2002-07-08_GENERAL DOCUMENTS - M2002004 (4)

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10am In texture, and the underlying spoil was silt loam. Identical plot areas were laid out at each of the six sites. Each plot was split with corn seeded on one half and small grain (barley in 1980 and 1981, wheat in 1982) on the other half. Corn and small grain were rotated between subplots each year so that in 1981 and 1982, small grain was grown following corn and corn was grown following small grain. At both locations, reclamation of the reclaimed sites was completed in the spring of 1980 just prior to establishment of the experimental plots. In 1980, small grain yields were not obtained because of poor stands and poor growth from the reclaimed sites at both Beulah and Center. Corn silage yields at both sites were lower on the reclaimed sites than on the undisturbed sites (Table 19). In 1981 and 1982 , yields from the reclaimed sites tended to approach or equal those from the undisturbed sites. Similar yield trends have been noted when newly reclaimed soils were cropped in other experiments. Until the soil structure and moisture levels become reestablished in disturbed soils, optimum crop yields cannot be ex- pected. At these two sites, the yields from reclaimed soils in the last two years generally tended to ap- proach or equal those from undisturbed soils. It should be noted that soil and spoil materials at both locations were medium to fine in texture. Table 19. Yields of small grains and corn on undisturbed and reclaimed soils at the Knife River Mine at Beulah and the Baukol•Noonan Mine at Center. Year Mine Soil 1980 1981 1982 Small grains' bushels /acre Beulah Undisturbed Prime 1.4 12.5 33.2 Nonprime 19.8 22.4 34.1 Reclaimed 18.4 21.1 Center Undisturbed Prime 21.4 39.9 31.0 Nonprime 4.1 28.6 19.7 Reclaimed 2 19.3 29.6 Com Silage tons /acre Beulah Undisturbed Prime 1.7 6.0 9.0 Nonprime' 2.7 7.2 8.2 Reclaimed 1.1 10.8 7.2 Center Undisturbed Prime 12.7 10.4 10.2 Nonprime 7.5 7.1 9.6 Reclaimed 6.2 9.3 9.4 'Barley in 1980 -81, wheat in 1982 'Not harvested due to drought and /or poor stand 'Fallowed in 1979, all other undisturbed sites at both locations were cropped in 1979 15 DISCUSSION The depth of soil materials that must be replaced to restore soil productivity is dependent upon the chemical and physical properties of the underlying spoil. In turn, the potential productive capacity (or productivity index) of reclaimed soil is related to the chemical and physical properties of the root zone, which may include not only replaced soil materials but also the uppermost portion of the reshaped spoil. The productivity index at any specific site is also dependent upon topographic position. Further- more, the yields given herein for the various ex- periments are a reflection not only of the productivi- ty index, but also of seasonal climatic conditions, of soil and crop management practices, and of disease and insect infestations. While the cumulative effect of all these factors may initially appear to com- plicate evaluation of the results, the authors feel that adequate data are available to substantiate the for- mulation of general site - specific guidelines. When adequate amounts of suitable soil and spoil materials are available, soils can be reclaimed to pro- ductive levels which frequently exceed the premine capacity. But suitable materials are not always available, either in quantity or quality, for optimum productivity. The materials that are available must then be properly utilized for restoration to the best possible postmine use. To do this, the properties and characteristics that govern the productive capacity of soils must be known, and the processes that affect changes in soil characteristics must be understood. Fortunately, much of this information is available in published reports of soils research. The results of this research need to be adapted to define the desirable properties and characteristics for op- timum productivity for use as a guide (or standard) for planning the reclamation of stripmine soils. Characteristics of productive North Dakota soils: Undisturbed soils are continually changing in response to environmental factors, but over a long period of time have reached a "steady state" in which these changes are extremely slow. These en- vironmental factors have been described by Jenny (1941) as 1) climate, 2) living organisms, 3) parent material, 4) topography and 5) time. Climate is the only one of these factors that is not affected to some degree during reclamation. When soils are drastical- ly disturbed by stripmining, this "steady state" is disrupted, and reclaimed soils immediately begin to change in response to these environmental factors. The objective of reclamation is to restore soils as nearly as possible to a "steady state" and to ensure that subsequent changes in response to the above soil- forming factors will result in increased produc- tivity. Research in North Dakota has shown that the two most important soil properties that can be modified by changes in the soil environment during reclamation are 1) water infiltration and retention