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INFLUENCE OF NITROGEN ON OLD CRESTED WHEATGRASS STANDS

The nitrogen fertilizer trial on old crested wheat grass stands, begun in 1951, was concluded this year with the clipping of the plots which were fertilized in the spring of 1954. In this trial a new area was fertilized each year and the residual effects of the initial fertilization were determined by clipping each year following the application until no visible response could be detected. A new trial was begun this year in which the same plots will receive the same amount fertilizer each year. The 50 and 100 lb. rates of N application have been retained in the new study, and a lighter rate, 25 lbs. N, has been added. The heavy rate, 150 lbs. N, has been discontinued.

Table 8 gives the results of the five year study of the influence of nitrogen fertilizer on the production of crested wheat grass hay from old stands. Rates of application in this trial have been light, 195 lbs. of fertilizer per acre (50# N); medium, 300 lbs. of fertilizer per acre (100# N); and heavy, 450 lbs. of fertilizer per acre (150# N). The fertilizer has been applied in the spring by broadcasting on the surface from the fertilizer attachment of a grain drill.

The data from the trial as summarized in Table 8 show that substantial percentage increases in yield have been obtained from all rates of application.

Table 8. Influence of Nitrogen Fertilizer Treatments on Forage Production from an old Crested Wheat grass Field. Hay Yields in Pounds per Acre, Over-dry .
Time of Application Year of Yield Yields from Treatments Percentage Increase in Forage Production Total Additional Forage Production
No N Check 50# N Light 100# N Medium 150# N Heavy Light Medium Heavy Light Medium Heavy
Spring - 1951 1951 1627 1976 2233 2250 21.5 37.2 38.2 349 596 623
1952 467 456 720 841 5.4 54.2 80.1 25 253 374
1953 3330 3532 4481 4485 6.1 64.6 34.7 202 1151 1155

Total for 3 years

576 2000 2152
Spring - 1952 1952 366 609 636 716 69.1 73.8 95.6 253 270 350
1953 2897 4507 4635 5596 55.8 60.0 93.1 1610 1738 2695

Total for 2 years

1863 2008 3045
Spring - 1953 1953 2761 4348 5508 5354 57.5 99.5 93.9 1587 2747 2593
Spring - 1954 1954 1243 1953 2083 2381 57.1 67.6 91.6 710 840 1138
1955 1124 1227 1404 1782 9.2 24.9 58.5 103 280 658

Total for 2 years

813 1120 1796

The medium and heavy rates have increased the yield more than the light rate, but these increases in yield have not generally been proportional to the additional amounts of nitrogen supplied. The average increase in production from a light application of nitrogen has been 1201 lbs. per acre; from a medium application 1969 lbs.; and from a heavy application 2441 lbs. Thus the first 50 lbs. of nitrogen has produced 1201 lbs. of dry hay; the second 50 lbs. increment has produced an additional 768 lbs. of hay; and the third 50 lb. increment of nitrogen has produced only 472 lbs. of additional hay. The first 1200 lbs. of additional hay requires only 50 lbs. of nitrogen, but to get another 1200 lbs. of hay, 100 more pounds of nitrogen are required. The results thus far would seem to indicate that it would be difficult to justify the use of nitrogen at rates greater than 50 lbs. per acre in this area.

The first year results from the new fertilizer trial are given in Table 9. Twenty five pounds of nitrogen gave the surprisingly good increase in yield of 820 lbs. per acre of dry hay. Fifty pounds of nitrogen gave only slightly better yields, but 100 pounds of nitrogen produced 1214 lbs. per acre of extra hay. The present results will become of significance primarily when the effects of repeated applications of nitrogen to the same plots begin to show.

Table 9. First Year Yields From the Application of Nitrogen Fertilizer to old Stands of Crested Wheat grass.
Yield Factors Rate of Application lbs. per acre
Check No N Very light 25# N Light 50# N Medium 100# N
Yield - lbs. per acre 1276 2096 2121 2494
Increase over check --- 820 845 1218
Percentage increase --- 64.3 66.2 95.4

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