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Sept-Oct 2006
September-October 2006: Volume 61, Number 5
Table of Contents
Features
Taking Nutrient Loads
Can Environmental taxes help manage nutrient loads?
by: Sandra Hoffman, James Boyd, and Eleanor McCormick
A future for Soil Science:
A frank discussion on the discipline of soil science, and the trend toward a profound crisis
By: Philippe Baveye
Research
Tracking farmland conversion and fragmentation using tax parcel data
C.D. Clark, W. Park, and J. Howell
Prioritizing farmland preservation cost-effectively for multiple objectives
E.A. Machado, D.M. Stoms, F.W. Davis, and J. Kreitler
Combining management practices to reduce sediment, nutrients, and herbicides in runoff
M.B. Zeimen, K.A. Janssen, D.W. Sweeney, G.M. Pierzynski, K.R. Mankin, D.L. Devlin, D.L. Regehr, M.R. Langemeier, and K.A. McVay
Compost effect on water retention and native plant establishment on a construction embankment
J.W. Singer, R.W. Malone, M.D. Tomer, T.G. Meade, and J. Welch
Riparian buffer width and nitrate removal in a lagoon-effluent irrigated agricultural area
T.A. Smith, D.L. Osmond, and J.W. Gilliam
Monitoring and predicting manure application rates using precision conservation technology
P.E. Cabot, F.J. Pierce, P. Nowak, and K.G. Karthikeyan
Evaluation of the effectiveness of vegetative filter strips for phosphorus removal with the use of a tracer
Y.J. Kim, L.D. Geohring, J.H. Jeon, A.S. Collick, S.K. Giri, and T.S. Steenhuis
Application of phosphorus sorbing materials to streamside cattle loafing areas
C.J. Penn and R.B. Bryant
Departments
Tracking Farmland conversion and fragmentation using tax parcel data
C.D. Clark, W. Park, and J. Howell
ABSTRACT: Analyses of farmland conversion typically rely on data that has been aggregated to a county level. However, the pattern of farmland conversion at the individual parcel level could have important implications for the sustainability of agricultural operations within a limited geographic area. This paper uses data on farm parcels that have withdrawn from Tennessee’s differential assessment program to track farmland conversion at the individual tax parcel level for a single east Tennessee county. The pattern and pace of farmland conversion is described over an 18-year period and a metric from the habitat fragmentation literature—edge density—is used to quantify the extent to which this conversion has increased the fragmentation of the county’s remaining agricultural lands. Edge density, as used in this paper, provides a relative measure of the extent of the interface between agriculture and other land uses. The results suggest that agricultural lands became more fragmented every year for which data was available, although the extent of this increase varied substantially from one year to the next. More specifically, while conversion to residential use increased fragmentation, conversion to both commercial and industrial uses tended to decrease fragmentation. The data and methodologies employed in this paper, although relatively new to the farmland conversion literature, could prove to be valuable tools in analyzing the conversion of agricultural lands and in designing policies to ameliorate the adverse effects of such conversion.
Keywords: Differential use taxation, farmland conversion, fragmentation, land use change
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Prioritizing farmland preservation cost-effectively for multiple objectives
E.A. Machado, D.M. Stoms, F.W. Davis, and J. Kreitler
ABSTRACT: American society derives many benefits from farmland and is often willing to pay to preserve it from urbanization. We present an innovative framework to support farmland preservation programs in prioritizing conservation investments. The framework considers the full range of social benefits of farmland and improves the application of decision analysis methods to the process. Key factors for ranking farms are: 1) social objectives and priorities 2) how much farmland value is expected to be lost to development if not preserved, 3) how much farmland value is already secured in the agricultural region, and 4) how much it will cost to secure the farm’s benefits. The framework can be applied strategically over an entire region or to rank a set of applications from landowners. We demonstrate our framework using three criteria in the Bay Area/Delta bioregion of California, USA.
Keywords: Amenities, conservation planning, decision analysis, ecosystem services, farmland preservation, GIS, public preferences, urban growth management, social value
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Combining management practices to reduce sediment, nutrients, and herbicides in runoff
M.B. Zeimen, K.A. Janssen, D.W. Sweeney, G.M. Pierzynski, K.R. Mankin, D.L. Devlin, D.L. Regehr, M.R. Langemeier, and K.A. McVay
ABSTRACT: Best management practices have been recommended for controlling nutrient, herbicide, or sediment losses with surface runoff. This study was designed to determine the best overall combination of tillage and application practices to reduce surface losses from cropland. Runoff was collected from two Kansas sites in sorghum-soybean rotation during the 2001 to 2004 crop years and analyzed for bioavailable P, soluble P, total P, ammonium, nitrate, total N, sediment, atrazine, and metolachlor concentrations. No-till (NT) treatments consistently experienced higher runoff water volumes than the chisel/disk (CH) tillage system used to warm and dry these clay soils in the spring. For this reason the NT treatments also had higher nutrient and herbicide losses than CH regardless of use of high (H) or low (L) application management techniques. The H included fertilizer and herbicide application practices intended to reduce losses with runoff while L broadcast applied fertilizer and herbicide at planting. Few consistent differences were seen for pollutant loss between the H and L management. When average losses for all eight location-years were compared to CHL, soluble P losses were 3.0 and 2.1 times higher for NTL and NTH, respectively; metolachlor losses were 2.4 and 2.7 times higher for NTL and NTH, respectively; and atrazine losses were 4.8 and 6.1 times higher for NTL and NTH, respectively. The CHL did experience two times higher sediment losses compared with the NTL or NTH, when averaging over all eight location-years. However, tolerable soil loss was not exceeded. CHL generally had small losses for all tested pollutants and may be the best management combination to simultaneously reduce nutrient, herbicide, and sediment losses with cropland runoff for sites like those used in this study.
