As soils and methods of soil treatment vary greatly on different farms where tomatoes are grown, it is useless to attempt much more than a general discussion of this subject. There is an antiquated idea that the tomato should not be planted in rich soils. This wrong conception of the needs of the plant has perhaps had its origin in improper methods rather than in actual tests of liberal and intelligent feeding. Every observing grower is familiar with the injurious effects of large amounts of soluble nitrogen, applied late in the season, or of fresh stable manures used shortly before planting. Such treatments, especially if there is a shortage of the mineral elements, invariably result in a heavy growth of vine and foliage and a light crop of small fruits. While nitrogen is essential, it should be used in moderation. Its value is greatest early in the season, before the organic forms have had time to be changed by nitrification into nitrates. Numerous experiments show the value of spring applications of nitrate for this crop. Such treatment encourages a vigorous vine growth before the fruits begin to color and in most instances has been the means of increasing the yield. Notwithstanding the beneficial results arising from the use of nitrate of soda, it is admitted that part of the nitrogen should be derived from an organic form, as dried blood, tankage and fish scrap. For the late crop the soluble forms of nitrogen are not so useful, and yet in thin soils they may be employed to advantage.
The mineral elements must also be supplied in ample quantities, for without them the fruits will be small and inferior and the crop light. There should be a proper proportion of the three elements applied. This will doubtless vary greatly in different soils, or even on the same type, the amount of each to use depending upon previous methods of cropping and of soil treatment.
A knowledge of the composition of the fruit and the vines assists in the determination of a satisfactory combination of fertilizing ingredients. Voorhees ("Fertiliz-ers," p. 233) estimates a ton of the fruit and vines to contain the following amounts of nitrogen, phosphoric acid and potash:
Phosphoric acid lbs.
Vines (green) ...
He estimates that a yield of 10 tons an acre, with vines of probably four tons, would contain 57 pounds of nitrogen, 16 of phosphoric acid and 94 of potash.
Because the requirements of soils vary widely, Corbett (Farmers' Bulletin, 220, U. S. D. A., p. 11) recommends the following simple fertilizer test:
Plot 1. Nitrate of soda, l/2 pound to 10 plants. Plot 2. Muriate of potash, 1/2 pound to 10 plants. Plot 3. Phosphate, 2 pounds to 10 plants. Plot 4. Nitrate of soda, 1/2 pound; muriate of potash, pound to 10 plants. Plot 5. Phosphate, 2 pounds; muriate of potash, 1/2 pound to 10 plants. Plot 6. Nitrate of soda, 1/2 pound; phosphate, 2 pounds to 10 plants. Rot 7. Nitrate of soda, 1/2 pound; phosphate, 2 pounds; muriate of potash, 1/2 pound to 10 plants. Plot 8. Barnyard manure, I shovelful to the plant. Plot 9. Unfertilized. A careful record should be kept of the fruits from each plot.
On thin soils rotten manure is often used. It increases the size and the yield of the fruit. It is frequently applied in hills or furrows.
The most successful growers of early tomatoes use fertilizers carrying about 4 per cent nitrogen and 8 to 12 per cent each of the mineral elements. Amounts vary from 500 to 1,000 pounds an acre. In good soils the percentage of nitrogen may be reduced to 2 per cent. A smaller proportion of nitrogen is generally an advantage for the late crop.