grain or row crops planted on the contour, 

 which was 0.7 percent of the total cropland in 

 the State (table 11). Contour farming occupied 

 2 percent of the land in Minnesota, 1.2 percent 

 in South Dakota, and 0.5 percent in Montana. 

 Among the States adjoining the Dakotas, those 

 leading in contour farming were Iowa with 

 8.8 percent, and Nebraska with 7.4 percent. 



The practice of stripcropping was much 

 more prevalent in North Dakota than contour 

 farming; 11.8 percent of the cropland was 

 stripcropped. In Montana, more than a third of 

 the cropland was stripcropped. In Minnesota, 

 2.6 percent was stripcropped; in Iowa, only 

 1.5 percent. 



Possible Limiting Factors 



There seems to be no apparent explana- 

 tion for the fact that terracing and contour 

 farming play an important part in the agricul- 

 ture of some neighboring States but not in 

 North Dakota. Level benches may prove to be 

 a more intensive land-use practice than ter- 

 races, but they offer some advantages not 

 found in either contour farming or conventional 

 terracing. Despite such advantages, it seems 

 prudent to speculate on some of the factors 

 which could limit or delay the adoption of 

 level benches. 



Climate 



Climate does not appear to be a limiting 

 factor in the adoption of level bench systems 

 in North Dakota because alfalfa will probably 

 respond to additional moisture supplies any- 

 where in the State. In North Dakota, where the 

 growing season ranges from 120 to 140 days, 

 irrigated alfalfa needs about 24 inches of 

 water annually (4). The probability of getting 

 more than 14 inches from precipitation in any 

 120-day period during the growing season is 

 less than 20 percent in all parts of the State 

 except the extreme southeastern corner, and 

 is less than 10 percent in all but the east- 

 central and south-central parts (19). This 

 leaves a water deficit of 10 inches or more in 

 the major portion of the State in all but 1 or 

 2 years in 10. It therefore follows that in at 



least 80 percent of the years of record, an 

 alfalfa crop probably would have given a meas- 

 urable response to additional water. 



Soil and Topography 



Soil and topographic conditions would limit 

 the use of level benches for crop production in 

 nearly every area of the State. Earlier it was 

 shown that benches 70 feet wide would be prof- 

 itable for alfalfa only on slopes of 5 percent 

 or less, and 56-foot benches on slopes of less 

 than 6 percent, and then only if the surface is 

 unusually smooth and even. On fields that are 

 nearly level, there would probably be no need 

 for benches. Thus, the most advantageous loca- 

 tion for level benches would be on fields with 

 smooth, even slopes between 1 and 6 percent. 



Soil texture would also limit the use of 

 benches. Coarse-textured soils, such as gravel 

 or sand, would not benefit because they lack 

 water-holding capacity. In some cases, fine- 

 textured soils, such as clays, might not be 

 suited to alfalfa production because they are 

 likely to be poorly drained, a problem which 

 might be aggravated rather than improved by 

 the construction of benches. 



The depth of the soil limits the amount 

 of cut and fill that can be made without seri- 

 ously reducing crop yields. On most soils, 

 the maximum cut should not go deeper than 

 the A horizon, so shallow soils might not be 

 suitable. 14- 



To clearly identify the areas that could 

 benefit from the use of benches, it would prob- 

 ably be necessary to use a land classification 

 system specifically designed for this purpose. 

 Such a system might be developed from the 

 data contained in a detailed soil survey, par- 

 ticularly if some supplementary data on top- 

 ography were available. Modern detailed soils 

 surveys are available for only a few coun- 

 ties in North Dakota. One good example is 

 Stark County, in the west-central part of the 

 State (15). From the data in the survey for 



14 A new experiment was started in 1969 to determine 

 the combined effects of a level bench system and deep 

 tillage on some solonetzic soils in western North Dakota. 



15 



