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Vegetation and soil Quality effects from hydroseed and compost blankets used for erosion control in construction activities
            L.B. Faucette, C.F. Jordan, L. M. Risse, M.L. Cabrera, D.C. Coleman, and L.T. West

ABSTRACT: Soil erosion is one of the biggest contributors to nonpoint source pollution in the United States. Soil loss rates from construction sites are 10 to 20 times that of agricultural lands. The use of surface applied organic amendments has been shown to reduce runoff and erosion through enhanced vegetation growth and soil quality characteristics. The objective of this study was to evaluate the vegetation growth and soil quality effects from compost blanket and hydroseed applications to soils disturbed by construction activities. Four types of compost blankets, two hydroseeded treatments (silt fence and mulch filter berm) and a bare soil (control) were applied in field test plots. Treatments were seeded with common Bermuda grass (Cynodon dactylon). Vegetative growth (percent cover and biomass of weeds and grasses) and soil quality characteristics were evaluated periodically over one year and 18 months, respectively. Results showed compost blankets provided an average of 2.75 times more vegetative cover than hydroseed after three months. After one year, cover was similar, but hydroseed had significantly greater weed biomass than compost and a greater ratio of weed biomass relative to Bermuda grass biomass. One type of compost blanket increased surface soil extractable organic carbon, and another type increased organic matter in 0 to15 cm (0 to 6 in) soil depths relative to hydroseed treated soils. A one-time application of hydroseed that included mineral phosphorus (P) fertilizer elevated surface soil P after 18 months. On construction sites where disturbed soils are prone to erosion and vegetation establishment is required, compost applications will promote quicker vegetation cover with less weed growth than hydroseeding. Some compost erosion control blankets have the ability to increase soil quality characteristics relative to hydroseed applications within 18 months of application. 

Landscape segmentation modeling in agricultural fields: Correlating soil pH to herbicide persistence

            A.M. Smith, G.M. Coen, J.R. Moyer, and R. Dunn

ABSTRACT: There is an increasing recognition that spatial variability in soils occurs across the landscape within a field making differential management practices warranted. Differences in herbicide persistence in the soil can result in variation in crop injury across the landscape. Soil pH, which is also reported to vary across the landscape, influences herbicide persistence. Thus, this study investigates the ability to map and delineate within-field soil pH variability using landscape segmentation analysis and provide a tool for predicting herbicide persistence. The area, comprising a conventional and a no-till field in southern Alberta, was surveyed using a dual frequency global positioning system; a digital elevation model was created and landform segments defined. Four landform segments were effective in delineating soil pH zones that could be related to herbicide persistence. The lower slopes in both fields, with pH < 6.0, showed imidazilinone persistence. Carryover of sulfonylurea and triazine herbicides was evident in the upper slopes of the conventional till field only (pH 7.8!7.9). The results suggest that landscape segmentation modeling could provide a valuable tool in managing field spatial variation in soil.

Keywords: Conventional till, herbicide persistence, landform segment, no-till, spatial variability

            D. Holmstrom, W. Arsenault, J. Ivany, J.B. Sanderson, and A.J. Campbell

ABSTRACT: Prince Edward Island, Canada produces more than 45,000 ha (111,197 ac) of potatoes (Solanum tuberosum L.) mostly in a three-year rotation on sloping land on a fine, sandy loam soil that is prone to soil erosion in the spring and during the growing season. This intensive production system has resulted in problems with soil quality and erosion because much of the land is plowed in the fall. Soil erosion can be reduced by use of conservation tillage, but these practices may negatively impact crop performance. Work was initiated in 1999 at the Harrington Research Farm to determine the effects of four tillage regimes: residue management, zero tillage, zone tillage, and conventional tillage on soil properties, weed control, and yield and quality of Russet Burbank potatoes. The conservation tillage practices of zone tillage, zero tillage, and residue management resulted in reduced soil erosion rates and sediment loss compared to the conventional tillage method. Soil penetration resistance was increased by as much as 1000 kPa with some systems. However, soil penetration resistance did not approach levels that are considered detrimental to root growth (1500 kPa). Early spring soil moisture levels were higher by two to 12 percent with conservation tillage treatments but planting was not delayed compared to commercial producers who used conventional tillage. No effect was found on weed control or potato plant emergence. There was no consistent difference in potato yields with conservation tillage systems used in these studies. Our data suggests that the potential benefits of reduced soil erosion risk and lower producer input costs of conservation tillage systems outweigh the negative effect of higher soil compaction and higher spring soil moisture.

