The nitrogen content of grasses as influenced by kind, frequency of application, and amount of nitrogenous fertilizer

A study of the effects of various sources of nitrogen and frequencies and rates of application of calnitro on the nitrogen content of Kentucky bluegrass and Rhode Island bent grass was made for 1936 and 1937. The results are summarized as follows: 1. Of eight nitrogen carriers applied to pure stands of Kentucky bluegrass and Rhode Island bent grass, ammonium carbonate alone failed to give significant increases in total nitrogen over the untreated plats. In this respect there were no appreciable differences between the other seven sources of nitrogen. 2. The data on frequency of application of calnitro show that marked increases in total nitrogen in both grasses occurred only in the first cutting after the fertilizer was applied. After about a month, the influence of the calnitro was no longer manifest. 3. A single application of nitrogen in April produced its greatest effect in May, after which the nitrogen content fell rapidly and remained low for the rest of the season. By withholding the fertilizer until June or August, the highest point in total nitrogen for the season was reached in the succeeding cutting. However, a relatively high rate of nitrogen application (56 pounds) was required to attain this end. 4. In regard to amount and frequency of applying nitrogen, 14 pounds applied, six times during the season produced practically the same increase in average nitrogen content over no treatment as three applications of 28 pounds. However, there was less fluctuation when applications were made six times per season. When 56 pounds of nitrogen were applied three times (168 pounds per season), further increases of 0.39% in the case of Kentucky bluegrass and 0.32% in the case of Rhode Island bent were obtained in the average contents of nitrogen. 5. The percentage recoveries of nitrogen indicated that calnitro, calcium nitrate, ammonium sulfate, and sodium nitrate were more efficient than the other four carriers. When calnitro was applied at different times during the season, the greatest recovery was obtained from the plats receiving nitrogen only in April. August nitrogen was the least efficient, with June intermediate.