UNIVERSITY OF WISCONSIN SYSTEM SOLID WASTE RESEARCH PROGRAM

Size: px

Start display at page:

Download "UNIVERSITY OF WISCONSIN SYSTEM SOLID WASTE RESEARCH PROGRAM"

Leslie Cox
5 years ago
Views:

Subsoil for Stabilization of Non-Metallic Mine Sites 2005 Dr.

1 UNIVERSITY OF WISCONSIN SYSTEM SOLID WASTE RESEARCH PROGRAM Artificial Topsoil Mix Prepared with Papermill Fiber Residuals And Subsoil for Stabilization of Non-Metallic Mine Sites 2005 Dr. Richard Wolkowski Department of Soil Science University of Wisconsin-Madison

2 Artificial Topsoil Mix Prepared with Papermill Fiber Residuals and Subsoil for Stabilization of Non-Metallic Mine Sites Richard Wolkowski Associate Scientist Department of Soil Science University of Wisconsin Madison A Final Report for the Stora Enso North America 5 January 2005 Introduction: Concerns with the status of abandoned non-metallic mining sites resulted in the development Chapter NR 135 of the Wisconsin Administrative Code that became effective in December This code created a uniform standard for reclamation, a large part of which is the establishment of adequate vegetative ground cover to prevent soil erosion. Many mine sites lack sufficient amounts of quality topsoil for re-vegetation. Subsoil materials are typically scraped and stockpiled prior to removing the mined resource and are often available on site. Most subsoil materials are infertile, lack organic matter, contain stones and clay, and may have a ph poorly suited to plant growth. Therefore, it is conceivable that certain organic waste materials could be blended with the subsoil to supply plant nutrients and improve tilth, creating inexpensive artificial topsoil suitable for remediation of these sites. Papermill residuals (PMR) represent one of the largest, if not the largest, sources of organic waste material in Wisconsin. Currently, most of this material is landfilled for economic reasons and the fact that few alternative uses exist. Stora Enso North America (SENA) has developed successful agricultural land spreading programs (e.g. ConsoGro) for materials produced by some of their facilities. These have been very beneficial for low organic matter sandy soils and have been well received by farmers. The SENA mill at Kimberly produces approximately 109 wet tons of residual per day (Andy Gilbert, personal communication). This material consists of primary and secondary sludge that are blended and dewatered with a screw press to a solids content of about 48.5 %. A recent nutrient analysis of the material shows minimal inorganic N, 7600 ppm total (Kjeldahl) N, 1600 ppm P, ppm Ca, and small amounts of other plant nutrients. This report describes the findings of a field study collected in 2003 and 2004 near the City of Kiel on a site that is intended to simulate conditions following the mining of gravel.

3 Objective: The main objective of this study was to determine the blend ratio of papermill residual, subsoil, and inorganic N fertilizer that optimizes plant growth. This mixture would have the potential for offering adequate ground cover for mine site remediation shortly after seeding and sustaining growth following establishment. Methods and Materials: A study site was provided by the owner of Kiel Sand and Gravel in a small portion of a 40-acre tract approximately three miles east of the City of Kiel, Wisconsin. The site was relatively gravely, had very little topsoil, and was vegetated with goldenrod, canada thistle, common ragweed, and other weed species. The SENA Kimberly Mill supplied the PMR and subsoil was collected from an active pit adjacent to the site. Kiel Sand and Gravel provided mechanical assistance for the on-site mixing and application of the artificial soil blends. The PMR used in a previous greenhouse study had a total N content of 0.76 %, solids content of 48.5 % and an estimated C:N of 32 %. The subsoil material was found to have a silty clay texture (6% sand, 46% silt, and 48% clay). The UWEX routine soil test of the material at the time of collection was ph 8.2, organic matter 1.0 %, available Bray P 1 of 6 mg/kg, and exchangeable K of 62 mg/kg. Materials were initially applied and the site was seeded in September Because of dry conditions that fall, which led to poor plant growth, the site was re-worked and re-seeded into the existing material blends on 4 June Broadcast applications of 100 lb P 2 O 5 /a and 100 lb K 2 O/a were made prior to both the 2002 and 2003 seeding. A split-plot design with three replications was established. The main plot was blend ratio (0, 10, 20, and 40 % PMR:subsoil on a dry weight basis). Blend ratios were created by calibrating the weight of material in a full bucket of a payloader and then mixing appropriate proportions of the materials in piles with this equipment. The materials were transported to the plot area and smoothed with a small tractor-mounted roto-tiller to create an artificial soil depth of approximately one foot over the existing grade. Nitrogen fertilization was the subplot. Either none or 100 lb N/a as ammonium nitrate was broadcast to the plots prior to seeding. This treatment had also been applied the previous September to the failed seeding. A mixture of 20 lb smooth bromegrass (variety not stated), 10 lb timothy ( Climax ), and 8 lb vernal alfalfa was seeded by hand uniformly over the plot area and was incorporated with a spike tooth drag pulled by hand over the site. Measurements taken included: 1) soil bulk density and gravimetric water content for the 0-3 and 3-6 in. depth on 23 July 2003; 2) percent alfalfa for the stand on 23 July 2003 and 18 June 2004 and percent ground cover on 23 July 2003; 3) total dry matter accumulation at harvest on 19 August 2003, 18 June 2004, and 18 August 2004; 4) soil nitrate-n for the 0-6 in. depth on 23 July 2003 and 18 August 2004; and, 5) routine soil test for the 0-6 in.