Keywords: Conventional tillage, potato, residue management, soil compaction, soil erosion, soil moisture, zero tillage, zone tillage

Water quality in relation to vegetative buffers around sinkholes in karst terrain

A. Petersen and B. Vondracek

ABSTRACT: There are approximately 8,340 mapped sinkholes in karst terrain of southeast Minnesota. Most sinkholes are adjacent to row crops that likely contribute pollutants to surface waters and aquifers. Vegetated buffers can improve water quality by reducing sediment, fertilizers, pesticides, and other potential contaminants from runoff, and may benefit water quality when placed around sinkholes. We evaluated sediment, nitrogen, phosphorus, and runoff for buffers from 2.5 to 30 m (8.3 to 98 ft) wide with a spreadsheet model. We found buffers 30 m (98 ft) wide may reduce pollution by 80 percent, although buffers 15 m (49 ft) wide may be most cost effective. Buffers could contribute to goals of reducing sediment, nitrogen, and phosphorus loads in Minnesota waters. Buffers 15 m (49 ft) wide around all sinkholes would retire approximately 436 ha (1,077 ac) of land from production and cost approximately $260,000 yr^-1 based on Conservation Reserve Program payments, while requiring <14 percent of the budget of the program for groundwater protection in southeast Minnesota.

Keywords: Filter strips, nitrogen, phosphorus, pollutants, runoff, sediment

Adjusted T Values for Conservation planning in Northwest Himalayas of India
            D. Mandal, K.S. Dadhwal, O.P.S. Khola, and B.L. Dhyani
 

ABSTRACT: Tolerable soil loss (T) is defined as the maximum rate of annual soil erosion that economically and indefinitely will continue to sustain a high level of crop productivity. Currently a T value is assigned to a soil based on its current functional state and structural integrity. However, in India a default T value of 11.2 Mg ha^-1 yr^-1 (5.0 t ac^-1 yr^-1) is being followed. Our objective is to provide adjusted T values for India’s Northwest Himalayan region by incorporating bulk density, water stable aggregate measurements, infiltration rate, soil carbon, and fertility status into the assessment. A quantitative model was used to sum up overall soil performance to define the current state of soil resource. Scaling functions were used to convert soil parameters to a 0 to 1 scale. The normalized values were then multiplied by appropriate weighting factors based on relative importance and sensitivity analysis of each indicator. A categorical ranking of soil 1, 2, or 3 was given to a soil group based on the overall assessment. A general guideline developed by the USDA-Natural Resources Conservation Service (NRCS) was followed to calculate soil loss tolerance for each soil group using effective soil depth. Adjusted T values for the area ranged between 5.0 and 12.5 Mg ha^-1 yr^-1 (2.2 and 5.6 t ac^-1 yr^-1) compared to 11.2 Mg ha^-1 yr^-1 (5.0 t ac^-1 yr^-1). Use of the adjusted T values will improve conservation planning, help meet erosion control regulations for development of sustainable farm operations, and improve watershed management in this portion of India.

Keywords: Erosion control regulation (ECR), erosion tolerance, quantitative approach, soil grouping, T value

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            I. Virto, P. Bescansa, M.J. Imaz, and A. Enrique

ABSTRACT: The use of cannery wastewater for irrigation represents a prime solution in the optimization of water resources in semi-arid areas. However, the environmental risks associated to this practice must be evaluated in detail. Soil quality could be affected as a result of the addition of organic residues and some salts and electrolytes to the soil. We evaluated soil aggregation status and organic matter dynamics in three semi-arid agricultural soils in northeast Spain before and after four years of irrigation trials in order to asses the effect of wastewater irrigation on soil physical status. Aggregation indexes (mean weight diameter, dispersible clay, particulate organic matter abundance, fine sand-size organic matter and carbon (C) linked to the mineral fraction were used as soil quality indicators and quantified before and after four years of trials. Four irrigation treatments (‘clean’ control, two blends of waste and wastewater, and waste water) were applied to three different sites to supply crop water needs. The water application methods, crops and land management varied between sites. A permanent alfalfa crop was planted under sprinkler irrigation on a Xeric Petrocalcid and a Xeric Haplogypsid. A crop rotation (corn, wheat, barley, sunflower) was implemented under flooding irrigation on a Typic Xerofluvent. We speculated that aggregation could be improved as a consequence of the addition of fresh organic residues. However, the simultaneous addition of dissolved salts could counteract for this effect and in fact led to a destabilization of soil structure. Results differed for different soil characteristics (particle-size distribution, gypsum content) and management regimes. Changes in aggregation and/or organic matter fractions were observed in the non-gypsic soils. These changes were due to soil management and properties and were not affected by the application of wastewater. The addition of organic solids in suspension led to a proportionate increase in labile organic matter in the gypsic soil. This had no effect on soil aggregate stability, which was mostly dominated by soluble calcium. Our study illustrates the absence of negative effects of irrigation with cannery wastewater on soil physical status and organic fractions in any of the three studied semi-arid Mediterranean soils.

Keywords: Aggregation, canning industry, organic matter, soil quality, wastewater irrigation