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dues left on the surface, corn could be
<br />gown on Maury soil with a slope up to
<br />20% and still be within the tolerance limit
<br />of 9 Mg ha -' yr -', according to USLE cal-
<br />culations (11).
<br />Conclusions
<br />?Farmers increasingly are growing row
<br />crops on sloping land and using conven-
<br />tional tillage practices on formerly idle
<br />land or grassland to help maintain their in-
<br />come. Although no -till and other forms of
<br />conservation tillage are becoming more
<br />popular, soil erosion remains an important
<br />problem.
<br />Our study suggests that farmers can con-
<br />tinue to produce corn on sloping land
<br />while maintaining or increasing yield, in-
<br />come, and soil productivity over time by
<br />using no-till and an adapted legume cover
<br />crop as a partial source of N in combina-
<br />tion with chemical N fertilizers.
<br />REFERENCES CITED
<br />1. Blevins, R. L., C. W. Thomas, M. S.
<br />Smith, W. W. Frye, and P. L. Cornelius.
<br />1983. Changes in soil properties after 10
<br />years of continuous non - tilled and conven-
<br />tionally tilled corn. Soil and Tillage Res. 3:
<br />135 -146.
<br />2. Browning, W. C. L. Moore, Sr., K. Ander-
<br />son, and D. L. Debertin. 1982. Estimated
<br />costs and returns for production of various
<br />crops and livestock in Kentucky during
<br />1982. Agr. Econ. -Ext. No. 16. Dept. Agr.
<br />Econ., Univ. Ky., Lexington.
<br />3. Ebelhar, S. A., W. W. Frye, and R. L.
<br />Blevins. 1984. Nitrogen from legume cover
<br />crops for no-tillage corn. Agron. J. 76:
<br />51 -55.
<br />4. Frye, W. W., J. H. Herbek, and R. L.
<br />Blevins. 1983. Legume cover crops in
<br />production of no- tillage corn. In W. Lock -
<br />eretz [ed.] Environmentally Sound Agri-
<br />culture. Praeger Publishers, New York,
<br />N.Y.
<br />5. Frye, W. W., R. L. Blevins, L. W. Mur-
<br />dock, and K. L. Wells. 1981. Energy con-
<br />servation in no- tillage production of corn.
<br />In Crop Production with Conservation in
<br />the 80's. Publ. 7 -81. Am. Soc. Agr. Eng.,
<br />St. Joseph, Mich.
<br />6. Phillips, R. E., R. L. Blevins, G. W.
<br />Thomas, W. W. Frye, and S. H. Philips.
<br />1980. No-tillage agriculture. Science 208:
<br />1,108 - 1,113.
<br />7. Thomas, G. W., and W. W. Frye. 1984.
<br />Fertilization and liming. In R. E. Phil-
<br />lips and S. H. Phillips [eds] No-Tillage
<br />Agriculture: Principles and Practices.
<br />Van Nostrand Reinhold Co., New York,
<br />N.Y.
<br />8. U.S. Department of Agriculture 1982.
<br />Handbook of agricultural charts. AH No.
<br />609. Washington, D.C.
<br />9. U.S. Department of Agriculture, Soil Con-
<br />servation Service. 1978. Predicting soil loss
<br />using the universal soil loss equation. Lex-
<br />ington, Ky.
<br />1 Utomo, M. 1983. Effects of legume cover
<br />crops on soil nitrogen, soil temperature and
<br />soil moisture in no- tillage corn. M.S. thesis.
<br />Univ. Ky., Lexington.
<br />1. Wischmeier, W. H., and D. D. Smith.
<br />1978. Predicting rainfall erosion losses, a
<br />guide to conservation planning. Agr. Hand -
<br />bk. No. 537. U.S. Dept. of Agr., Washing-
<br />ton, D.C.
