The Relative Effect of Single and Fractional Applications of Soluble Nitrogen on Nitrates in Soil and Plant and on the Yields of Certain Vegetable Crops 1

The efficiency of single applications of soluble nitrogen at planting time has been compared frequently with that of fractional applications supplying an equal amount of nitrogen during the growth of the crop, but incon.sistent results make general conclusions difficult. In Table ~, a summary of 55 published trials by many workers~, 3 or more for each of ~4 different crops, shows consistent results for only 2, and further trials conceivably might produce conflicting evidence for these. It is interesting, but not conclusive, that the preponderance of evidence favors single applications for sugar beets, mangels, rye, tobacco, and spring wheat; fractional applications for cabbage, celery, corn, cotton, tomatoes, and turnips; but that for barley, oats, and potatoes there are an equal number of trials in favor of both methods of application, and nearly as many trials failed to show significant differences between the two methods. The important fact is the obvious effect of climatic and soil variations in causing variance either in the nitrogen requirements of the crop or in the rate of supply of that element by the soil. As evidence of this, Anderson and Swanback (~)4 state that fractional applications of nitrogen for tobacco first became beneficial in an extremely wet season after a series of years v~hen single applications had produced slightly better yields, and ascribe the benefit to the replacement of nitrogen lost by leaching. More recently Brown, Owenl and Tobe.y (3) state that for potatoes in Maine, "It is likely that delayed top dressing may be a wise practice during exceptional seasons,-but it is not nearly so important a problem in Aroostock County as under soil conditions where leaching is generally serious." The object of this paper is to present the results of fu)ther field comparisons of these two methods of applying nitrogen, especially for