The use of small amounts of nitrogen for corn in addition to phosphorus and potassium

1. The present study compares the prevalent practice of using complete fertilizers for corn with the use of similar fertilizers from which the nitrogen has been omitted and in which only the phosphorus and the potassium have been included. The fertilizers were applied in the rows or near the hills at planting time at rates which applied only 2 to 6 pounds of nitrogen per acre. 2. The results reported are for 23 experiments of 1 to 9 years duration on most of the important corn soils in Indiana. The 23 experiments permit 261 comparisons of PK with NPK fertilizers. 3. The nitrogen resulted in an average decrease in yield of 1.8 bushels of corn per acre. The odds indicate a high significance for the decrease. 4. The nitrogen used at planting appears to have decreased the corn yield largely or entirely regardless of (a), season; (b), soil texture; (c), the yield levels; (d), the use of manure for the corn; (e), side-dressings with nitrate of soda during the growing season; or (f), whether 2, 3, 4, or 6 pounds of nitrogen were applied at planting. 5. When the corn followed clover or alfalfa, the nitrogen effect was somewhat more favorable or less unfavorable than otherwise. 6. In eight instances comparisons were made between the effects of small and larger amounts of nitrogen. In these cases an average of 3 pounds of nitrogen reduced the yield 1.8 bushels, while an average of 9 pounds increased the yield 2.5 bushels compared with PK only 7. Limited data indicate that organic nitrogen carriers were slightly superior to inorganic carriers. 8. Phosphate-potash fertilizers considerably hastened the early growth of corn. The addition of nitrogen produced only a relatively small further increase in early height. 9. Nitrogen had little or no effect in hastening maturity. 10. In conclusion, it appears that for use with corn at planting, at least in Indiana, phosphate-potash fertilizers are preferable to fertilizers containing nitrogen in addition. This is the case when less than 6 pounds of nitrogen are applied per acre. Further research is needed to determine whether any rate, method, or time of applying nitrogen for the corn crop will be profitable.