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].