<br />nwvegeiativn OT minea Tana:
<br />Influence of topsoil depth
<br />and mulching method
<br />G. E. Schuman, E. M. Taylor, Jr., F. Rauzi, and B. A. Pinchak
<br />ABSTRACT: Land disturbance from more extensive surface mining in the Northern
<br />Great Plains poses the question of how much topsoil (A and B horizon) material is neces-
<br />sary to restore these sites. The effect of topsoil depth and mulching method on the forage
<br />production of seeded species was investigated on reclaimed uranium lands in Wyoming
<br />between 1977 and 1982. Water infiltration and storage were also tested. In the fall of
<br />1977, on plots with topsoil depths of 0, 200, 400, and 600 mm, a mixture of three wheat -
<br />grass species and green needlegrass was seeded directly into barley stubble and fallow
<br />plots mulched with 5 t/ha -' of barley straw. Forage production by these seeded species
<br />from 1979 through 1982 generally was greater on plots with 400 or 600 mm topsoil that
<br />had been established with stubble mulch, compared to those with straw mulch. With 400
<br />and 600 mm of topsoil, infiltration increased from 1979 to 1982, suggesting that the soil
<br />physical characteristics improved because of plant root penetration into the soil. Stubble -
<br />mulched plots exhibited significantly greater infiltration than straw- mulched plots at the
<br />600-mm topsoil depth in all years.
<br />N EARLY half of the nation's strippable
<br />coal reserves underlie agricultural
<br />land in the Northern Great Plains. Extrac-
<br />tion of uranium, bentonite, and other
<br />mineral resources also results in major land
<br />disturbance. Most of this land is range-
<br />land, used for forage production for graz-
<br />ing livestock and wildlife. Most state laws
<br />require reclamation of such lands to a pro-
<br />ductivity level equal to or greater than that
<br />prior to mining. Federal and state laws
<br />also require that soil resources be removed
<br />before mining and redistributed over the
<br />reconstructed landscape.
<br />But how much topsoil is necessary to re-
<br />claim these areas to their original level of
<br />productivity? Studies in North Dakota,
<br />Wyoming, and Colorado have provided
<br />varying answers, depending on soil and
<br />spoil characteristics. A study of the effect
<br />of topsoil and subsoil thickness on produc-
<br />tivity above sodic spoil showed that in most
<br />instances over 90% of maximum forage
<br />yields were obtained when at least 900 mm
<br />of soil were placed over the spoil (4). With
<br />no topsoil, only native blue grama and
<br />sideoats grams produced over 75% of
<br />maximum observed forage production on
<br />G. E. Schuman and E. M. Taylor are soil sci-
<br />entists with the Agricultural Research Service,
<br />U.S. Department of Agriculture, Cheyenne,
<br />Wyoming 82009; F. Rauzi, now retired, was a
<br />soil scientist with ARS -USDA, Laramie, Wyom-
<br />ing, and B. A. Pinchak is a graduate research as-
<br />sistant, University of Wyoming, Laramie. This
<br />article is a contribution from the High Plains
<br />Grasslands Research Station, ARS -USDA,
<br />Cheyenne, Wyoming 82009, in cooperation
<br />with the Wyoming Agriculturl Experiment Sta-
<br />tion. Laramie, and Pathfinder Mines Corp.,
<br />Shirley Basin Mine, Shirley Basin, Wyoming.
<br />undisturbed rangeland. That study also
<br />found that topsoil thickness did not influ-
<br />ence water extraction by vegetation.
<br />McGinnies and Nicholas (3) reported that
<br />460 mm of topsoil placed over spoils in Co-
<br />lorado improved stand establishment and
<br />plant growth.
<br />Barth and Martin (1) conducted re-
<br />search on topsoil depth at 15 locations
<br />throughout the Northern Great Plains.
<br />They found that the topsoil depth neces-
<br />sary for maximum forage production
<br />ranged from 0 to 1,520 mm, depending up-
<br />on spoil characteristics. They found that
<br />(a) 500 mm of topsoil was optimum for
<br />nonsaline, nonsodic spoils with a neutral
<br />pH, (b) that 830 mm of topsoil was opti-
<br />mum for sodic spoils having alkaline reac-
<br />tion and high clay content, and (c) that
<br />1,520 mm of topsoil was necessary for acid-
<br />ic spoils. They found no effect of topsoil
<br />depth on fora a roduction when topsoil
<br />and spoil had similar characteristics.
<br />Topsoil depth and spoil quality can
<br />greatly influence productivity and longev-
<br />ity of the vegetation established on re-
<br />claimed lands.
<br />Our study sought to determine the ef-
<br />fects of topsoil depth and mulching method
<br />on the productivity of reestablished,
<br />native, seeded forage species, the produc-
<br />tivity of nonseeded species, and water in-
<br />filtration and storage. We define topsoil as
<br />A and B soil horizon material.
<br />Methods and materials
<br />Field plots, established in the spring of
<br />1977, were at the Pathfinder Mines' open -
<br />pit uranium mine, the Shirley Basin Mine,
<br />March - April 1985 249
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