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NITROGEN FERTILIZER ON CRESTED WHEATGRASS

Plots Fertilized Every Year:
Table 8 gives the hay yields from old crested wheatgrass plots which have been fertilized every year with ammonium nitrate (33-0-0). This trial was begun in 1955 and 11 year's data are available from it. Throughout the trial the fertilizer has been applied in early spring, generally in early to mid-April. Treatments on the plots include check (no nitrogen), 25 pounds nitrogen per acre, 50 pounds, and 100 pounds.

Excellent yield responses were obtained in the 1965 season. The yield of 4,267 pounds of hay (oven-dry weight) obtained with 25 pounds of nitrogen per acre was the highest for this rate of application obtained during the 11-year period of the trial. Yields in 1962 and 1963, however, were almost as good. Slightly better yields were obtained in the 1963 season with the 50 and 100 pound rates than in the 1965 season. The production of the check in the 1965 season was 2223 pounds per acre, compared to the 11-year average of 1418 pounds per acre. Check yields in 1962 and 1963 were slightly better than the 1965 check yield.

All rates of application resulted in the production of a ton or more of additional hay above the check yield. Thus all three rates of application would have been profitable, with nitrogen figured at .10 per pound and hay valued at .01 per pound. However, the first 25 pounds of nitrogen produced the major boost in yield, and would have been the most economical rate of application. The 11-year average yields of 2,225 pounds per acre for the 25 pound rate, 2,419 pounds with the 50 pound rate, and 2,432 pounds from the 100 pound rate clearly show that there is no justification for the use of the 50 and 100 pound rates over a period of years. The average increment of production per 25 pound increment of nitrogen is relative small after the first 25 pound application.

Table 8. Forage Production from Old Crested Wheatgrass Plots Fertilized Annually at Three Rates of Nitrogen (33-0-0).
Year Check Dry Weight Yield-Lbs./Acre Percentage Increase Over Check
25 Lbs. N 50 Lbs. N 100 Lbs. N 25 Lbs. N 50 Lbs. N 100 Lbs. N
1955 1276 2096 2121 2494 64.3 66.2 95.4
1956 612 751 763 670 22.7 24.7 9.5
1957 1356 2117 2064 2174 56.1 52.2 60.3
1958 1224 1679 1839 1993 37.0 50.2 62.8
1959 1116 1451 1284 1206 30.0 51.1 8.1
1960 1279 2003 1954 2160 56.6 52.6 68.9
1961 550 661 693 706 20.2 26.0 28.4
1962 2519 4130 4200 4326 64.0 66.7 71.7
1963 2289 3999 5199 4952 74.7 123.6 116.3
1964 1153 1324 1538 1235 14.8 33.4 7.1
1965 2223 4267 4950 4836 91.9 122.9 117.5
11 Yr. Av. 1418 2225 2419 2432 56.9 70.6 71.5

Plots Fertilized Every Other Year:
The hay yields from the plots fertilized in alternate years with ammonium nitrate are given in table 9. The alternate-year plots are fertilized in early spring at the same rates as the every-year plots. Fertilizer has been applied on these plots in 1957, 1959, 1961, 1963, and 1965. In general there has been some carry over-effect, from year to year, especially at the heavier rates. Carry-over from the dry season of 1961 to the comparably moist season of 1962 was especially marked, with practically no yield increases being obtained in 1961, but with very substantial increases being obtained in 1962, a year after the fertilizer applications were made.

As would be expected, the 1965 yields on the alternate-year plots were about equal to the 1965 yields on the every-year plots, and all rates of fertilization would have been profitable in that season. The 9-year average yields, however, show that 50 pounds of nitrogen every-other-year, does not produce quite as much forage as 25 pounds every year. Since the cost of application is less for the alternate-year, 50 pounds N treatment, it is apparent that either 25 pounds N every year or 50 pounds N every other year could be used profitably on crested wheatgrass stands in this area. There would be no economic justification for the use of the 100 pounds N every other year.

Table 9. Forage Production From Old Crested Wheatgrass Plots Fertilized Alternate Years1 at Three Rates of Nitrogen (33-0-0).
Year Check Dry Weight Yield - Lbs./Acre Percentage Increase Over Check
25 Lbs. N 50 Lbs. N 100 Lbs. N 25 Lbs. N 50 Lbs. N 100 Lbs. N
1957 1239 1714 2013 2001 38.3 62.5 61.5
1958 1003 1016 1114 1250 1.3 11.1 24.6
1959 1094 1230 1266 1659 12.4 15.7 51.6
1960 1306 1813 1801 2187 38.8 37.8 67.5
1961 554 608 658 624 9.7 18.8 12.6
1962 2298 3049 3265 3792 32.7 42.1 65.0
2963 2087 3106 3525 4829 48.8 68.9 131.4
1964 952 946 1101 1202 0.0 15.6 26.3
1965 2086 3919 4457 4823 87.9 113.7 131.2
9 Yr. Av. 1402 1933 2133 2485 37.9 52.1 77.2
1Fertilizer applied in spring of 1957, 1959, 1961, 1963, and 1965.

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