Robert B. Harrison

Liming effects on availability of Cd, Cu, Ni and Zn in a soil amended with sewage sludge 16 years previously

A field study was conducted to determine the plant uptake of metals in soils amended with 500 Mg ha−1 of municopal sewage sludge applied 16 yr previously. Results showed that metals were available for plan uptake after 16 yr, but that liming greatly reduced the plant availability of most metals. The application of sludge also resulted in high rates nitrification and subsequent lowering of the soil pH before the uptake study was started. The sludge-amended soil (a mesic Dystric Xerochrept) was adjusted with lime one month prior to planting from an unlimed pH of 4.6 to pH 5.8, 6.5 and 6.9. Food crops grown were: (i) bush bean (Phaseolus vulgaris L. cv. Seafarer), (ii) cabbage (Brassica oleracea L. v. capitata L. cv. Copenhagen market), (iii) maize (Zea mays L. cv. FR37), (iv) lettuce (Lactuca sativa L. cv. Parris Island, (v) (Solanum tuberosum L. cv. (vi) tomato (Lycopersicum esculentum L. cv. Burpee VF). With the exception of maize, yields were significantly reduced in the unlimed sludge-amended soil. However, liming increased yields above the growth level of the unlimed untreated soil for cabbage, maize, lettuce, potato tuber and tomato fruit. Soluble and exchangeable of Cd. Ni and Zn were also reduced after liming the sludge-amended soil. In both limed and unlimed soils, the majority of the soil Cu was found in insoluble and unavailable soil fractions. To evaluate trace metal uptake, the edible portion of each crop was analyzed for Cd, Cu, ni and Zn. Liming redoced uptake of Cd, Ni and Zn in most crops, but generally did not change Cu, This study shows the benefit of pH adjustment in reducing relative solubility and plant uptake of metals as well as increasing crop yield in acid soils.

Effect of spacing on growth and biomass distribution in Eucalyptus camaldulensis, E. pellita and E. urophylla plantations in southeastern Brazil

Abstract The growth and biomass accumulation in different plant parts (including root systems) of Eucalyptus camaldulensis, E. urophylla and E. pellita planted at three spacings (3×1.5 m, 3×3 m and 4×3 m) and three ages (15, 31 and 41 months) were evaluated in the savannah region of central Minas Gerais state in southeastern Brazil. A series of equations were produced to estimate per-tree biomass from age, spacing, diameter and height, and per-hectare biomass using age, spacing and a tally of tree diameters and heights. Average total productivity at age 41 months was of the order E. urophylla>E. pellita≥E. camaldulensis. As spacing increased, individual stems increased in diameter and total biomass; however, total biomass production per hectare decreased. Eucalyptus urophylla had 64.8 vs. 42.8, E. pellita 41.3 vs. 28.9 and E. camaldulensis 35.1 vs. 26.9 Mg ha−1 at 3×1.5 vs. 4×3 m spacings, respectively. Increased spacing levels also decreased the relative amount of growth allocated to the bole of the tree for E. urophylla and E. camaldulensis during the time period of this study and increased allocation to the root system, while E pellita showed relatively small changes. Allocation to the bolewood in E. urophylla changed from 46 to 36%, in E. camaldulensis from 37 to 32%, and E. pellita from 31–34% at 3×1.5 vs. 4×3 m spacings, respectively. Allocation to the root system in E. urophylla changed from 23–30%, in E. camaldulensis from 34–45%, and E. pellita from 37–33% at 3×1.5 vs. 4×3 m spacings, respectively. Thought these results show that some of the biomass changes from species, age and spacing differences are related to distribution, not total biomass production, there were significant differences in total biomass accumulation also. Since larger root systems may increase future yields from coppice growth, the effect of differences in allocation to the root system on future productivity needs to be evaluated.

Current status, uncertainty and future needs in soil organic carbon monitoring☆

Increasing human demands on soil-derived ecosystem services requires reliable data on global soil resources for sustainable development. The soil organic carbon (SOC) pool is a key indicator of soil quality as it affects essential biological, chemical and physical soil functions such as nutrient cycling, pesticide and water retention, and soil structure maintenance. However, information on the SOC pool, and its temporal and spatial dynamics is unbalanced. Even in well-studied regions with a pronounced interest in environmental issues information on soil carbon (C) is inconsistent. Several activities for the compilation of global soil C data are under way. However, different approaches for soil sampling and chemical analyses make even regional comparisons highly uncertain. Often, the procedures used so far have not allowed the reliable estimation of the total SOC pool, partly because the available knowledge is focused on not clearly defined upper soil horizons and the contribution of subsoil to SOC stocks has been less considered. Even more difficult is quantifying SOC pool changes over time. SOC consists of variable amounts of labile and recalcitrant molecules of plant, and microbial and animal origin that are often operationally defined. A comprehensively active soil expert community needs to agree on protocols of soil surveying and lab procedures towards reliable SOC pool estimates. Already established long-term ecological research sites, where SOC changes are quantified and the underlying mechanisms are investigated, are potentially the backbones for regional, national, and international SOC monitoring programs.

