Response of Potatoes to Rate and Placement of Nitrogen in Connecticut, 1948–1950

Abstract

AbstractSince the use of new more efficient insecticides and fungicides permits potato vines to live longer, it appeared necessary to reevaluate the response of potatoes to rate and placement of nitrogen fertilization. Such experiments were conducted on growers' fields in the Connecticut River Valley 1948–1950, located on fine sandy loam soils which had been cropped frequently to potatoes, the most common situation in Connecticut. These soils contained from 2 to 3% organic matter and had pH values of 4.8–5.5.Plots four rows wide by either 40 or 50 feet long were replicated six times in a Latin Square design. The same amount of phosphorus and potash was applied in the row in each case, namely, 180 pounds per acre. The nitrogen rates ranged from 90 to 180 pounds per acre in 1948 and 1949, and from 120 to 210 pounds in 1950.The results indicate that with the use of the best insect and disease control methods for potatoes, grown on land planted frequently to potatoes, increased yields can be obtained with increasing amounts of nitrogen up to about 150 to 180 pounds per acre in a favorable season. The use of injurious fungicides and/or inadequate insect control resulted in little or no response to more than 90 to 120 pounds of nitrogen per acre especially in years of low rainfall.During the favorable season of 1950 at locations where the moisture holding capacity of the soil was favorable or where irrigation was used on a droughty soil during dry periods, increased yields of potatoes were obtained with 180 and in some instances, with 210 pounds of nitrogen per acre over lesser amounts, on soils low in available nitrogen.There was no advantage in yields from broadcasting part of the nitrogen either in the form of castor pomace or sulfate of ammonia previous to planting, or sidedressing with ammonium nitrate as compared with putting all the nitrogen in the row, side band placement, at planting time.The study showed the availability to potatoes of applications of ammonium nitrate to furnish 50 to 90 pounds of nitrogen applied when the plants were 6 to 10 inches high. This is a less expeusive method of supplying nitrogen for potatoes.