on a 1-percent slope without contributing areas 

 would produce 219 tons (table 6). The same 

 size benches on a 10-percent slope would 

 produce 187 tons. With contributing areas, 

 a field of 14-foot benches on a 1 -percent slope 

 would produce 181 tons of alfalfa, compared 

 with 167 tons on a 10-percent slope. A 100-acre 

 field on a natural slope with no benches would 

 produce 116 tons. 



The data in table 6 show that for any given 

 slope, the wider the bench, the higher the pro- 

 duction of alfalfa, because with wider benches 

 there are fewer dikes and therefore the area 

 available for harvest is greater. The yield per 

 acre on the harvested portion of each bench is 

 assumed to be the same regardless of its 

 width. This assumption may not be entirely 

 valid, because a field with narrow benches 

 would have more dikes with grass barriers to 

 trap snow. Thus, the narrow benches might 

 have higher yields per acre than the wide 

 ones. 



Where benches are built with contributing 

 areas, yield for the whole field is less than on 

 those without contributing areas. The yield 

 per acre is higher on benches with than without 

 a contributing area, but the natural slopes pro- 

 duce substantially less than either kind of 

 bench. If the ratio of contributing area to bench 

 is 1:1, then for every acre of bench there is 

 an acre of contributing area, and the effective 

 average yield for the whole field is substantially 

 reduced. 



Fixed Costs 



For amortizing the construction costs, 

 an average bench life of 30 years was arbi- 

 trarily selected, though a longer life seems 

 possible. To convert construction costs to 

 annual equivalents, the "capital recovery fac- 

 tor" method was used, with an assumed inter- 

 est rate of 7 percent. An annual charge of 

 $935 per 100 acres was assumed, to cover 

 the investment in land, machinery, and equip- 

 ment. 10 



10. 



The assumed charges for land and machinery and 

 the operating costs were developed from data presented 

 by Rice, Billy B„ and Paul, Rodney R,, Crop Costs and 

 Returns , N. Dak. Agr. Ext. Cir. FM-5-67, Fargo, 1967. 



To simplify the analysis, no allowance 

 was made for income losses connected with 

 the original construction of the benches. Under 

 normal circumstances, a full year of crop 

 production might be lost in building the benches 

 and establishing a stand of alfalfa. Even if the 

 benches were constructed in the fall after 

 harvest, it probably would not be possible to 

 get a stand of alfalfa ready for hay production 

 in the following year. 



Operating Costs 



Operating costs include costs for seed, 

 machinery, and labor for harvesting, including 

 the added costs associated with harvesting 

 small areas. An alfalfa stand will last for an 

 estimated 7 years at a seeding cost of $14 per 

 acre. This cost includes an allowance to com- 

 pensate for the reduction in income which 

 would probably occur during the year when the 

 stand is being reseeded. For purposes of esti- 

 mating harvesting cost, it was assumed that 

 cuttings would average 1 1/2 per year on 

 natural slopes. There would be 2 1/2 cuttings 

 per year on the benches because of increased 

 water supply. Harvesting costs other than labor 

 were assumed to be $7 per acre on benches 

 and $4 per acre on natural slopes. Labor was 

 valued at $1.50 per hour, resulting in a cost of 

 $10 per acre on the benches and $6 on natural 

 slopes. 



Adjustments were made for extra turning 

 and waste motion due to short fields and odd 

 areas. While the necessity for making such 

 adjustments is well recognized, it is difficult 

 to obtain specific data to serve as cost guide- 

 lines (20). It was assumed that the adjust- 

 ments would be in direct proportion to the 

 number of benches constructed on an aver- 

 age field of 100 acres, with benches built at 

 right angles to the longest (1/2 mile) side of 

 the field. 



The use of bromegrass or some other 

 permanent grass protects the dikes against 

 erosion, and from damage caused by harvest- 

 ing equipment. The benches and the dikes would 

 therefore be unusually stable, and there would 

 be little need for repair work once the stands 

 of alfalfa and bromegrass were established. 



10 