Use of municipal sludge to restore and improve site productivity in forestry: The pack forest sludge research program

Abstract Municipal wastewater residuals—sludge or biosolids—represent a major waste by-product from society that must be managed in responsible ways, and not released into aquatic systems or allowed to contaminate ground waters. Because of its high nutrient and organic matter content, sludge can be beneficially recycled into forest sites for site improvement purposes. Research to date on forest application of sludge has been very encouraging, clearly demonstrating the validity of this management technique. Forest sites typically display benefits in two ways: (1) an immediate growth response by both overstory and understory species; (2) a long-term improvement to the productivity of the site. However, for this practice to have broad utility and acceptance, it is critical that the concerns of the regulatory agencies and general public be addressed regarding public health and environmental issues through continued research. These concerns include the fate of trace metals, including movement, uptake and potential phytotoxicity, and passage into wildlife and human food cahin, the fate of pathogens, and leaching of nitrates into ground water systems. Many concerns are a result of misconceptions or misunderstandings of the potential problems involved and require working with these agencies and the general public through education and demonstration programs. This paper addresses the opportunities and problems that researchers at the University of Washington, College of Forest Resources have encountered while working in forest sludge applications during the past 20 years.

Additional carbon sequestration following repeated urea fertilization of second-growth Douglas-fir stands in western Washington

We examined whether N fertilization of Douglas-fir (Psuedotsuga menziesii (Mirb.)) plantations in western Washington State could affect C sequestration in both the vegetation and soils. Three sites, which received a total of 896‐1120 kg ha ˇ1 over a 16-year-period, were compared with adjacent unfertilized control sites. Carbon contained in the soil, understory vegetation and snags was measured in 1993. Since the tree biomass started at different levels (treated versus controls), C biomass and increment was analyzed dynamically from 1969‐1993. There was 6.2% more C (8 Mg ha ˇ1 ) stored in the sum of non-tree components, but the difference was not statistically significant. The N treatment added an average of 26.7 Mg ha ˇ1 (significant at 0.01 level) to the live tree component. On average, the entire forest system of the fertilized plots added 34.7 Mg Ch a ˇ1 . When considered individually, there was no significant difference between the amount of C stored in the snags, understory vegetation and all sampled soil horizons and depths to 85 cm in the control and fertilized plots. However, the ureatreated plots did contain on average 34% more C in the O horizon (20 versus 15 Mg of C ha ˇ1 ). A large portion of the soil C was found in deeper horizons. When sampling to a depth of 85 cm, 75% of soil C was found below the A horizon and 40% below 25 cm. This result illustrates how failing to sample below surface horizons can cause soil C to be underestimated in these forest ecosystems. However, these soil layers changed little in C concentration due to the treatment. This study suggests that N fertilization of commercial forests in western Washington could increase C stored in these forest ecosystems, though the absolute effect of widespread fertilization on stands of varying properties was not evaluated in this study. # 2000 Elsevier Science B.V. All rights reserved.

Long-term effects of heavy applications of biosolids on organic matter and nutrient content of a coarse-textured forest soil

Abstract Long-term changes in soil properties due to a single heavy application of municipal biosolids (municipal sewage sludge) on a coarse-textured glacial outwash soil were evaluated. Study sites, located at the University of Washingtons Pack Experimental Forest, 100 km south of Seattle, were clearcut, cleared, fertilized with 500 Mg ha −1 of municipal biosolids and planted a variety of tree species in 1975. Soil samples were taken in 1990 from three biosolids-amended forest stands and adjacent unamended control sites by horizon to a depth of 185 cm. Biosolids-amended samples had higher C (139 vs. 67 mg g −1 ), N (12 vs. 3.4 mg g −1 ), P (14 vs. 2.2 mg g −1 ) and S (2.5 vs. 0.4 mg g −1 ) contents in 0–7 cm mineral soil and other surface soil horizons compared with adjacent unamended soil horizons, but showed no significant differences below 25 cm. Soil pH ranged from 0.4 to 1.0 units lower in biosolids-amended vs. unamended soil throughout the sampled soil horizon. Soil cation exchange capacity was higher in the surface soil horizons (30 vs. 18 mmol c kg −1 in 0–7 cm soil), but there were no significant differences below 50 cm. Biosolids-amended samples had higher total Ca (13 vs. 6.1 mg g −1 in 0–7 cm soil) and K (1.9 vs. 1.5 mg g −1 in 0–7 cm soil) throughout the sampled soil profile. Total Mg was relatively constant (2.0–3.0 mg g −1 ) throughout the sampled soil profile. Study results indicate that one of the primary objectives of the original biosolids application (increasing total nutrients in the rooting zone of the forest soil) extended at least 15 years from the application date.

