50 



If hay were valued at $25 per ton and nitrogen cost $0.13 per pound, more 

 nitrogen could be applied economically. Under these conditions, table 18 

 indicates that the maximum break -even range is 46 pounds of nitrogen for 

 0. 25 ton per acre increase. On curve "A, " under these conditions, the 

 range is as indicated by 2a (104 to 152 pounds of nitrogen): the midpoint is 

 128 pounds of nitrogen, and production per acre indicated is 1. 68 tons. On 

 curve "B, " the range is indicated by 2b, nitrogen is indicated at 97 pounds, 

 and production at 2. 58 tons per acre. 



It may seem strange that in the first instance (hay valued at $20. 00 per 

 ton and cost of nitrogen at $0. 15 per pound), the most profitable rate of 

 nitrogen application on curve "B" is greater than that on curve "A, " while 

 in the second case the reverse is true. This is due to the fact that curve 

 "A" has a more gentle slope - the meadow's response to nitrogen (nitrogen 

 efficiency) is greater at the higher rates of application than in the case of 

 curve "B. " At the lower rates of nitrogen application, the response to 

 nitrogen shown by curve "B" is greater, as indicated by the steeper slope 

 of the curve. The point here is that before the most profitable rate can be 

 approximated, a fairly good idea of the nitrogen response curve must be 

 obtained. 



This analysis indicates that there is precision in the answers, but in 

 reality there is no such precision. First, it is almost impossible to apply 

 exactly 71, or 171, pounds of nitrogen per acre. Second, even if the exact 

 response curve has been determined for a particular field by field trials 

 over a period of years, there is no assurance that weather, water, and so 

 on, during the current year will be the same as in the years during which 

 the trials were run. Despite these drawbacks, it is to the rancher's advan- 

 tage to determine the theoretical most profitable rate of nitrogen application 

 for his particular conditions. This gives him the maximum economic rate 

 of application, which is the real foundation of his eventual decision as to 

 "how much nitrigen to apply this year. " For this reason, the presentation 

 here has merit. 



WHY MIDPOINT IS MORE PROFITABLE THAN FULL APPLICATION RATE 



Table 18 indicates that, with 32 pounds of nitrogen per acre applied to a 

 meadow, production of hay must increase by 0. 25 ton per acre to allow one 

 break even, if hay is valued at $20 per ton and nitrogen costs $0. 15 per 

 pound. Applying this to curve "B, " figure 6, we find that if the rate of 

 application of nitrogen is increased from 60 to 92 pounds per acre, the 

 expected increase in production is 0. 25 ton per acre. When all costs are 

 considered, this last 0. 25 ton increase has just paid for itself and no more. 

 If this section of the curve is blown up and smoothed out, it shows that the 



