammonia and other forms are now considered suitable when the soil is warm.

Failure to Set Fruit

Why do tomatoes sometimes run to vine with failure to set fruit? This is an old, old query and, since 1918, has been, directly or indirectly, the occasion of more research projects than any other horticultural topic. Kraus and Kraybill [6] set the ball a-rolling with a paper which called attention first to the observations of Klebs in Germany in which he emphasized the fact that external conditions influence conditions within the plant which in turn influence performance—a veritable chain of causation. Kraus and Kraybill then undertook to relate performance (vegetative growth and fruitfulness) to internal conditions, chiefly carbohydrate and nitrogen content of the plant tissues. These, in turn, were traced back to treatments applied to the soil.

They suggested four combinations of vegetation and fruitfulness in plants as follows:

1. Non-vegetative and non-fruitful. Plants whose carbohydrate supply has been cut off, say by removal of leaves which make carbohydrates. These plants were low in carbohydrate and high in nitrogen.

2. Vegetative and non-fruitful. These plants were well supplied with both carbohydrates and nitrogen. They were of the sort we describe as having "run to vine."

3. Vegetative and fruitful. These plants were well supplied with carbohydrates, but not so liberally supplied with nitrogen, thus, providing a balance between the two that was favorable for a good crop.

4. Non-vegetative and non-fruitful. These plants had ample opportunity for carbohydrate making, but were underfed with nitrogen and so could not perform well in either vegetation or fruit-making.

Kraus and Kraybill conclude that there are certain balances between these two groups of compounds—nitrogenous and carbohydrate—which determine the nature of the plant's performance—whether there will be too little vegetative growth to permit a crop, whether the plants will "run to vine" or whether they will show good growth of both foliage and fruit.

From experiments in the same field, using definite amounts of nitrate of soda per plant, Work [7] concluded that while adequate carbohydrate supply is necessary for fruiting, excess carbohydrate did not, in itself, occasion unfruitfulness but was more likely to represent an accumulation of material unused by reason of deficiency in some other factor—often nitrogen.

It was shown that nitrate of soda does not injure tomatoes until a concentration in the soil is attained which is strong enough to plasmolyze the cells, that is to withdraw water from them by osmosis. Nor were a wide variety of nitrogen and moisture and manure treatments sufficient to induce the Bonny Best variety to "run to vine." Some varieties are subject to this trouble, mostly of the large, late types.

Murneek[8] has shown that the fruitfulness of a plant may greatly affect its internal condition, its vegetative performance and its later setting of fruit. A heavy load of developing fruit, with limited soil resources, tends to limit growth and setting. Removal of fruit induces renewal of vegetative growth and of fruit setting. Failure to set fruit favors vigorous vine growth. This failure may be traceable to various causes. (1) To damage to floral parts as the blasting of the pistil by heat and drouth. Flowers of some varieties show tendency toward elongation of pistils with subsequent failure to develop normal fruit. Smith and Howlett have shown that environmental conditions as well as heredity influence this elongation. (2) To injury by insects as thrips. (3) To the character of the variety used, the Bonny group being very slightly susceptible to failure from over feeding with nitrogen while some late sorts readily "run to vine." (4) Shortage of nutrient elements as nitrogen or phosphorus or others. (5) Lack of adequate light or short day. In such cases, there may be excess of nitrogen for current need with resultant over-development of leafage. Thus, excess vegetative growth may be a result as well as a cause of poor setting.

Phosphorus

Fertilizer experiments fairly generally point to the frequency with which phosphorus is the limiting factor among nutrients in tomato production. MacGillivray[9] has studied the phosphorus content of the various parts of the plant, concluding that this element is important throughout and not alone in seed making or in rapidly growing parts as has been believed. Hepler and Kraybill[10] found some years ago and others more recently have confirmed the influence of liberal phosphorus treatments upon earliness.

Potash

The potash requirement of the tomato has not been as thoroughly studied as the requirement for the other two major elements. It is thought that potash has a part in building up sugars into more complex carbohydrates.

The consensus of fertilizer experiments suggests that potash is less important on most soils than phosphorus and nitrogen but that if these elements are in good supply, increased yields from potash are likely.

Lanham in Texas was unable to find a relation between potash fertilization and resistance to shipping hazards.

Stable Manure

Stable manure has long been recognized as useful for tomatoes. It is generally considered better to apply it to the preceding crop or at least the preceding fall than to use it just before setting of plants. If spring application is necessary, it is better to use well rotted manure. Stable manure is low in phosphorus. An approximate statement would be that 10 tons of manure is roughly equivalent to one ton of a 6-3-6 fertilizer. Thus, 1,000 pounds of 18% superphosphate would bring the analysis to 6-12-6 which would be generally regarded as a good balance.

A recent publication[11] from Pennsylvania emphasizes the value of manures and of phosphorus.

Placement and Side Dressing

Recent experiments have shown the desirability of placing fertilizer close to but not in contact with the roots of the young plants. When newly set and before new roots have developed is the time when nutrient material close at hand is needed to give the plant a vigorous send-off. Transplanters have been devised with attachments to place the fertilizer in bands at each side of the row of tomatoes and about two inches deep.

Recent experiments, notably by Sayre[12] of New York, have shown the advantage of dissolving fertilizer materials in the water used for transplanting tomatoes. One combination of materials consists of ammo-phos, 14-48, 2 parts and potassium nitrate, 1 part. Five to eight pounds of this mixture are dissolved in 50 gallons of water and about ¼ pint or ½ cup is applied to each plant, usually by the transplanting machine. There are other suitable mixtures of nutrients for this purpose. A very small investment in starter solutions has shown material increase in total yield. The practice places immediately available nutrients in the soil at the time and place to be of maximum usefulness to plants that have been severely root-pruned and have not yet had opportunity to rebuild the root system.

Another critical stage in tomato growth comes when much fruit has been set in the clusters and demands upon plant and soil are especially heavy. At this stage, side dressing with nitrogen is helpful in maintaining plant growth and providing resources for growth and maturing of fruit. On sandy or nutrient-deficient soils, more than one side dressing may be advisable. Sodium nitrate is commonly used but other materials are suitable after the soil has warmed up. Side dressing with fertilizer in solution has been recommended recently by Tiedjens of New Jersey.