Analysis of sulfur in soil, plant and sediment materials: Sample handling and use of an automated analyzer

Abstract Methods for analyzing soil, vegetation and sediment samples for total S and handling soil samples for analysis of S constituents were examined. A LECO automated total S analyzer (SC-132) was used for the analysis of vegetation, sediments and soil samples. Results from the LECO analyzer compared favorably with other currently used total S techniques such as alkaline oxidation. Calibrating the instrument on soil or vegetation standards using two combusion accelerators improved accuracy and recovery. The upper 99% confidence interval RSD values for duplicate samples using the LECO analyzer were

Measuring the cation exchange capacity of forest soils

Various methods have been proposed for assessing the cation exchange capacity (CEC) of soils. A pH 7 buffered ammonium acetate solution is the most widely used method but its use for forest soils has been questioned as it may result in an overestimation of CEC in soils with pH dependent charges. The objective of this study was to determine the most appropriate method for measuring the natural CEC of forest soils using variations of 3 common methods. These methods included: (1) pH 7 buffered ammonium acetate (2) unbuffered 1.0, 0.5, and 0.1 M ammonium chloride, and (3) the compulsive exchange method using the original method and with magnesium chloride. The CEC of three reference materials (kaolinite, vermiculite and humified organic matter) was predetermined and used for comparison. In addition, samples from the major genetic horizons of 8 soils from Washington State, USA, the North Island, New Zealand, and Indonesia were analyzed for CEC. Results showed that the compulsive exchange method resulted in consistently low CEC values, and did not reflect changes in soil organic matter or pH. The pH 7 buffered ammonium acetate resulted in artificially high CECs in soils high in organic matter and low pH, undoubtedly due to increases in pH dependent charges. Although the 0.5 and 0.1 M NH4Cl would work well for many forest soils, there may be insufficient NH4 + to completely displace all cations and fill all exchange sites in soils with high CEC. The unbuffered 1.0 M NH4Cl saturation solution is recommended for forest soils.

Treatment of Septic Effluent for Fecal Coliform and Nitrogen in Coarse-textured Soils: Use of Soil-only and Sand Filter Systems

Groundwater effluent sample collectors(zero-tension lysimeters) were installed directlybelow the drainfields of three residential onsitetreatment systems in the Clover/Chambers Creek aquiferregion of Pierce County near Tacoma, WA. The use of asplit effluent delivery system from the septic tank,where half the effluent was delivered under pressureto a normal native soil-only filter system and halfwas delivered to a sand filter system, allowed thedirect comparison of the two commonly-utilized septicsystems for treatment levels. Septic tank effluent(from the septic tank) and percolating water (between0.3 and 0.9 m beneath the effluent distributionlines) was collected between May 1991 and April 1994on 30 occasions. Samples were analyzed for fecalcoliform bacteria, nitrate, nitrite, ammonium andtotal reduced (Kjeldahl) nitrogen. Results of thisstudy indicate that the use of sand filters greatlyincreased removal of fecal coliform bacteria and totalnitrogen. Soil-only filter systems had an average of91% removal of fecal coliforms and 47%of total N; whereas sand filter systems had an averageof 99.8% removal of fecal coliforms and 80% of total N.

NITRATE SORPTION IN A VARIABLE-CHARGE FOREST SOIL OF THE PACIFIC NORTHWEST

Despite the general acceptance that soils of the Pacific Northwest (United States) have a high retention capacity for phosphate (PO4−3), and perhaps even sulfate (SO4−2), few studies in the region have investigated the potential of physicochemical mechanisms to retain nitrate (NO3−). The specific objectives of this study were to (i) determine the capacity of different horizons of a mesic, Typic Fulvudand under intensive forest management in southwestern Washington to sorb NO3−, (ii) determine the point of zero net charge for each horizon of this soil, and (iii) relate specific mineralogical characteristics to the physicochemical soil properties. Five soil pits were excavated to a depth of approximately 150 cm, and soil samples were composited by genetic horizon, including A, AB, 2Bw1, and 2Bw2 horizons. Through batch equilibration, NO3− sorption isotherms were created for each horizon and showed an increase in sorption with both depth and increased NO3-N solution concentrations. The point of zero net charge of the two Bw horizons was determined to exist between a pH range of 3.5 to 3.6. Selective dissolution techniques of the mineral soil were used to determine the presence of crystalline and noncrystalline aluminosilicates. Allophane and imogolite contents of the less than the 2-mm mineral soil fraction ranged from 0.6% to 3.0% across all observations, although noncrystalline forms of Fe and Al comprised a majority of the subsurface horizons, and increased with depth. The presence of variable charge soil components on this site, coupled with the acidic soil pH regime associated with the coniferous forest stand, allows for the concentration-dependent sorption of NO3−, which may serve to retain a significant proportion of an otherwise highly mobile form of an essential plant nutrient.