PERSISTENCE, BIOMASS YIELD AND SPREAD OF TEN GRASSES ON A DISTURBED SITE IN CENTRAL TEXAS

Paul E. Boldt, Charles R. Tischler, Bruce A. Young, and Ralph A. Hicks

Research Entomologist, Plant Physiologist, and Research Geneticist,

USDA­ARS, Temple,TX, and Research Associate, Blackland

Research Center, TAES, Temple, TX, respectively

Abstract

Ten grass species were established from transplants on a site in Central Texas which had been stripped of topsoil and was low in organic matter, nitrogen, and phosphorous. Switchgrass performed best on the site, followed by sideoats grama, indiangrass, and big and little bluestem. Buffalograss persisted but was masked by competing vegetation. Kleingrass, blue grama, Cochise lovegrass, and green sprangletop did not persist.

Introduction

During the 1950's, a large earthen dam, Belton Dam, was built on the Leon River near Belton, Texas by the Army Corps of Engineers. This dam was constructed with 10 to 20 feet of surface soil, removed from a 50 acre area immediately downstream from the dam site. In 1991, additional soil was removed from the same area for construction of a nearby road. The following year, Lake Belton, formed by the dam, overflowed and the area was flooded for several months. This resulted in extensive erosion of the already depleted soil. As a result, this area presently supports sparse vegetation consisting mainly of King Ranch Bluestem (Bothriochloa ischaemum), various annual threeawns (Aristida sp.), and legumes such as Golden Dalea (Dalea aurea), Purple Prairie Clover (Petalostemum oulcherrimum) and partridge pea (Cassia fasciculata). Ground cover is probably less than 30 percent.

In 1993, a group of interested citizens formed the Miller Springs Nature Alliance to develop the eroded area and the adjacent 200 acres to be used as an educational center and a site for the study of ecological issues. One of the goals of the Alliance is to increase the productivity of the eroded area by planting grasses and other plants to reduce erosion, rebuild the soil, and increase biodiversity. The Alliance believes that the benefits of clean drinking water and abundant recreation areas derived from the presence of Lake Belton in our community need not be at the expense of creating unproductive and eroded land.

Although revegetation of minespoil areas has been intensively studied, no information is available concerning the performance of various grasses on a severely disturbed site in Central Texas. The purpose of this study is to evaluate the persistence, yield, and spread of ten grass species on the excavated Miller Springs site. This information will be used by the Miller Springs Nature Alliance to formulate plans for the revegetation of the disturbed area.

Materials and Methods

Plant Materials Used

The ten grasses selected for testing represent tall and short native grasses as well as introduced rangeland grasses. Only species with commercially available seed were included in this study. Native species (indigenous to the region) included big bluestem (AaroPonon nerardi), little bluestem (Andrononon scoparius), 'Alamo' switchgrass (Panicum viroatum), 'Haskel' sideoats grama (Bouteloa curtipendula), indiangrass (Sorahastrum nutans), and buffalograss (Buchloe dactvioides). Research at the Grassland, Soil and Water Research Laboratory, USDA­ARS, Temple, Texas (Tischler, unpublished observations) has demonstrated that 'Alamo' is the best adapted commercially available switchgrass cultivar for the Central Texas area. 'Hachita' blue grama (Bouteloa aracilis) was also included in the study, although Central Texas would be at the extreme southern edge of its area of adaptation. 'Van Horn' green sprangletop (Leptochloa dubia), although generally not considered to be a component of prairie ecosystems, was included because of its adaptation to sandy or rocky sites in arid climates (Hitchcock, 1951). The same logic was used for including kleingrass (Panicum coloratum) and Cochise lovegrass (Eraarostis lehmanniana X E. trichonhora) in the study. Kleingrass is grown on over one million acres in West Central and Southwest Texas, and has been shown to be useful in revegetation of minespoil sites in Central Texas (Chichester and Hauser, 1984, 1991). Cochise lovegrass is an important forage grass on sandy soils in New Mexico and Arizona (Voigt, et al. 1987).

Soil Properties

Two soil samples were composited from several subsamples taken from one of the quadrants of the study site. Analyses were made by the Soil Testing Laboratory, Texas A&M University. By textural analysis soil of the study site is classified as a clay loam (24% sand, 34% clay, and 42% silt). Elemental analysis indicated the soil is very low in nitrogen (4 lb per acre in the top six inches). Although phosphorous content was moderate (30 lb per acre in the top six inches), because of the relatively high soil pH (8.3), this element was probably largely unavailable.

