A concrete illustration may bring out the philosophy underlying farm schemes better than abstract problems.
The following outline shows a five-course rotation with the method of fertilization which the results of the Pennsylvania Station indicated would be advisable, at least on limestone soils in eastern United States.
| 1. Maize | yard manure, 8 tons per acre. |
| 2. Oats | nothing. |
|
3. Wheat |
acid phosphate, 350 lbs. muriate of potash, 100 lbs. |
| 4. Clover and timothy | nothing. |
|
5. Timothy |
nitrate of soda, 150 lbs. acid phosphate, 150 lbs. muriate of potash, 50 lbs. |
This rotation is suggested for the purpose of maintaining a farm that is already in a fairly fertile condition and one on which there is no considerable amount of purchased feed. Where concentrates are purchased liberally, yard manure should be available to use on the timothy and meadow in place of the commercial fertilizers.
Where there is plenty of manure and it is desired to increase the amount of maize and hay and reduce the amount of oats and wheat, the following rotation and method of fertilization would be indicated:
| 1. Maize | acid phosphate, 200 lbs. |
| 2. Maize | yard manure, 8 tons. |
| 3. Oats | nothing. |
|
4. Wheat |
acid phosphate, 350 lbs. muriate of potash, 100 lbs. |
| 5. Clover and timothy | nothing. |
|
6. Timothy |
nitrate of soda, 150 lbs. acid phosphate, 150 lbs. muriate of potash, 50 lbs. |
| 7. Timothy | yard manure, 8 tons. |
Where there is plenty of yard manure, it would be also applied to maize under No. 1, or the yard manure could be applied to maize under No. 1, and commercial fertilizer applied to timothy under No. 6 could be repeated under No. 7. If the land is more or less depleted, an application of 200 pounds of acid phosphate to the oats would be advisable. However, the purpose is not to prescribe exact methods, but to point out underlying principles and their possible application.
As further illustration, it seems probable that the practice of a market gardener in using excessive amounts of stable manure might, in some instances at least, be modified to good advantage by reducing the amount of manure and increasing the amount of commercial fertilizer used. Unfortunately there is no experimental evidence bearing upon this question.
Potash required to maintain fertility is largely to be found in the coarse fodder, such as hay, maize stover and silage, and in the straw used for bedding; hence where these substances are used in abundance and returned to the soil the amount of potash required to be supplied in fertilizers is reduced to a minimum. Where, however, the amount of live stock is limited and the products sold contain large quantities of potash, such as hay and straw, the supply furnished in fertilizers must be liberal.
Phosphoric acid is always being slowly depleted from the soil either from the sale of farm crops or animal products. There is no way of returning this loss completely, except from the addition of a commercial fertilizer.