Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. ‘ : \ . é 4 ‘ oe pe A99.9 F764Un Great Plains southwest >> ia a aq rary -\D'@"* Research Note RM-480 Oe. January 1988 USDA Forest Service Rocky Mountain Forest and Range Experiment Station Carbon Dioxide Evolution From an Organically Amended Rio Puerco Soil’ P. R. Fresquez, Earl F. Aldon and G. L. Dennis? As a result of organic matter application, microbial populations and activity (CO, production) increased significantly compared to an un- amended soil. Carbon dioxide evolution in the unamended soil did not increase with increases in the soil moisture content above 11% (-2 bars). This suggests that soil microbial activity may be limited more by the lack of organic matter rather than by soil moisture above — 2 bars. Of the four organic amendments studied, sewage sludge had more desirable effects on soil biotic and abiotic properties than the others. Keywords: Soils, soil amendments, range management. The Upper Rio Puerco Watershed in northwestern New Mexico has a long history of heavy grazing (Dortignac 1960, Sheriden 1981, Vincent 1984). Over- grazing reduces the amount of plant cover and litter, decreasing the amounts of soil organic matter and plant available nitrogen (Clark and Paul 1970, Woodmansee 1978). Many soils in the Upper Rio Puerco Watershed are low in soil organic matter and plant available nitrogen**°. These soils are usually low in fertility, have poor structure, and erode readily (Campbell 1968). Degraded semiarid rangeland soils may be improved by adding amendments designed to improve the soil chemical, physical and biological properties. Applica- tion of organic amendments is an inexpensive and environmentally acceptable method of improving soil productivity. Organics increase the amount of soil 'This research reported here was conducted in cooperation with the USDI Bureau of Land Management, which furnished funds and field study locations. ?Fresquez is Soil Microbiologist, Aldon is Research Forester, and Dennis is Graduate Research Assistant, Rocky Mountain Forest and Range Experiment Station, at the Station’s Research Work Unit in Albuquerque, N. Mex. Station headquarters is in Fort Collins, in coopera- tion with Colorado State University. 3Aldon, Earl F., D. G. Scholl, P. R. Fresquez, and R. E. Francis. 1987. Natural production potential of some Rio Puerco soils in New Mexico. Unpublished data. 4Fresquez, P. R., R. E. Francis, and G. L. Dennis. 1987. Fungal com- munities associated with phyto-edaphic communities in the semi-arid Southwest. Unpublished data. SWhitford, W., Earl F. Aldon, D. W. Freckman, Y. Steinberger, and L. W. Parker. 1987. The effects of organic amendments on soil biota on a degraded rangeland. Unpublished data. organic matter, as well as essential plant nutrients (Aldon et al. 1975, Terry et al. 1979). The decomposi- tion of organic substrates usually increases carbon dioxide production as soil microorganisms and their activities increase (Alexander 1977). The objective of this preliminary study was to gather information on the rela- tionships between different organic amendments and soil microbiological activity in order to determine which organic amendment(s) would be best suited for further study. Study Area and Methods Field plots were established on May 10, 1981, on a degraded semiarid plant community, approximately 14 km southeast of Cuba, New Mexico. The plant com- munity was classified as a snakeweed (Guiterrezia sarothrae)/galleta (Hilaria jamesii) - blue grama (Bou- teloua gracilis)/alkali sacaton (Sporobolus airoides) western wheatgrass (Agropyron smithii) type (Francis 1986). The chemical analysis of the soil associated with this plant community showed low organic matter (5.4 g/kg), ammonium (0.3 ug/g), nitrate (2 ug/g) and total nitrogen (200 ug/g) contents. The texture was a sandy clay loam, and the pH was 8.2. The experimental design was a randomized complete block design which included four blocks, each contain- ing five treatments. Each treatment plot was 5.95 m? and was separated by a 0.6-m buffer zone. Amendments were surface applied and included: (1) unamended (control), (2) anaerobically digested dried sewage sludge (22.4 Mg/ha), (3) composted dairy cattle manure (22.4 Mg/ha), (4) wheat straw (11.2 Mg/ha), and (5) woodchips (1 cm) (11.2 Mg/ha). An alkali trap method was used to measure microbial activity via CO, evolution (Fresquez 1981). Forty polyvinylchloride (PVC) tubes (two tubes per plot), 19 cm in diameter and 27 cm long were pushed 18 cm into the soil. A vial containing 20 mL of 0.5 N NaOH was placed into each tube on each of seven sampling periods. The tubes were sealed with plastic wrap and aluminum foil. Blanks were sealed on both ends of the tube and contained no soil. After 24 hours, the