Plot Establishment

In early spring of 1993, seed of all species was germinated and seedlings were transferred to 36­cell plastic flats. Plants were maintained in these flats until May of 1993, when they were transplanted into the field site at Miller Springs Nature Center. This field site had previously been tilled with a tractor­mounted tiller. No fertilizer was applied. The grass seedlings were planted and watered, and the area was subsequently fenced to limit pedestrian traffic. Several rains subsequent to planting allowed the transplants to become established, and no supplemental irrigation or fertilizer was applied to the plots. The experiment was divided into two replications with a randomized complete block design. For each grass, 6 X 6 foot blocks (each consisting of 16 plants on 2 foot centers) were planted. A buffer strip of six feet separated the different grasses.

Data Collected

Grasses were visually scored for vigor on April 1 and October 7 of 1994 and on April 11, 1995. Scoring was based on a subjective evaluation of how the grass appeared (in terms of biomass produced, tillering, and general vigor) on the site, with a score of 5 indicating the grass was vigorous and competitive, and a score of 1 indicating low vigor and probable disappearance over time.

Standing dead biomass was harvested on April 11, 1995 to give an indication of biomass accumulation during the previous year. Crown diameters were measured, to provide an indication of the amount of crown expansion during the course of the experiment.

A final evaluation of the plot was made on July 24, 1995. Number of living plants and a visual ranking of biomass was made at this time.

Results

Visual Scoring at Three Dates

Results of visual scoring averaged over the three dates are presented in Figure 1. Indiangrass, switchgrass, and Sideoats Grama consistently scored high. Green sprangletop consistently received a low score, with the remainder of the grasses being intermediate.

Standing Biomass Harvest, April 1995

Standing biomass of switchgrass was significantly greater than that of the other grasses (Table 1). Green sprangletop and Indiangrass were next in order, followed by Sideoats Grama and Cochise Lovegrass. Significantly lower biomass production was noted for the remaining grasses. Data was not collected for Buffalograss because of the very small amount of biomass present.

Crown Diameter. April 1995

Sideoats grama and Indiangrass exhibited a significant increase in crown diameter (Figure 2). The remainder of the grasses were all similar in crown diameter. Data is not included for buffalograss because of its sod­forming growth habit.

Fig 1. Mean visual ranking for vigor at three dates.

Graph under construction….

Final Evaluation, July 24. 1995

The plot area received little rainfall during July of 1995, and all grasses appeared water stressed at the July 24 observation. The switchgrass plots in each replication dominated the landscape. All of the original 32 plants (total of both replications) were alive and vigorous, and were flowering with inflorescence at a height of about three feet. Despite the relatively large amount of biomass produced by green sprangletop during the 1994 growing season, no living plants were observed in this evaluation. Cochise lovegrass, kleingrass, and blue grama plots were in poor condition (22, 27, and 22 plants remaining, respectively, of the 32 planted originally). The physical appearance of these grasses suggested they would disappear from the plots within another year. The buflalograss plots were brown, although much of the plant material was still alive. Competition from partridge pea and King Ranch bluestem was severe and these weedy species appeared to dominate the buffalograss plots. Indiangrass, little bluestem, and sideoats grama were all equivalent, with all initial plants still living. Big bluestem, although visually inferior to the three previously mentioned grasses, was superior to kleingrass, blue grama, and Cochise Lovegrass. All of the above grasses (indigenous to the region) were notable less vigorous on this site than at nearby sites with the original topsoil in place.

Fig. 2 Mean crown diameter per plant (cm), April, 1995.

Graph Under Construction

Discussion

The severe nutrient deficiencies of the soil at this site provided a rigorous test of the adaptability of these grasses. Perhaps the most revealing data were gathered in our final evaluation made on July 24, 1995. Green sprangletop had essentially disappeared. This is rather surprising, given the relatively high biomass yield of green sprangletop the previous year. However, these observations are consistent with reports suggesting that green sprangletop is rather short­lived (Alderson and Sharp, i 1994). Cochise Lovegrass, kleingrass, and blue grama were in poor condition. Our previous experience with these grasses suggest that they would not survive a severe winter in Central Texas. This is not unexpected for blue grama, because the test plot is south of its normal range of adaptability. However, the poor persistence and competitiveness of kleingrass was unexpected, because it performs well on minespoil sites in Central Texas (Chichester and Hauser, 1984, 1991). The poor performance of Cochise lovegrass also is not completely unexpected. Foy, et al. (1977) indicated that love grasses generally experience iron chlorosis and reduced vigor on calcareous soils. Also, Jordan (1981 ) indicated that Cochise is best adapted to coarse­textured (sandy) soils, rather than the clay loam present at the experimental site.The crown diameter measurements indicated that sideoats grama was successfully colonizing new soil areas better than the remainder of the grasses. This observation is especially significant in a disturbed site where seedling establishment would probably be very poor, and spreading by rhizomes or stolons would be a major mechanism of stand thickening. Indiangrass also exhibited significant increases in crown diameter, and would also be desirable as a component to use in revegetation for this reason.

