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Nov-Dec 2006
November-December 2006: Volume 61, Number 6
Table of Contents
Features
Research
Comparing ratings of the southern phosphorus indices
D. Osmond, M. Cabrera, S. Feagley, G. Hardee, C. Mitchell, P. Moore, R. Mylavarapu, J. Oldham, J. Stevens, W. Thom, F. Walker, and H. Zhang
Soil carbon content after 55 years of management of a Vertisol in central Texas
K.N. Potter
An approach for using soil surveys to guide the placement of water quality buffers
M.G. Dosskey, M.J. Helmers, and D.E. Eisenhauer
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
Effect of pre-plant tillage systems for potatoes in Prince Edward Island, Canada, on soil properties, weed control and potato yield
D. Holmstrom, W. Arsenault, J. Ivany, J.B. Sanderson, and A.J. Campbell
A. Petersen and B. Vondracek
Adjusted T values for conservation planning in Northwest Himalayas in India
D. Mandal, K.S. Dadhwal, O.P.S. Khola, and B.L. Dhyani
Soil quality under food-processing wastewater irrigation in semi-arid land, northern Spain: Aggregation and organic matter fractions
I. Virto, P. Bescansa, M.J. Imaz, and A. Enrique
Departments
Comparing ratings of the southern phosphorus indices
D. Osmond, M. Cabrera, S. Feagley, G. Hardee, C. Mitchell, P. Moore, R. Mylavarapu, J. Oldham, J. Stevens, W. Thom, F. Walker, and H. Zhang
D.
ABSTRACT: The use of site assessment indices to guide agricultural phosphorus (P) nutrient management has been widely adopted in the United States. This study compares P-index ratings from 12 southern states (Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, New Mexico, North Carolina, Oklahoma, South Carolina, Tennessee, and Texas) on fields representing three dominant southern agricultural systems: upland pasture, upland cornfield, and artificially drained field. The structure of each P-index varied enough to produce widely divergent ratings when applied to similar scenarios where individual factors (such as soil test P, poultry broiler litter application rate, or buffer absence or presence) were adjusted across a broad range of P-index input values. Variation in P-index ratings was the unique combination of each state’s selected factors, weighting of the factors, and factor combination (added, multiplied, or a mixture of both addition and multiplication). Although the flexibility of and differences among the southern states’ P-indices result in dramatically diverse P-index ratings for the same set of conditions, the diversity in P-index construction allows for indices designed to match individual state conditions and concerns. The substantial differences in P-index results identified in this survey highlight the need for close coordination between states in revising P-indices if they are to be applied across state lines.
Keywords: P-index, Southern CSREES region
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Soil carbon content after 55 years of management of a Vertisol in central Texas
K.N. Potter
Abstract: Management’s effects on soil physical properties can be difficult to determine because there is often no fixed starting point. Soil organic carbon was determined for central Texas Vertisols (Udic Pellusterts) on archived samples from 1949 and samples taken in 2004. Management records were used to interpret the data. Five fields were sampled, representing an untilled native pasture, two previously tilled soils which had been planted to Bermuda grass (Cynodon dactylon (L.) Pers.) for 55 and 39 years before the 2004 sampling period, and two fields which had been continuously cropped for nearly the entire 55 year time interval. Soil organic carbon was determined for depth increments of 0 to 15, 15 to 30, 30 to 60, 60 to 90 and 90 to 105 cm (0 to 6, 6 to 12, 12 to 24, 24 to 36 and 36 to 42 in). The tilled soils had been seriously degraded of organic carbon by agricultural activities prior to 1949 compared to the native pasture soil. Soil carbon concentration in croplands had decreased from greater than five percent near the surface of native grasslands to less than one percent in croplands. Agricultural practices since 1949 have increased soil carbon concentration in the surface 15 cm (6 in) to 1.45 percent in croplands and 2.09 percent in restored grasslands. Returning the soils to grass production increased soil surface carbon contents at a faster rate than the conventional agricultural practices. Having archived samples greatly aided in interpreting the effects on management on the soil. It appears that previous estimates of carbon sequestration rates for the Vertisols may have been under estimated by comparative studies of no-till and conventional tillage practices.
Key words: Archived soil samples, management effects, soil organic carbon
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An approach for using soil surveys to guide the placement of water quality buffers
M.G. Dosskey, M.J. Helmers, and D.E. Eisenhauer
Abstract: Vegetative buffers may function better for filtering agricultural runoff in some locations than in others because of intrinsic characteristics of the land on which they are placed. The objective of this study was to develop a method based on soil survey attributes that can be used to compare soil map units for how effectively a buffer installed in them could remove pollutants from crop field runoff. Three separate models were developed. The surface runoff models for sediment and for dissolved pollutants were quantitative, based mainly on slope, soil, and rainfall factors of the Revised Universal Soil Loss Equation (RUSLE), and were calibrated using the Vegetative Filter Strip Model (VFSMOD) for a standard buffer design and field management. The groundwater model categorized map units by the presence or absence of suitably-shallow groundwater and hydric conditions for interaction with the root zone of a buffer. The models were applied to a ~65 km2 (~25 mi2) agricultural watershed in northwestern Missouri. Data acquisition, calculations, and map production utilized the Soil Survey Geographic Database (SSURGO) digital database. For surface runoff, soil survey-based values correlated strongly with corresponding VFSMOD estimates for sediment (R2=0.94) and dissolved pollutant trapping efficiency (R2=0.83) for a wide range of soil, slope, and rainfall conditions. A strong negative correlation between trapping efficiency and field runoff load was indicated. Mapped results revealed large differences in buffer capability for surface runoff across the test watershed (21 to 99 percent for sediment and seven to 47 percent for dissolved pollutants). Trapping efficiency for dissolved pollutants was much smaller than for sediment in every map unit. Lower values of trapping efficiency were associated with map units where runoff loads are higher and where a buffer will trap greater loads of sediment, but smaller loads of dissolved pollutants, than in units with higher values. Comparative rankings can be adjusted somewhat for site conditions that depart from the reference conditions, and recalibration may be desired to better account for them. For groundwater, the confluence of hydric conditions and shallow water table occurred only in the highest reaches of the test watershed, but a buffer can also interact with groundwater in most upland and riparian locations due to the prevalence of a seasonally shallow water table. By this approach, soil surveys may be used as a screening tool to guide planners to locations where buffers are likely to have a greater impact on water quality and away from those where impact is likely to be small.
Keywords: Filter strip, groundwater, models, nonpoint source pollution,
riparian buffer, surface runoff, SSURGO
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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.
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Effect of pre-plant tillage systems for potatoes in Prince Edward Island, Canada, on soil properties, weed control and potato yield
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
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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
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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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Soil quality under food-processing wastewater irrigation in semi-arid land, northern Spain: Aggregation and organic matter fractions
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
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