vials were removed and their contents were titrated. Titration in- cluded adding 3 drops of phenolphthalein indicator followed by 1 mL of saturated BaCl, and titrating slow- ly with 0.20 N HCI to the phenolphthalein endpoint. Data were collected from seven sampling dates during the summer growing season of 1981. Results are reported as) ciC@sam-ida Soil samples were collected (0 to 13 cm deep) and analyzed for aerobic heterotrophic bacteria, Strepto- myces and fungal propagules for each treatment on each of the seven sampling dates. Methods used for determin- ing the populations of bacteria, Streptomyces and fungal propagules have been described previously (Fresquez and Lindemann 1982). The populations of these micro- organisms were pooled (an average of the seven sam- pling dates) and reported as such on an oven-dry weight soil basis. Results and Discussion Chemical properties varied among the organic amend- ment materials (table 1). As expected, all the organic amendments had high organic matter contents, which ranged from 105 to 500 g/kg. Although the manure amendment had the highest organic matter content, it had a high electrical conductivity (EC) and sodium absorption ratio (SAR), which may inhibit soil micro- organisms (Fresquez and Lindemann 1982) and plant growth (Bohn et al. 1979). Sewage sludge, in contrast, had a lower EC and SAR compared to the manure amendment. Also, sludge contained the highest total N content, which resulted in a reduced C:N ratio (6) com- pared to the other amendments. Carbon to nitrogen ratios above 30 favor N immobilization (Alexander 1977). Manure, straw, and woodchips all have C:N ratios above 30 and can be expected to decay slowly. All of the organic amendment treatments had signif- icantly higher CO, production than the unamended soil on most sampling periods (table 2). Even on the first sampling period (4 days after treatment application), there were significantly higher CO, values observed in the manure treatment compared to the control treatment. The soil moisture content in the unamended control on the first sampling date (May 14) was 8% ( — 7 bars). With an increase in soil moisture to 11% ( - 2 bars) on June 3, mean CO, production increased two-fold in all treat- ments, including the control. Decomposition of the organic amendments doubled again when the moisture content increased to 32% (-1/3 bar) on July 1. Soil microbiological activity in the unamended control, however, did not increase with further increases in soil moisture above 11% (- 2 bars), indicating the limited microbial activity of this soil without amendment. On the last sampling date, September 4, the moisture content was 8% (-7 bars). The organic amendment treatments on this date all were significantly higher com- pared to the unamended control, and were significant- ly higher as a group (mean= 2.7 g m? d~') compared to the first May 14 sampling date (mean = 1.4 g m*?d~?), which also had a similar moisture content. This suggests that microbial activity after 4 months was occurring at a higher rate in amended treatments than in the un- amended treatment, even when the soil moisture con- tent was low (-7 bars). The sewage sludge treatment had significantly higher populations of bacteria compared to the other organic matter treatments and the unamended control (table 3). Streptomyces populations were not significantly dif- ferent between treatments. Significantly higher fungal populations were found in the straw and sludge treat- ments compared to the other organic treatments and the unamended control. Conclusions Soil microbiological activity, as measured by CO, evolution was limited by the lack of organic matter in unamended soil rather than by soil moisture above 11% (-2 bars). Moreover, when soil moisture was low (-7 Table 1.—Chemical properties associated with organic amendment materials. Water soluble cations' Phosphorus and nitrogen i Say a. 5 ee re Organic Treatments Na Ca Mg K P NH,-N NO,-N TKN pH EC SAR marie C:N ratio tte etre eee eee -- eee ug/g ---------------------- dS/m g/kg Sewage sludge 289 843 55 234 632 204 14 10600 7.22 6.57 2.62 105 6 Manure 939 21 17 4279 #1162 10 153 4190 857 15.40 37.20 500 69 Straw 51 46 16 1123 101 2 1 1520 7.95 3.45 1.66 375 143 Woodchips 12 21 6 121 2 7 1 520 5.74 0.53 0.58 293 327 ‘Water soluble cations, pH, and EC determined from saturated paste extract. Soil P, NH.-N, and NO,;-N determined from 1:5 water extract. Organic matter determined by the Walkley-Black method, and total nitrogen (TKN) determined by the macro-Kjeldahl procedure. Table 2.