The Influence of Rate and Source of Nitrogen, Soil Temperature, Water Application, and Plant Growth on Certain Aspects of Strawberry Nitrogen Nutrition, and on the Form and Amount of Nitrogen Found in an Olivier Silt Loam Soil and Its Leachate
Experiments on the nitrogen nutrition of the strawberry and a typical strawberry soil in Louisiana were conducted in 1962-64 to study sources that might offer a nitrate supply more appropriate to the nitrogen needs of the plant from the time of setting in the field in the fall through fruit harvest the following spring. Sodium nitrate, ammonium nitrate, ammonium sulfate, urea, urea formaldehyde, and cottonseed meal were applied to Olivier silt loam top soil and (1) incubated in a nitrification
... tudy for 3, 7, 14, 21, 28, and 49 days at 35 and 60°F. and room temperature (mean » 80°F.), and (2) leached in a greenhouse leaching study by applying three rates of simulated rainfall in 1962-63 and two rates in 1963-64 to pots with and without plants of the Dabreak variety. Two field studies were conducted. One included the application of 68 pounds of nitrogen per acre from ammonium nitrate alone or from ammonium nitrate plus cottonseed meal at the rates of 54 and 14 pounds per acre of nitrogen respectively. The other study was the appli cation of ammonium nitrate as top-dressing at the rate of 40, 60, or 80 pounds of nitrogen per acre in single and split applications to plots of the Dabreak and Headliner varieties. Nitrate accumulation due to nitrification, though generally low, increased with increasing incubation temperatures and time. Incubation xi at room temperature gave maximum accumulation in soil samples treated with urea and ammonium sulfate. Sodium nitrate and ammonium nitrate gave the lowest accumulation while urea formaldehyde and cottonseed meal corresponded to the control (no nitrogen) samples. Only small amounts of the applied nitrogen were leached as nitrate, generally corresponding in quantity removed to the volume of water applied. Total nitrate removal was greatest from soil treated t with sodium nitrate or ammonium nitrate, both contributing large amounts in the initial leachate, and least from urea formaldehyde or cottonseed m e a l . Intermediate amounts were removed from urea or am monium sulfate treated soil. Plant growth markedly reduced the nitrate content of soil and leachate from all nitrogen sources and water treatments. Soil nitrate decreased in pots with plants with successive leachings, but increased in pots without plants. Soil nitrate in pots without plants was higher under the lower water applications. Nitrogen sources and water treatments had negligible effects on soil pH, extractable ammonia, and percent total nitrogen in plant tissue. All nitrogen sources gave significant increases in plant dry weight at the conclusion of the leaching study. Soil temperature in pots exposed to the sun on at least one side attained higher maximums than that in pots surrounded by other pots. In one field study single and split applications of 40, 60, and 80 pounds of nitrogen per acre as ammonium nitrate applied to the Dabreak and Headliner varieties of strawberries increased yields, xii decreased soluble solids, had no effect on firmness or tltratable acids, and showed variable effects on dry matter content of the fruit. Application of 68 pounds of nitrogen per acre as ammonium nitrate, compared to the same amount from ammonium nitrate plus cotton seed meal, gave a marked increase in the nitrate content of soil in the field at 30 days after application on October 1 but not at 60 days. No effects on the nitrate content at the 9-18 inch depth were noted until 60 days after application when nitrate at this depth was greater than at 0-9 inches, though not markedly different for fertilizer treatment. From March 1 through April the nitrate content at the 0-9 inch depth generally decreased but with considerable day-to-day fluctuation for both treatments.