4 depth on 23 July 2003 and 18 August All soil and plant samples were analyzed according to the procedures of the UWEX Soil Testing and Plant Analysis Laboratory. Data were analyzed with an analysis of variance for a split-plot design using the methods of the Statistical Analysis System (SAS). Blend ratio was the main plot and N fertilization was the subplot. Pr>F values less than 0.05 would be considered to be statistically significant. Results and Discussion: Data for the dry matter accumulation measured in both 2003 and 2004 are shown in Table 1. These were collected with a flail mower mounted on a garden tractor that cut a 3 x 20 ft. swath through the plots. Chopped forage was deposited in a box where it was mixed and sampled for dry matter determination and chemical analysis prior to weighing the material. There were significant responses to blend mix ratio in 2003 and the first cut of Dry matter differences were not significant in the second cut of As the percentage of PMR increased in the blend the dry matter yield decreased. This could suggest N immobilization because of the relatively high C:N of the material, but could also be related to un-defined phytotoxic compounds in the PMR, or changes in the physical condition of the growing media by the blends that suppressed growth. By the end of the 2004 season it would be speculated that these effects were minimized. Nitrogen immobilization appeared to be the most likely cause of the reduced growth because of the subsequent increase where N fertilizer was applied. The response to N was not as distinct in the second cutting of Overall the application of N fertilizer nearly doubled the dry matter accumulation in 2003, with this difference diminishing during the 2004 season. The yield at the 20% blend with fertilizer appears anomalously high when compared to the 10% blend treatment for dry matter and several other measurements. It was initially thought that treatments were either misplaced in the field or that the plot diagram was inaccurate. Analyses of other measurements (e. g. soil organic matter content, bulk density, water content) show the expected trend for the treatment. No clear explanation for this response is obvious. An important consideration of the recent code is the requirement for ground cover that would absorb raindrop impact and stabilize the soil thereby reducing erosion. Because of the expected concern of N immobilization alfalfa was added to the seeding mix to determine if the N fixed by this species would sustain the stand better than a grass mix alone. Table 2 shows the percentage of alfalfa in the stand as visually estimated by three independent evaluators. Percentage alfalfa increased as the PMR increased in the blend, presumably because inadequate N was available to sustain the grasses. Likewise adding N fertilizer reduced the percentage of alfalfa in the stand. This difference was still obvious in 2004, except that the amount of alfalfa in the stand of the 20% treatment was substantially decreased. Even though the 40% PMR was essentially pure alfalfa in 2003 the total dry matter with this treatment was very low compared to other blend and N fertilizer treatments. However by the second harvest in 2004 the 40% treatment that had received N fertilizer had the highest dry matter yield of any treatment. Table 3 shows that initially the 40% PMR blend produced an inadequate amount of ground cover (avg. 49%) compared to the lower blends. Growth was more stunted in this treatment compared to