Switchgrass consistently had the best visual rating. The fact that it is a tall grass may introduce some bias into this evaluation, however, the aesthetic value of a grass that "looks good" is a significant component of the judgement of whether a grassland restoration project was successful. Also, because switchgrass reaches a height of several feet, it competes successfully with King Ranch bluestem, partridge pea, and other weedy components of the flora of the site.

Although we did not critically measure seed production, a grassland revegetation project is successful only if the components propagate themselves. Thus seed production (in addition to increase in crown diameter) is important. Casual observations indicated that switchgrass was the best seed producer. This observation again demonstrates the utility of switchgrass as a potential species for revegetation of the site.

When considering the results of this study, one must recall that soil fertility was extremely low. Fertilizer additions may have made some of the poor performers more competitive. It is known that switchgrass responds well to fertilization (Sanderson, et al. 1995), and should exhibit correspondingly higher vigor when fertilized. The conversion of this disturbed site to a diverse community will require the accumulation of organic matter and the acquisition of nutrients for recycling between the decaying organic phase and the growing plant component. Also, the organic phase is essential because it increases water infiltration rate and improves soil physical properties. Results from a New York study (Choi and Wali, 1995) where switchgrass was established on old iron­mine tailings indicated that switchgrass successfully added organic matter, and elevated action exchange capacity and concentrations of nitrogen, phosphorous, and potassium on this site. The changes elicited by switchgrass in the New York study are also needed on the Miller Springs site. Obviously, this process could be accelerated by applying fertilizer and/or organic matter. As the ecosystem is currently functioning, our results indicate that switchgrass, sideoats grama, and Indiangrass can persist and increase in crown diameter. Big bluestem and little bluestem, although marginal in performance, apparently can also persist. Performance of grasses at this location when compared to those in other nutrient poor but relatively undisturbed sites may be less than optimum because of differences in soil microflora. Noyd, et al. (1995) have shown that growth of several native prairie grasses on iron ore tailings was significantly improved by the addition of appropriate arbuscular mycorrhizal fungi. The beneficial effect of the fungi was traced to a more efficient uptake and use of phosphorous, and the effect was most pronounced in big bluestem. Perhaps the expertise of a mycologist would be beneficial in directing the long­term rehabilitation of the Miller Springs site, as inoculation of the soil with the appropriate fungal species could potentially increase competitiveness of one or more of the grasses.

A critical question not addressed in this study is the capacity for seedling establishment of each of the successful species. Appropriate experiments to address this question should precede any major reseeding effort. However, if transplants were used, our data indicate that switchgrass, Indiangrass, and sideoats grama would successfully establish and serve as a seed source for further colonization in years where conditions for seedling establishment are suitable. Also, inputs of inorganic or organic nutrients could be expected to speed the conversion of this disturbed site into a self­sustaining grassland.

Literature Cited

Alderson, J. and W. C. Sharp, eds. 1994. Grass Varieties in the United States. Agriculture Handbook No. i70. U. S. Department of Agriculture. p.145.

Chichester, F. W., and V. L. Hauser. 1984. Revegetation of minesoils constructed from lignite overburden in East­Central Texas. Reclamation and Revegetation Research 3:137­152.

Chichester, F. W., and V. L. Hauser. 1991. Change in chemical properties of constructed minesoils developing under forage grass management. Soil Science Society of America Journal 55:451459

Choi, Y. D. and M. K. Wali. 1995. The role of Panicum virnatum (switchgrass) in the revegetation of iron­mine tailings in northern New York. Restoration Ecology 3:123­132

Foy, C. D., P. W. Voigt, and J. W. Schwartz. 1977. Differential susceptibility of weeping lovegrass strains to an iron­related chlorosis on calcareous soils. Agron. J. 69:491496.

Hitchcock, A. S. 1950. Manual of the Grasses of the United States. USDA Msc. Pub.

· 200. Government Printing Office. Washington, D. C.1051 pp.

Jordan, G. L. 1981. Range seeding and brush management on Arizona rangelands. Arizona Ag. Expt. Sta. Pub. T81121.

Noyd, R. K., F. L. Pfleger, and M. P. Russelle. 1995. Interactions between native prairie grasses and indigenous arbuscular mycorrhizal fungi: Implications for reclamation of taconite iron ore tailing. New Phytologist 129:651­660.

Sanderson, M. A., M. A. Hussey, W. R. Ocumpaugh, C. R. Tischler, J. C. Read, and R. L. Reed. 1995. Switchgrass research at the regional cultivar and management testing center. Proc. Biomass Conference of the Americas. (In Press).

Voigt, P. W., C. R. Tischler and B. A. Young. 1987. Selection for improved establishment in warm­season grasses. pp. 177­187. In Proc. Symp. Seed and Seedbed Ecology of Rangeland Plants, Tucson, AZ.

Table 1. Mean Standing Dry Biomass (per row of four plants) of Grass Plots,

Harvested April 1995.

Values not followed by the same lower case letter are significantly different at the 5% level' Duncan's Multiple Range Test.

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