The development of nitrates in soil with sweetclover residues on the surface and cultivated by subsurface tillage was compared with nitrate production under conventional tillage where the sweet-clover residues were plowed under. The investigation was conducted on field plots at Lincoln, Neb., in first- and second-year corn after first- and second-year sweetclover over a 6-year period, and in wheat. Sampling for nitrates was done to a depth of 6 feet. The available nitrogen in the subtilled plots with first-year corn after first-year sweetclover was lower than on the plowed plots in 4 years out of 6. To a depth of 6 feet the mean available nitrogen for the 6-year period of the subtilled plots was about 7% lower than with the plowed plots. Also, on plots with second-year corn after first-year sweetclover, the available nitrogen to a depth of 6 feet was about 7% lower on the subtilled plots. The mean available nitrogen for a 5-year period in first-year corn after 2 years of sweetclover to a depth of 6 feet was 10% lower on subtilled plots than on plowed plots. In second-year corn after 2 years of sweetclover the mean available nitrogen to a depth of 6 feet for 3 years was about 8% lower on the subtillage than on the plowed plots. Nitrate determinations in 3 different years in corn land made about the first of November, after the corn was mature, showed a higher available nitrogen content on the subtillage than on the plowed land. Some of this seems to have carried over into the next season. This was shown by the fact that the increase in nitrate on the plowed land over subtilled was less in the second-year corn than in the first-year. In the seedbed for winter wheat in 3 different years the mean available nitrogen to a depth of 6 feet was slightly lower on the subtilled than on the plowed areas. The amounts of available nitrogen produced were large in every test and potentially sufficient to produce large yields of corn or other crops. That the nitrification process following the growing of sweetclover was slower under the subsurface tillage system than under the plowing system is to be regarded as a desirable circumstance in a region of limited rainfall. On the other hand, the high nitrate levels that were obtained under subsurface tillage through the growing of sweetclover are also desirable in areas of depleted soil where a residue cover is important for erosion control.

Cheatgrass, an aggressive winter annual native to southern Europe, appeared in Idaho before 1900. It is well adapted to climatic conditions in southern Idaho and invades on ranges wherever native vegetation has been disturbed. Undisturbed cheatgrass stands average about 570 plants per square foot. Current studies indicate that if this number can be reduced to 50 plants per square foot (80 plants per square foot if reduction is by burning and 100 if by lister drill) for one season, perennial grass seedlings can become established and occupy the area. The best season for reducing the number of cheatgrass plants through cultural treatments is in the spring before seed forms; the next best, after fall germination. The most effective but a costly method of eliminating cheatgrass and getting good stands of reseeded grass is moldboard plowing at any season of the year followed by fall drilling. A good alternative is wheat land plowing or heavy disking in spring, or in late fall if cheatgrass has germinated vigorously, followed by fall drilling. Early summer burning, usually in June, followed by fall drilling is a cheap method and data in four consecutive years indicate that good results may be expected. Deep-furrow lister drilling in late fall gives good results when cheatgrass has germinated. Crested wheatgrass is the most universally recommended species for seeding on cheatgrass areas and should form the major part of all reseeding mixtures for southern Idaho. Bulbous bluegrass is well suited for poor sites and as an understory species on some areas of southwestern Idaho. Other species which may be used on the drier cheatgrass areas are bearded bluebunch, beardless bluebunch, stiffhair, and intermediate wheatgrasses. Species for the better and moister sites are smooth and mountain brome, tall oatgrass, intermediate and tall wheatgrass, Russian wildrye, and big bluegrass. Seeds should be drilled wherever possible. Drill furrows are best spaced from 6 to 8 inches apart with seed covered from 1/2 to 3/4 inch deep. Wherever feasible, drill furrows should be cut to 1 1/2 inches or more deep, with very light covering of soil on the seed in the bottom of the drill furrow. Where fall moisture is dependable, seedings in cheatgrass areas may be done in September or early October. Where fall moisture is not dependable, seeding should be delayed until late October or early November.