THE ECONOMICS OF FERTILIZING BROMEGRASS IN SASKATCHEWAN

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Abstract
A 5-yr study on a Dark Brown Loam at Scott and a 9-yr study on a Gray Luvisolic loam at Loon Lake, Saskatchewan, were used to determine the effect of rate of urea (46-0-0) and ammonium nitrate (34-0-0) fertilization on net returns from bromegrass (Bromus inermis Leyss.) production when the N was broadcast annually or as a single application at the start of the experiment. Each N source was applied at annual rates of 0, 50, 100, and 200 kg N ha−1 and at single application rates of 0, 100, 200, 400, and 800 kg ha−1. The ammonium nitrate was also applied at rates of 600 and 1000 kg ha−1. Comparisons of the discounted present value of net returns (NPV) over the study periods showed that N fertilization was highly profitable for all treatments under most forage price, N cost, and interest rate situations. The application of ammonium nitrate was consistently more profitable than urea despite its higher unit cost. At Scott, the 5-yr economic advantage of ammonium nitrate over urea averaged $53–$117 ha−1 for annual applications and $34–$72 ha−1 for single applications when forage price was varied from $0.05 to $0.09 kg−1; at Loon Lake, the corresponding 9-yr advantage of ammonium nitrate averaged $48–$121 ha−1 for annual and $25–$59 ha−1 for single applications. When price was adjusted to reflect forage N and P composition, the economic advantage of using ammonium nitrate over urea was enhanced. For treatments receiving similar rates of total applied N by both methods of application, NPV was generally higher when the N was applied in smaller doses annually compared to all at one time. At Scott, this effect was consistent at all N rates and for both N sources, but at Loon Lake, where moisture was more favorable, single applications at lower N rates often provided similar NPV as for annual N applications. The most profitable fertilizer treatments at Scott and Loon Lake were the 100- and 200-kg ha−1 rates of ammonium nitrate-N applied annually. When forage yields were related to N rate, moisture, and stand age for the annual N application treatments the economic optimum N rates depended greatly on the expectations for moisture, level of risk aversion, and on the ratio of fertilizer N cost to forage price. The optimum application rates of ammonium nitrate-N averaged 7–14 kg ha−1 higher at Scott and 8–27 kg N ha−1 higher at Loon Lake compared to those for urea. Further, the optimum N rates were higher than the general recommendation for bromegrass grown in these regions; thus producers should consider using higher N rates than has been the tradition for maximum economic return.Key words: Net returns, bromegrass hay, N source, N rates, application method