5 the other blends. Ground cover measurements were not taken in 2004 because an inspection of the site showed that all treatments would have exceeded 90% cover. Adding N fertilizer always increased ground cover because it encouraged the growth of grass in the stand. The influence of the blends and N fertilization on soil physical properties is shown in the effect on soil bulk density and the gravimetric water content. These data are shown in Tables 4 and 5, respectively. Measurements were only taken in Adding a large amount of a relatively lighter organic material clearly reduced the bulk density of the artificial soil. These changes were relatively consistent at both the 0-3 and 3-6 in. depth. Nitrogen fertilization tended to reduce the bulk density, especially in the 3-6 in. depth, which may be a response to the increased root growth or improved soil aggregation from enhanced biological activity. The gravimetric water content was substantially increased with the increase in PMR in the blend. These measurements were taken during a dry period in July and the values for the un-amended soil were likely near the wilting point for this soil. Adding organic material increased the water content that might better support plant growth, although the amount of this additional water that was plant available cannot be determined from these measurements. The effect of the blend treatments and N fertilization on the soil test levels measured in the 0-6 in. layer in July 2003 and August 2004 are shown in Tables Table 6 shows that soil nitrate-n was affected by both treatment variables in 2003, but no differences were observed in Adding any amount of PMR significantly reduced the concentration of Nitrate-N, supporting the hypothesis of N immobilization. Adding N fertilizer increased the N budget of the system, thereby providing a better growing condition for the grasses. The use of N fertilizer at establishment would be strongly recommended if these treatments were used in the actual implementation of the practice. Soil ph increased with the 40% PMR treatment in 2003, however the differences in ph were not as evident in Relatively speaking the soil ph level was very high in all treatments due to the alkaline nature of the soil material (Table 7). Nitrogen fertilization did not affect soil ph. Available P was relatively high for this soil and was increased by the addition of PMR (Table 8). This is especially true since the UWEX Soil and Plant Analysis Laboratory measure P with the Bray P1 test, which is known to under-estimate available P on alkaline soils. Phosphorus fertilization was likely not essential for this situation and underscores the need to follow fertilizer recommendations. Table 9 shows that soil test K was not affected by either treatment in 2003, and was inconsistently affected by blend ratio in The level of K in the material was likely adequate for the growth of the grasses and alfalfa and likewise K fertilization would not have been needed to establish the stand. Higher K recommendations are given for farm fields where forage production must be maximized. Table 10 shows that soil organic matter increased as expected with the increase of PMR in the blend. Results were not appreciably different in 2004, which would have been 14 months after application. Soil organic matter is determined by the loss on ignition method and un-decomposed PMR was visible in the collected samples. The OM where no PMR was added may be artificially high because of

6 CO 2 loss during ignition from free carbonates that may have existed in the soil because of the high ph. The elemental composition for the forage harvested in August 2003 is shown in Table 11. It is surprising that the N in the forage was not affected by treatment. The lack of response due to blend may reflect a late flush of N that was released where material was added, which increased the N level in the plants. Nitrogen fertilization increased the N content of the plant tissue, but not at the p=0.05 level. The addition of PMR affected the concentration of the other macro-nutrients (P, K, Ca, Mg, S) in the forage, although there was not a consistent trend relative to percentage PMR. The micro-nutrients and other elements were in general unaffected by PMR blend, other than Mn, which increased in concentration in the plant tissue as the PMR ratio increased. Where N fertilization affected elemental concentration there was typically a reduction in concentration. This suggests a dilution effect of the element in a larger amount of dry matter. The elemental composition of the forage harvested in June and August 2004 is shown in Tables 12 and 13, respectively. Although the N concentration in the June cutting was significantly affected by blend ratio a trend for the response is not obvious. Nitrogen fertilization reduced the N concentration in both the cuttings. This response may be due to the fact that a greater percentage of alfalfa was present in the unfertilized treatments, which increased the N concentration in the forage. The concentrations of the macro-nutrient elements in the forage harvested in 2004 were typically affected by blend ratio, although discernable trends were not obvious. The 20% treatment which had anomalous results for yield and alfalfa percentage also commonly had unexpected elemental concentrations. Similar significant responses were found for Zn and B. The other micro-nutrients were generally not affected by blend in Summary: A field study was conducted to evaluate the growth response of a grass-legume mix planted in an artificial soil created for non-metallic mine-site stabilization. The soil was composed of various blends of alkaline subsoil and papermill residual. Increasing the proportion of the PMR blend reduced forage dry matter accumulation and ground cover, presumably because of N immobilization in the year of establishment. The vegetative dry matter production responded to N fertilization and this practice would be recommended in the early period of establishment. Crop response to P and K fertilization in this situation were unlikely because of the relatively high content in the subsoil and addition from the PMR and therefore soil testing should be used to determine the need for these nutrients prior to establishment. The PMR improved soil physical properties that would support plant growth. The higher PMR blends had a lower soil bulk density and higher water content. The PMR treatments had a profound, but inconsistent effect on forage nutrient concentration. An artificial soil created from relatively low (<20%) blends of PMR and subsoil appears to be a reasonable practice for re-vegetating mine non-metallic sites, or other disturbed areas in eastern Wisconsin. While various seeding mixes were not evaluated in this study, it would be recommended that alfalfa, or a similar legume

7 forage species, be included in the seeding mix to help establish ground cover under high C:N conditions. Table 1. Dry matter production of a grass/legume forage as affected by artificial topsoil mix and N fertilization, Kiel, Wis., 2003 and Cut Cut Cut 2. Blend Ratio - N + N - N + N -N + N % PMR Dry Matter (tons)/acre Blend <0.01 < N < Blend*N <0.01 Table 2. Estimated percentage of alfalfa in the stand following seeding with a grass/legume forage mix as affected by artificial topsoil mix and N fertilization, Kiel, Wis., 2003 and Blend Ratio - N + N - N + N % PMR visual rating (%) Blend <0.01 <0.01 N <0.01 <0.01 Blend*N 0.03 <0.01 Average of visual assessment by three individuals.

