Table II.—Average Increase in Grape Yields and Average Financial Gain from Fertilizer Applications
N = nitrogen, P = phosphorus, K = potassium, Ca = lime.
Gains in tons per acre.
| N, P, K, Ca. | N, P, K. | N, P. | N, K. | P, K. | |
|---|---|---|---|---|---|
| Tons | Tons | Tons | Tons | Tons | |
| First plat of pair | 3.51 | 3.96 | 3.83 | 3.87 | 3.39 |
| Second plat of pair | 4.10 | 4.02 | 3.97 | 4.18 | 3.61 |
| Average | 3.80 | 3.97 | 3.90 | 4.02 | 3.50 |
| Check plat | 3.12 | 3.12 | 3.12 | 3.12 | 3.12 |
| Average gain | .68 | .85 | .78 | .90 | .38 |
| Average financial gain | $5.82 | $13.84 | $14.05 | $18.54 | $6.99 |
From this last table the benefit from nitrogen appears quite evident since every combination in which it appears gives a substantial gain over the one from which it is absent. Phosphorus and potassium without the nitrogen, lead to only a slight increase over the check; and lime appears to be of no benefit. Financially, the complete fertilizer and lime combination, the nitrogen and phosphorus combination and the phosphorus and potassium combination failed to pay their cost in five of the ten comparisons; the complete fertilizer was used at a loss four times out of ten; and the nitrogen and potassium combination three times out of ten. Lime had no appreciable effect on either vines or fruit.
"No effect of the fertilizers on the fruit itself, aside from yield, was shown for the first three years; but in 1912, and even more markedly in 1913, the fruit from the plats on which nitrogen had been used was superior in compactness of cluster, size of cluster and size of berry. In 1912 also, when early ripening was a decided advantage, the fruit on the nitrogen plats matured earlier than that on the check plats. In 1913 the favorable ripening season and the smaller crop tended to equalize the time of ripening on all plats. The grapes on the phosphorus-potassium plats were better in quality than those in the check plats but not as good as those on the plats where nitrogen was used.
"Other indexes also show plainly the benefit from nitrogen in this vineyard; for size and weight of leaf, weight of wood produced and number of fruiting canes left on the vines were all greater where fertilizers, and particularly nitrogen, had been used. The three-year averages (1911–1913) of the measurements for these characteristics are shown in [Table III]:
Table III.—Comparative Production of Leaves, Wood and Fruiting Canes on Grape Vines Differently Fertilized
(Averages for three years.)
| Fertilizer Application | Leaf Weight[11] | Wood Pruned[12] | Fruiting Canes Left[13] |
|---|---|---|---|
| Grams. | Lbs. | ||
| Complete fertilizer; lime | 1,033 | 1,295 | 2,468 |
| Complete fertilizer | 1,010 | 1,367 | 2,609 |
| Nitrogen and phosphorus | 1,047 | 1,272 | 2,585 |
| Nitrogen and potassium | 1,069 | 1,401 | 2,646 |
| Phosphorus and potassium | 964 | 1,086 | 2,326 |
| Check | 930 | 915 | 2,110 |