Keywords: Claypan, integrated management, surface runoff, tillage, water quality
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Compost effect on water retention and native plant establishment on a construction embankment
J.W. Singer, R.W. Malone, M.D. Tomer, T.G. Meade, and J. Welch
ABSTRACT: Compost amendment of soil provides benefits that are well documented for agricultural soils, but not for disturbed soils in urban environments. The objective of this study was to determine if yard-waste compost increased soil moisture and native plant establishment along a construction embankment (cut slope with mean of six percent) in Altoona, Iowa. Compost was surface applied or incorporated at the beginning of the study period at a rate of 143.1 Mg dry matter ha-1 and compared to a control that received no compost. Plant community composition shifted during the three-year study period from annual grass- (primarily foxtail, Setaria sp.) and forb-dominated communities to perennial communities. After three years, species composition was similar, although species density was greater in compost treatments compared to the control at the upper slope (10.9 vs. 6.3 species m-2). Shoot biomass was greater in compost treatments compared to the control (395 vs. 154 g m-2). Following significant rainfall (greater than 2 cm or 0.79 in), water storage (0 to15 cm; 0 to 6 in depth) was greatest when compost was incorporated (5.7 cm; 2.2 in), but surface application also resulted in greater moisture (5.4 cm; 2.1 in) than the control (5.0 cm; 2 in). While treatment effects on soil moisture (p less than 0.05) occurred following rain, slope-position effects only occurred under dry conditions. Surface applying or incorporating yard-waste compost to construction embankments can increase water retention after rainfall and increase plant growth.
Keywords: Native plants, slope position, yard-waste compost, water content
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Riparian Buffer width and nitrate removal in a logoon-effluent irrigated agricultural area
T.A. Smith, D.L. Osmond, and J.W. Gilliam
ABSTRACT: The ideal buffer width required to maximize water quality benefits while minimizing unnecessary land utilization is difficult to determine. This study examined the effect of increasing buffer width on nitrate (NO3-N) reduction in shallow groundwater in the Middle Coastal Plain of North Carolina. The study site was a streamside buffer zone where previous research determined the buffer did not sufficiently reduce NO3-N discharge to stream water. Buffer width was increased from 9 to 30 m (30 to 98 ft) by fencing out cattle and allowing volunteer vegetation to emerge, thus forming a grass and shrub buffer along the newly widened area. Buffer functions were assessed by comparing groundwater NO3-N concentrations from this new system with the same area prior to widening. A significant increase in percent NO3-N reduction was observed in shallow (0.8 to 1.2 m; 2.6 to 4.0 ft) groundwater on the east (34.7 percent to 95.0 percent; p=0.02) side of stream, most likely due to an increase (p=0.01) in DOC at this depth. Reduction at the 30-m width in shallow groundwater at the west side of stream was measured at 93.3 percent, although this was not a statistically significant increase from the 9-m width (53.1 percent; p=0.2). Percent NO3-N reduction was less efficient in deep (2.4 to 4.5 m; 7.9 to 14.5 ft) groundwater, although a significant increase (-37.8 percent to 39.2 percent; p=0.003) at the east side of stream was observed. Reduction on the west side at this depth significantly decreased (19.5 percent to –5.1 percent; p=0.05) suggesting that the deeper confining layer along this side of stream allowed groundwater to bypass the zone of high DOC enhanced by riparian vegetation, thus minimizing the effects of buffer widening in this area. Stream sampling indicated no significant difference in upstream and downstream NO3-N between the two buffer widths (p=0.61). Although increasing the buffer width did improve reduction in some areas, the severity of the groundwater NO3-N situation at this site was not completely resolved by increasing the buffer width to 30 m.