—Carbon dioxide evolution as affected by organic amendment in the field during the growing season of 1981. Sample dates Treatment 5/14 6/3 6/17 7/21 7/16 8/12 9/4 we eee eee ee eee eee eee g CO, m*¢d-'------------------------ Unamended (control) 1.20b' 2.60b 1.15d 2.34d 1.52c 2.22d 1.64b Sludge (22.4 Mg/ha) 1.28b 2.77a 1.64b 6.66a 3.62a 5.90a 2.38a Manure (22.4 Mg/ha) 1.63a 2.79a 1.41be 4.78bc 3.68a 4.68b 2.50a Straw (11.2 Mg/ha) 1.46ab 2.82a 1.90a 4.96b 3.63a 4.66b 2.30a Woodchips (11.2 Mg/ha) 1.35ab 2.77a 1.37cd 4.33c 2.50b 3.55c 2.224 'Means within the same column followed by the same letter are not significantly different at the 0.05 level by the Least Significant Difference (LSD) test. Table 3—Soil microbial populations as affected by organic amendment.' Aerobic heterotrophic Fungal Treatment bacteria Streptomyces propagules Pe At eR? ey 10° g-'-------- 1103 gia! Unamended (control) 20b? 4.9 43b Sludge (22.4 Mg/ha) 464a 14.0 458a Manure (22.4 Mg/ha) 39b 9.4 112b Straw (11.2 Mg/ha) 57b 10.7 774a Woodchips (11.2 Mg/ha) 26b 8.5 98b 'Values are an average of seven sampling dates. 2Means within the same column followed by the same letter are not significantly different at the 0.05 level by the Least Significant Difference (LSD) test. bars), CO, production in organic treatment soils was higher than in unamended soil. Of the organic amend- ments, sewage sludge had higher microbial populations and CO, activity than the others; this was probably a result of the lower C:N ratio compared to the other organic amendments. Sewage sludge warrants further research, in terms of application rates, microbial popula- tions and activities, soil nutrients and moisture, and plant production and quality responses occurring on degraded semiarid rangelands. Literature Cited Alexander, M. 1977. Introduction to Soil Microbiology. Wiley, New York, New York. Aldon, E. F., H. W. Springfield, and G. Garcia. 1975. Can soil amendments aid revegetation of New Mex- ico coal mine spoils. USDA Forest Service Research Note RM-292, 7 p. Rocky Mountain Forest and Range Experiment Station, Fort Collins, Colo. Bohn, H., B. McNeal, and G. O'Conner. 1979. Soil Chemistry. Wiley Interscience, New York, New York. Campbell, R. E. 1968. Production capabilities of some Upper Rio Puerco soils of New Mexico. USDA Forest Service Research Note RM-108, 7 p. Rocky Mountain Forest and Range Experiment Station, Fort Collins, Colo. Clark, F. E., and E. A. Paul. 1970. The microflora of grassland. p. 375-426. In: Advances in Agronomy, Volume 22, N. C. Brady, editor. Academic Press, New York, N. Y. Dortignac, E. J. 1960. The Rio Puerco-past, present, and future. New Mexico Water Conference Proceedings, 5:45-51. Francis, R. E. 1986. Phyto-edaphic communities of the Upper Rio Puerco Watershed, New Mexico. USDA Forest Service Research Paper RM-272, 73 p. Rocky Mountain Forest and Range Experiment Station, Fort Collins, Colo. Fresquez, P. R. 1981. Microbial populations of amended coal mine spoils and surface soil. M.S. thesis. New Mexico State University, Las Cruces. 95 p. Fresquez, P. R., and W. C. Lindemann. 1982. Soil and rhizosphere microorganisms in amended coal mine spoils. Soil Science Society of America Journal, 46:751-755. Fresquez, P. R., and W. C. Lindemann. 1983. Green- house and laboratory evaluations of amended coal- mine spoils. Reclamation and Revegetation Research, 2:205-215. Sheriden, D. 1981. Desertification of the United States. U.S. Goverment Printing Office, Washington, D.C. 142 p. Terry, R. E., D. N. Nelson, and L. E. Sommers. 1979. Carbon cycling during sewage sludge decomposition in soils. Soil Science Society America Journal, 43:494-499. Vincent, D. 1984. Range trends in the Cabezon area. Rangelands, 6:120-122. Wollum, A. G. 1982. Cultural methods for soil micro- organisms. p. 781-802. In: Methods of Soil Analysis, Part 2. A. L. Page, R. H. Miller, and D. R. Keeney, editors. American Society of Agronomy, Madison, Wisconsin. 1159 p. Rocky Mountains a Southwest Great Plains U.S. Department of Agriculture Forest Service Rocky Mountain Forest and Range Experiment Station The Rocky Mountain Station is one of eight regional experiment stations, plus the Forest Products Laboratory and the Washington Office Staff, that make up the Forest Service research organization. RESEARCH FOCUS Research programs at the Rocky Mountain Station are coordinated with area universities and with other institutions. Many studies are conducted on a cooperative basis to accelerate solutions to problems involving range, water, wildlife and fish habitat, human and community development, timber, recreation, protection, and multiresource evaluation. RESEARCH LOCATIONS Research Work Units of the Rocky Mountain Station are operated in cooperation with universities in the following cities: Albuquerque, New Mexico Flagstaff, Arizona Fort Collins, Colorado’ Laramie, Wyoming Lincoln, Nebraska Rapid City, South Dakota Tempe, Arizona *Station Headquarters: 240 W. Prospect St., Fort Collins, CO 80526