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

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40 A. 1). Day, T. C. Tucker and J. L. Thames evaporation and by reducing air movement and solar energy at the soil -air interface (Adams et al., 1976). Lal (1974) noticed a temperature difference of 8 °C between mulched and un- mulched tropical soils. Mulching reduced soil - temperature down to the 20 -cm depth. Allmaras and Nelson (1971) reported that straw mulch strips reduced soil - temperature and metric suc- tion to the 45 cm soil depth, while black plastic mulch had no effect on soil- temperature below the 15 cm depth. Bansal et al. (1971) observed that soil- moisture and soil - temperature were higher under polyethylene mulch than they were under straw mulch. The addition of large quan- tities of plant residues to soil materials reduced soil- temperature and soil - moisture Toss from evaporation (Greb et al., 1970). Osbore and Gil- bert (1978) stabilized a highway slope with vege- tation by mulching the surface with shredded hardwood bark to reduce erosion and runoff. Lattanzi et al. (1974) stated that runoff from rain- fall can be reduced by the addition of sufficient soil mulch to protect the soil from surface sealing by raindrop impact. Michael and Blackard (1978) found that the application of high rates of soil mulch significantly reduced runoff volume and maintained a high moisture infiltration rate. The purpose of this study was to compare Russian thistle (Salsola Tali L.) mulch with bar- ley (Hordeunr vulgare L.) straw mulch in reduc- ing soil - moisture loss from coal mine soil mate- rials. MATERIALS AND METHODS Greenhouse experiments were conducted in 1978 in Tucson, Arizona to compare Russian thistle mulch with barley straw mulch in reducing soil- moisture loss from coal mine soil materials obtained from the Black Mesa Coal Mine, near Kayenta, Arizona. Three soil materials were studied in these ex- periments: (a) coal mine soil (a miscellaneous land type), (b) unmined soil (Fniitland soil series) that belongs to the soil family of coarse -loamy mixed (calcareous). mesic Typic 'I'oriorthents, and (c) Red Mesa loam soil —a member of the Haplargid great group. Each soil material was observed without mulch, mulched with Russian thistle, and mulched with barley straw to make a total of nine soil treatments. The mulched soil materials were prepared by mixing the soil and the mulches (coarsely ground) in the ratio of two parts of soil material to one part of mulch, on volume basis. The nine soil materials were ar- ranged in a Randomized Complete Block design with four replications. The experimental units were 7 cm diameter waxed paper cups. Prior to the studies, the soil materials were allowed to stand in the greenhouse for seven days to attain a uniform moisture content in equilibrium with the greenhouse environment, which was maintained with thermostatically - controlled heaters and evaporative coolers. A hygrothermograph was used to monitor the greenhouse temperature and relative humidity. After the seven -day period, 50 ml of tap water was added to each cup and the total weight was recorded to the nearest 0.1 g. Weights were recorded daily for six days to de- termine the percent moisture loss from each soil material. The studies involved two experiments re- peated three tines in each of two environments. Environment 1 was a temperature of 27 °C and 54% relative humidity and Environment II was a temperature of 21 °C and 75% relative humidity. Moisture loss was calculated as a percentage of the initial 50 ml of water added to the soil materials. All data were analyzed using the standard analysis of variance and means were compared using the Student - Newman- Keuls' Test as de- scribed by Little and Hills (1972). RESULTS AND DISCUSSION The average soil - moisture loss for nine soil materials in two greenhouse environments is shown in Table 1. Barley straw and Russian this- tle mulches significantly reduced soil- moisture loss from Red Mesa loam soil, unmined soil, and coal mine soil material. In Environment I (27 °C and 547 relative humidity) the three soil materials without mulch lost about 80/0 of their original soil - moisture con- tent and about 75% of their original moisture con- tent when they were mulched with barley straw or Russian thistle. Soil- moisture loss from all the soil materials was lower in Environment 11 (21 °C and 75i4 rela- tive humidity) than it was in Environment 1: how- ever, the two environments followed the same pattern of soil - moisture Toss. In Environment 11, soil- moisture loss from Red Mesa loam soil with- out mulch was significantly lower than it was from unmined soil and coal mine soil material without mulch. The addition of barley straw and Russian thistle mulches to each of the three soil materials in Environment II reduced their soil moisture loss by the same amount. The data reported in this paper indicated that the decrease in soil - moisture loss from coal mine 1 r :r c u t1 t: ti