At the end of the three years the plant food account will balance up with:
| Nitrogen | a gain of 2 pounds. |
| Phosphoric Acid | a loss of 16 pounds. |
| Potash | a loss of 22 pounds |
This result is of course approximate. There will be some loss of nitrogen through leaching and denitrification. Some of the potash and phosphoric acid will be converted into unavailable forms. This can be made good by applying to the cotton a fertilizer containing twenty pounds of nitrogen, sixty pounds of phosphoric acid and twenty pounds of potash.
Additional nitrogen and organic matter can be grown to turn under by planting crimson clover in the cotton at the last working for a winter cover crop to be turned under for the corn, and by planting cowpeas or soy beans between the rows of corn.
If this is done it may not be necessary to add any nitrogen in the fertilizer, letting that supply only phosphoric acid and potash.
If commercial fertilizer is used on the cotton, it would be a good plan to apply the manure from the stock to the corn.
To follow our crop on Field 1 through the three years we will have, first, cotton drawing large amounts of plant food from the soil and diminishing the humus of the soil.
Growing a winter crop of crimson clover, turning back all the cotton refuse except the lint and oil, and applying the barn manure will furnish ample plant food for the corn and replenish the organic matter.
The corn is a rather stronger feeder of phosphoric acid than cotton and will be able to get sufficient from that left by the cotton.
The oats will be able to get a full ration after the corn, and the cowpeas will readily take care of themselves on the score of plant food and will put the soil in fine condition for cotton again.