Keywords: Groundwater, nitrate-nitrogen, riparian buffer, water quality
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Monitoring and predicting manure application rates using precision conservation technology
P.E. Cabot, F.J. Pierce, P. Nowak, and K.G. Karthikeyan
Abstract: A side-discharge manure spreader was retrofitted with precision conservation technology. Lateral patterns and swath widths remained relatively constant with peaks in lateral application rates (kg ha-1) at 4 to 6 m (13 to 20 ft) (liquid manure) and at 2 to 7 m (7 to 23 ft) and 20 to 25 m (66 to 82 ft) (solid manure) from the spreader. A “dump zone” of thicker manure application occurred for the initial 0 to 6 m of travel (liquid manure). The minimum scale of precision that can be achieved realistically with this type of equipment depends on the swath width. Results suggest that nitrogen (N) is less manageable than soil phosphorus levels and organic matter by simply retrofitting side-discharge spreaders with precision technology. Lateral pattern of measured application rate was fitted to a three-parameter function using the gamma (?) distribution. Regression of measured liquid manure application rates samples against predicted rates was significant (R2 > 0.80; p < 0.01). The average accuracy of predicted values was ±10 percent, excluding one outlier.
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Evaluation of the effectiveness of vegetative filter strips for phosphorus removal with the use of a tracer
Y.J. Kim, L.D. Geohring, J.H. Jeon, A.S. Collick, S.K. Giri, and T.S. Steenhuis
ABSTRACT: Vegetative filter strips are commonly used as a best management practices to control agricultural pollution. This study investigated the relationship between flow pattern and removal of dissolved phosphorus (P) within vegetative filter strips treating milk house wastewater on two dairy farms located in the Catskills/Delaware watersheds, which are the source of drinking water for New York. Numerous surface and subsurface wells were monitored in the two vegetative filter strips, and chloride tracer was applied to evaluate flow paths. Soluble reactive P concentrations were measured during regular milk house wastewater discharges prior to and during chloride application. Chloride breakthrough showed wastewater flowing preferentially through the vegetative filter strip. The soluble reactive P concentrations were significantly higher within the preferential flow paths compared to the other less saturated parts of the vegetative filter strip. Removal of soluble reactive P was minimal in a saturated flow path, which persisted for 15 m (6 in) and only began to occur as the wastewater eventually dissipated into drier soil areas. Although soluble reactive P concentrations were eventually reduced to below 0.2 mg L-1 at the bottom of both vegetative filter strips, these results suggest the importance of proper design, site and location characteristics, and maintenance to assure uniform distribution and infiltration of wastewater within the vegetative filter strip to maintain effectiveness and prolong the life of the vegetative filter strip.
Keywords: Best management practices, milk house wastewater, phosphorus, preferential flow, vegetative filter strip
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Application of phosphorus sorbing materials to streamside cattle loafing areas
C.J. Penn and R.B. Bryant
ABSTRACT: Excessive soil phosphorus (P) concentrations among cattle loafing areas located in close proximity to surface waters represent great potential for P transport. This study assessed the ability of several P sorbing materials in reducing P losses from streamside cattle loafing areas. Simulated rainfall was applied at seven (time 1) and 28 (time 2) days after P sorbing material applications to runoff plots on cattle loafing areas located at Amish farms. Treatments consisted of alum, water treatment residuals, fly-ash, gypsum, and no amendment (control). Alum addition reduced time 1 runoff P concentrations the most followed by water treatment residuals ~ gypsum, then fly-ash. However, runoff P losses from P sorbing materials were not significantly different from the control at time 2. These results suggest that P sorbing materials alone provide only a temporary solution to P losses from cattle loafing areas and should be used with other best management practices.
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ABSTRACT: Streambank restoration projects utilize large black willow (Salix nigra) cuttings otherwise known as posts; however, potential exists that smaller size cuttings alone or in combination may improve success efforts. Furthermore, the effects of soil moisture conditions and the potential interaction between size of the cutting and soil moisture regime have not been tested. Therefore, a greenhouse study was conducted to quantify cutting performance in response to the combined effects of soil moisture and diameter size. Replicated cuttings with basal diameters measuring 1, 5, or 10 cm (0.4, 2, or 4 in) were placed in three soil moisture regimes including well-watered, periodic flooding and drought. Biomass accumulation and partitioning, height, and survival were measured. Under periodic flooded conditions, 10 cm (4 in) cuttings had greater leaf number and weight (p<.05), leaf area index (p<.05), shoot weight (p<.05), root weight (p<.05), and height growth (p<.05) compared to 1 and 5 cm (0.4 and 2 in) cuttings (p<.05). Survival was best for 1 cm (0.4) cuttings in all three moisture regimes (100 percent) and for 10 cm (4 in) cuttings under flooded conditions (100 percent). Growth and biomass of 10 cm (4 in) cuttings were reduced by drought compared to periodic flooding treatment (p=.02). Based on the data, it appears that planting strategies using 1 cm (0.4 in) cuttings of black willow in any given moisture regime may lead to increased survival rates. Planting larger cuttings may improve overall restoration success. The technique of planting a combination of these two diameters may help to further stabilize streambanks.
Keywords: Cutting size, erosion control, riparian restoration, streambank stabilization, soil moisture
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