Utilization of ammonia supplied to peaches and prunes at different seasons

Abstract does not appear. First page follows.

Nitrogen fertilization of peaches and prunes in the fruit-growing area of Sutter County, California, has become a well-established practice. Earlier trials and commercial experience have fairly well defined the profitable rates of application for peaches. Responses by prunes are common but not universal in the area. There has been some doubt concerning the relative effectiveness of equal amounts of nitrogen applied at different seasons. This question has now assumed more prominence because of the practice of applying ammonia in the irrigation water as either a summer or a fall treatment. To obtain information on this point, experimental plots of peach and of prune trees were established in 1938.

Peach Experiment

A series of plots was laid out in a Paloro peach orchard on Gridley loam, the prevailing soil type in the orchards of the county. The soil is shallower than the best of this series. The orchard was planted in 1924.

Ten plots of 60 trees each were arranged as shown in figure 1. The form of the plots, 4 trees by 15, was adapted to the orchard practices. Trees were planted 20 feet apart each way. Irrigation was by rectangular basins, and all treatments received the same amount of water. Orchard practices were typical of the district. The outside trees—that is, 4 at each end of each plot—served as guards.

Methods

Nitrogen was applied to all plots except checks at the rate of 1 pound annually per tree. Ammonium sulfate, (NH₄)₂SO₄, was put on plots 5 and 10 during the first week in January each year. Anhydrous ammonia, NH₃, was distributed in the first irrigation to plots 1 and 9; in the last irrigation to plots 4 and 6; and half in the first and half in the last irrigation to plots 2 and 7. Plots 3 and 8 were checks. Nitrogen deficiency was so acute in plots 3 and 8 that one application was given them in 1939. The dates of the first irrigation varied from year to year—from May 29 in 1939 to June 25 in 1942. Those of the last irrigation varied from September 8 in 1940 to October 25 in 1939.