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Treatment Plots (treatment + plot)

Distribution by Scientific Domains

Life Sciences	80%

Selected Abstracts

CONTROLLING PHOSPHORUS IN RUNOFF FROM LONG TERM DAIRY WASTE APPLICATION FIELDS,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2004
Anne M.S. McFarland
ABSTRACT: Phosphorus (P) in runoff from long term animal waste application fields can contribute to accelerated eutrophication of surface waters. Manure when applied at nitrogen (N) agronomic rates generally increases soil P concentrations, which can increase runoff of soluble P. Along the North Bosque River in central Texas, dairy waste application fields are identified as the most controllable nonpoint source of soluble P in a total maximum daily load. To evaluate P reduction practices for fields high in soil extractable P, edge-of-field runoff was measured from paired plots of Coastal bermudagrass (Cynodon dactylon) and sorghum (Sorghum bicolor)/ winter wheat (Triticum spp.). Plots (about 0.4 ha) received manure at P agronomic rates following Texas permit guidelines and commercial N during the pretreatment period. During the post-treatment period, control plots continued to receive manure at P agronomic rates and commercial N. Treatment plots received only commercial N during the post-treatment period. Use of only commercial N on soils with high extractable P levels significantly decreased P loadings in edge-of-field runoff by at least 40 percent, but runoff concentrations sometimes increased. No notable changes in extractable soil P concentrations were observed after five years of monitoring due to drought conditions limiting forage uptake and removal. [source]

Revegetation of Pb/Zn Mine Tailings, Guangdong Province, China

RESTORATION ECOLOGY, Issue 1 2000
Z. H. Ye
The Lechang lead/zinc mine is located in the north part of Guangdong Province, southern China. The tailings residue from the extraction of lead/zinc ores was permanently stored in tailings ponds, which required revegetation to reduce the environmental impact. A field study was, therefore, conducted to evaluate the effects of different ameliorants, including: (1) pig manure (PM); (2) mushroom compost (MC); (3) burnt coal residue (BC); (4) fly ash (FA); and (5) surface soil on the growth of Agropyron elongatum (tall wheat grass), Cynodon dactylon (Bermuda grass), Lolium multiflorum (Italian ryegrass), and Trifolium repens (clover) in the tailings residue. The results from the core profiles indicated that adding FA (10 cm) or BC (15 cm) as a barrier layer between the cover soil and the tailings could increase pH, compared to the treatment with soil only. C. dactylon grew well and had a high cover (90,100%) in all the treatment plots except the control plots without any amendment. A. elongatum and L. multiflorum had a higher cover when grown in plots covered with a barrier layer using FA or BC (both with surface soil), than those grown in plots covered with surface soil only. Treatment plots receiving a thicker soil cover (30 cm) had a better dry weight yield than those with a thinner soil cover (15 cm), regardless of the barrier layer. The results from this study indicate that the use of either 15 cm BC or 10 cm FA as a barrier layer with surface soil, or the use of 38 tonnes PM/ha and 6 cm MC, were effective for the revegetation of Pb/Zn mine tailings. C. dactylon was the best species among the four species used for revegetation. Key words: reclamation, Pb/Zn mine tailings, burnt coal, mushroom compost, fly ash, Bermuda grass, Italian ryegrass, clover. [source]

The sensitivity of annual grassland carbon cycling to the quantity and timing of rainfall

GLOBAL CHANGE BIOLOGY, Issue 6 2008
WENDY W. CHOU
Abstract Global climate models predict significant changes to the rainfall regimes of the grassland biome, where C cycling is particularly sensitive to the amount and timing of precipitation. We explored the effects of both natural interannual rainfall variability and experimental rainfall additions on net C storage and loss in annual grasslands. Soil respiration and net primary productivity (NPP) were measured in treatment and control plots over four growing seasons (water years, or WYs) that varied in wet-season length and the quantity of rainfall. In treatment plots, we increased total rainfall by 50% above ambient levels and simulated one early- and one late-season storm. The early- and late-season rain events significantly increased soil respiration for 2,4 weeks after wetting, while augmentation of wet-season rainfall had no significant effect. Interannual variability in precipitation had large and significant effects on C cycling. We observed a significant positive relationship between annual rainfall and aboveground NPP across the study (P=0.01, r2=0.69). Changes in the seasonal timing of rainfall significantly affected soil respiration. Abundant rainfall late in the wet season in WY 2004, a year with average total rainfall, led to greater net ecosystem C losses due to a ,50% increase in soil respiration relative to other years. Our results suggest that C cycling in annual grasslands will be less sensitive to changes in rainfall quantity and more affected by altered seasonal timing of rainfall, with a longer or later wet season resulting in significant C losses from annual grasslands. [source]

Sawdust Addition Reduces the Productivity of Nitrogen-Enriched Mountain Grasslands

RESTORATION ECOLOGY, Issue 6 2009
T. Spiegelberger
Abstract Anthropogenic nutrient enrichment of mountain grasslands has boosted grasses and fast-growing unpalatable plants at the expense of slow-growing species, resulting in a significant loss in biodiversity. A potential tool to reduce nutrient availability and aboveground productivity without destroying the perennial vegetation is carbon (C) addition. However, little is known about its suitability under severe climatic conditions. Here, we report the results of a 3-year field study assessing the effects of sawdust addition on soil nutrients, aboveground productivity, and vegetational composition of 10 grazed and ungrazed mountain grasslands. Of particular interest was the effect of C addition on grasses and on the tall unpalatable weed Veratrum album. After 3 years, soil pH, ammonium, and plant-available phosphorus were not altered by sawdust application, and nitrate concentrations were marginally higher in treatment plots. However, the biomass of grasses and forbs (without V. album) was 20,25% lower in sawdust-amended plots, whereas the biomass of V. album was marginally higher. Sawdust addition reduced the cover of grasses but did not affect evenness, vegetation diversity, or plant species richness, although species richness generally increased with decreasing biomass at our sites. Our results suggest that sawdust addition is a potent tool to reduce within a relatively short time the aboveground productivity and grass cover in both grazed and ungrazed mountain grasslands as long as they are not dominated by tall unpalatable weeds. The technique has the advantage that it preserves the topsoil and the perennial soil seed bank. [source]