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FERTILIZER ON NATIVE GRASS

The trial with nitrogen fertilizer on native grass on four different range sites was continued for the second season in 1965. Plots on each of the sites were fertilized at 33, 67, and 100 pounds N per acre. The sites are designated by the name of the soil type on which they are situated. The sites included Flasher (sandy hills), Havre (sagebrush flat), Solonetz (panspot alkaline soil), and Farland (high terrace). The Flasher site is at the Dickinson Station, the Havre site is at Pyramid Park, the Solonetz site is on the Nick Oe ranch south of Belfield, and the Farland site is on the Bobb ranch south of Taylor.

The fertilizer applications were made in the spring of 1965, as they were in the spring of 1964. Portions of the vegetation on each plot were protected by steel cages, and the vegetation under the cages was clipped at the end of the growing period to provide and estimate of total yield. Yield data from each of the sites are given in Table 12. The yields on the sites from all plots, both control and fertilized, were appreciably better in the 1965 season than in the 1964 season. In terms of total increase in yield over the control plots the Flasher site was the most responsive to the fertilizer treatments, the Farland second, Havre third, and the Solonetz last.

The comparison of total yields of grass is probably more significant than the comparison of total yields of vegetation from the sites. On the Flasher site the first 33 pounds of nitrogen produced 308 pounds of grass more than the check plots. This increment of nitrogen produced 289 pounds additional grass on the Havre site, 228 pounds additional on the Solonetz site, and on the Farland site there was actually slightly less grass produced on the 33 pounds N plots than on the check plots. The 67 pounds N treatment increased grass yield on the Flasher site by 1067 pounds per acre, on the Havre site by 1162 pounds, on the Solonetz site 489 pounds, and on the Farland site by 872 pounds per acre. At the 100 pound rate the production of grass on the Flasher site was 1449 pounds more than on the check, 1478 pounds more on the Havre, 595 pounds more on the Solonetz, and 383 pounds more on the Farland.

Despite the relatively higher overall production in the 1965 season than in the 1964 season, none of the rates of fertilizer application doubled the production of grass on any of the sites. The 33 pound rate, in terms of grass production alone, was not economical on any of the sites. The 67 pound rate was economical on the Flasher, Havre, and Farland sites; and 100 pound rate was economical only on the Flasher and Havre sites. None of the rate were economical on the Solonetz site figuring nitrogen at .10 per pound and valuing grass at .01 per pound. It should be pointed out the vegetation on all these sites would normally be harvested by grazing animals, and the returns from grazing might require a considerably different type of evaluation from that afforded by clipping yields.

Probably the forb yields should not be disregarded, since at least a portion of the forb production is suitable as livestock forage. However, most of the forb yield on all sites represents low value forage. Forb production was greatly stimulated on the Farland site by the fertilizer applications, with over half the total yield of 3504 pounds on the 100-pound-N treatment being perennial forbs. Stimulation of forb production by the fertilizer was also substantial on the Flasher site. The need for the use of herbicides on some sites in order to get maximum benefits from the fertilizer applications is apparent from these results.

Table 13 gives the percentage composition of the yields from the sites in the 1965 season as divided into three categories, (1) mid and tall grasses; (2) short grasses; (3) forbs. This analysis provides the basis for comparing the composition of the yields of fertilized vegetation with the composition of the check yields to determine whether all components of the vegetation were stimulated to approximately the same degree or whether some were stimulated more than others. From the data given in table 13 it would appear that the mid and tall grass component of the vegetation on the Flasher site was stimulated more than the other components under the 100-pounds-N treatment. On the Havre site it is apparent that the mid and tall grass component also showed greater stimulation than the other components of the vegetation at all three levels of fertilizer application. There apparently was very little differential stimulus on the Solonetz site at any of the fertilizer levels. The forb component of the vegetation was greatly stimulated on the Farland site by all levels of fertilizer application.

Table 14 gives the average yields on the sites for the two years of the trial, 1964-1965. On the basis of the grass yields the Havre site has been the most responsive of the sites, followed by the Flasher and the Farland. The Solonetz site has been the least responsive in terms of total extra grass. The 67-pound rate of application appears to be the most economical in terms of relative fertilizer costs in relation to pounds of grass produced. The 33-pound rate has been near the break-even point on the Havre and Flasher, but well below this point on the Farland and Solonetz. The dat indicate clearly that initial Commercial work with fertilizer applications should largely be confined to the sites most likely to give a profitable response.

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