2002-07-08_GENERAL DOCUMENTS - M2002004 (3)

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ably resulted from the improved soil phys- ical characteristics brought about by the . deep rooting of the barley - reflected by the infiltration data discussed later. We al- so attributed some of the increased produc- tion on the stubble plots to greater seedling establishment (6). Production of nonseeded species de- creased as topsoil depth increased on the stubble plots; however, little change oc- curred on the straw - mulched plots. Non- seeded species' production was significant- ly lower on the stubble plots than on the straw - mulched plots at the 400- and 600 -mm topsoil depths -the opposite of planted species' production. The greater nonseeded species' production on the straw - mulched plots probably resulted from the poorer grass establishment. This enabled weeds and other invading native species to become established in the open areas between the grass. Nonseeded species also competed with the seeded species for water and plant nutrients. Desirable, in- vading native species only accounted for a small percentage of the nonseeded species' production; however, these invading species would be important in overall plant community diversity. Many of the trends observed in the seed- ed species' production on the stubble - mulched plots were similar to the produc- tion of the barley used in establishing the stubble mulch. Barley production was 743, 878, 1,204, and 1,473 kg ha'' for the 0 -, 200 -, 400 -, and 600 -mm topsoil depths, re- spectively. Table 3 shows the effect of topsoil depth on the production of seeded and nonseeded species. Seeded species' production in- creased gradually over the 4 years with no topsoil, indicating a general improvement in spoil characteristics for plant growth. This trend, which would be expected as the vegetative community develops, was gen- erally true at all topsoil depths. However, it was not always statistically significant. Seeded species' production at the 400 - and 600 -mm topsoil depths was signifi- cantly higher in all 4 years. We attributed the greater production in 1981 and 1982 partially to greater precipitation than in the 2 previous years (Table 4). Nonseeded species' production varied within a given year, with greater produc- tion at the 0- and 200 -mm topsoil depths. Nonseeded species' production in 1981 was significantly greater than in all other years for all topsoil depths. This greater produc- tion occurred because of the above average precipitation in May (Table 4) and the be- low normal spring temperatures. Mulch type did not affect stored soil - water significantly; therefore, we aver- Table 2. Effect of mulch type on forage production by seeded and nonseeded species at the 0 -, 200-, 400-, and 800 -mm topsoil depths at a reclaimed mine site, Shirley Basin, Wyom- Ing, 1979-1982. Production by Mulching Method Crimped -Straw Mulch Stubble Mulch Topsoil Depth Seeded Nonseeded Seeded Nonseeded (mm) Species Species' Species Species kg ha - ' 0 328at 718a 431a 573a 200 435a 520a 393a 627a 400 697a 468b 898b 228a 600 666a 628b 950b 379a 'Nonseeded species production included Hordeum )ubatum, Salsola kali, Chenopodium album, Kochi scoparia, Sisymbrium altissimum, Poa spp. and Koeleria cristata. 'Each value represents 10 replications over 4 years, 1979 -1982; values within a topsoil depth and within seeded grass species or nonseeded species with the same letter are not significantly different at the 5% level as evaluated by Duncan's multiple range test. Table 3. Effect of topsoil depth on forage production by seeded and nonseeded species at a reclaimed mine site, Shirley Basin, Wyoming, 1979-1982. Topsoil Depth (mm) Seeded species 0 200 400 600 Nonseeded speciest 0 200 400 600 180aX• 372abX 445bX 671cX 448aX 243aX 323aX 408aXY Each value represents the mean of 20 observations; values within a year (within seeded or nonseeded species) with the same lower case letter and values across years within a top- soil depth with the same capital letter are not significantly different at the 5% level as evaluated by Duncan's multiple range test. tNonseeded species included Hordeum jubatum, Salsola kali, Chenopodium album, Kochia scoparia, Sisymbrium altissimum, Poa spp. and Koeleria cristata. Table 4. Monthly precipitation during the growing season and annual precipitation, Shirley Basin, Wyoming, 1977 -1982. Year March April May June July August Annual 1977 40 37 35 5 24 8 208 1978 13 42 69 20 24 29 266 1979 18 9 14 12 20 20 157 1980 10 4 54 2 18 30 167 1981 18 12 92 4 51 13 243 1982 1 10 39 51 70 21 257 aged data across mulch treatments (Table 5). Spring soil water levels were inversely proportional to topsoil depth. This phe- nomena occurred because the water -hold- ing capacity of the topsoil was less than that of the spoil placed below the topsoil (5). Subsoil material had about one -third greater water - holding capacity than the topsoil at 1/3 -bar matric potential. Schu- man and Taylor (5) also reported that sub- soil material contained about 44% more water at 15 -bar matric potential than did topsoil. The data clearly show the differ- ence in water - holding capacity between topsoil and spoil (Table 5, below line, spoil; above line, topsoil) . Deep ripping resulted in some mixing of 1979 1980 1981 274aXY 356aX 689bY 756bX 689bY 370aXY 245aX 189aX Production by Year kg ha - ' Precipitation (mm) 410aY 446aX 968bZ 984bY 1,115bZ 1,133bZ 605aY 952bZ 1982 656aZ 483aX 1,091 bZ 823bX 332abX 549bY 222aX 467abY Table 5. Effect of topsoil depth on storage and profile distribution of soil water, aver- age values obtained In March of 1978 through 1982. Stored Water by Topsoil Depth (mm) Profile Depth (mm) 0 200 400 600 0 -150 33.5b* ( 30.0a 29.2a 27.2a 150 -300 40.6b 38.4b 26.7a 25.7a 300 -600 89.4b 85.3b 80.3b 156.9a 600 -900 91.8a 86.1a 89.4a 85.3a Total 255.3 239.8 225.6 195.6 *Each value represents the mean of 50 ob- servations taken over 5 years; values fol- lowed by the same letter within a profile sampling depth increment are not signifi- cantly different at the 5% level as evalu- ated by Duncan's multiple range test. March -April 1985 251