8 Table 3. Estimated percentage ground cover in the stand following seeding with a grass/legume forage mix as affected by artificial topsoil mix and N fertilization, Kiel, Wis., Blend Ratio - N + N. % PMR - visual rating (%) Blend <0.01 N 0.01 Blend*N 0.78 Average of visual assessment by three individuals. Table 4. Soil bulk density (0-3 and 3-6 in.) following seeding with a grass/legume forage mix as affected by artificial topsoil mix and N fertilization, Kiel, Wis., in. 3-6 in.. Blend Ratio - N + N. - N + N % PMR g/cm Blend <0.01 <0.01 N Blend*N

9 Table 5. Gravimetric water content (0-3 and 3-6 in.) following seeding with a grass/legume forage mix as affected by artificial topsoil mix and N fertilization, Kiel, Wis., in. 3-6 in.. Blend Ratio - N + N. - N + N % PMR % Blend 0.01 <0.01 N Blend*N Table 6. Soil nitrate-n (0-6 in.) following seeding with a grass/legume forage mix as affected by artificial topsoil mix and N fertilization, Kiel, Wis., 2003 and Blend Ratio - N + N - N + N % PMR ppm Blend N < Blend*N <

10 Table 7. Soil ph (0-6 in.) following seeding with a grass/legume forage mix as affected by artificial topsoil mix and N fertilization, Kiel, Wis., Blend Ratio - N + N - N + N % PMR Blend < N Blend*N Table 8. Available soil P (0-6 in.) following seeding with a grass/legume forage mix as affected by artificial topsoil mix and N fertilization, Kiel, Wis., Blend Ratio - N + N - N + N % PMR ppm Blend < N Blend*N

11 Table 9. Available soil K (0-6 in.) following seeding with a grass/legume forage mix as affected by artificial topsoil mix and N fertilization, Kiel, Wis., Blend Ratio - N + N - N + N % PMR ppm Blend N Blend*N Table 10. Soil organic matter (0-6 in.) following seeding with a grass/legume forage mix as affected by artificial topsoil mix and N fertilization, Kiel, Wis., Blend Ratio - N + N - N + N % PMR % Blend < 0.01 <0.01 N Blend*N

12 Table 11. Elemental concentration of a legume-grass mixture planted on an artificial soil made with subsoil clay and papermill residuals, Kiel, Wis., Treatment N P K Ca Mg S Zn B Mn Fe Cu Al Na % ppm Blend LSD NS NS NS 20.5 NS NS NS NS Nitrogen No Yes LSD NS NS 3.5 NS 155 NS 184 NS Significance (Pr>F) Blend 0.40 <0.01 <0.01 <0.01 < < Nitrogen 0.09 < <0.01 <0.01 < < < B*N

13 Table 12. Elemental concentration of a legume-grass mixture planted on an artificial soil made with subsoil clay and papermill residuals, Kiel, Wis. (harvested 18 June 2004) Treatment N P K Ca Mg S Zn B Mn Fe Cu Al Na % ppm Blend , LSD NS 2 6 NS 15 NS NS 60 Nitrogen No Yes LSD NS NS 14 NS Significance (Pr>F) Blend 0.02 <0.01 <0.01 <0.01 < <0.01 < < <0.01 Nitrogen < <0.01 < <0.01 < < B*N 0.99 < <

14 Table 13. Elemental concentration of a legume-grass mixture planted on an artificial soil made with subsoil clay and papermill residuals, Kiel, Wis. (harvested 18 August 2004) Treatment N P K Ca Mg S Zn B Mn Fe Cu Al Na % ppm Blend LSD NS NS 7 9 NS NS NS NS 65 Nitrogen No Yes LSD NS NS 2 NS NS NS NS NS Significance (Pr>F) Blend <0.01 < <0.01 Nitrogen 0.04 < <0.01 < B*N <

High Carbon Wood Fly Ash as a Biochar Soil Amendment

High Carbon Wood Fly Ash as a Biochar Soil Amendment Preliminary Assessment Completed by Northern Tilth June 2010 Executive Summary Resource Management, Inc. (RMI) recycles wood ash from biomass plants