Progress 03/01/99 to 12/31/03
Outputs
Under this project: 1) changes in soil biological and chemical properties due to no-tillage versus conventional tillage in cotton or type of cover crop were quantified; 2) effect of land conversion from forest to row crops on sediment deposition was measured; 3) effect of broadcast poultry litter on pasture and forest soil quality / productivity and runoff water quality was assessed; 4) potential benefits of alternative management strategies for soil phosphorus (P) where poultry litter is applied were examined; and 5) water quality monitoring studies with rice and row crops were initiated. Studies (1) found increased microbial activity and populations of soil invertebrates under no-till. Cover crop type also affected soil biological parameters. Soil organic carbon (C) was increased by no-till. However, tillage and cover crop effects were generally limited to the upper 3 cm of soil. Regardless, mobility of fluometuron in soil cores was slower no-till soil. Also,
degradation of fluometuron and pendimethalin was faster in no-till soil. However, crop residue on no-till soil affects herbicide fate, particularly for strongly adsorbed compounds. Study (2) found > 1 m sedimentation in a lake results from deforestation 30 years earlier. The AnnAGNPS water quality model was calibrated using recent sediment depth, and used to show greatly reduced sedimentation had best management practices (BMPs) been used from the outset. Studies (3) demonstrated the benefit of poultry litter on bermudagrass yield and increased pine growth. Litter increased the chemical fertility of pasture and forest soils; however, build-up of P was excessive where applied for six years at rates of 10+ Mg / ha. Losses of P in runoff generally paralleled concentration of soil P. Highest losses followed annual litter application. Without freshly applied litter, P runoff could be reasonably well predicted using a short column miscible displacement technique. Across a range of soils
with different levels of soil P, predictions were superior to those obtained using any of several standard measures of soil P. Movement of P within the soil (soil cores from treament plots or in lab column studies) was limited by sorption. High organic C in sandy loam soil with a history of heavy litter application did not affect how quickly reducing conditions (low Eh) developed nor did low Ehs speed movement of P. Studies (4) showed hay harvest (bermudagrass + winter ryegrass) can reduce surface soil P by about 50 mg / kg of soil per year and, thus, may be used to remediate high P soil. Because Louisiana coastal plain soils vary in P sorptin capacity, expected P sorption may serve as a basis for spatially variable litter application, within a soil and between soil types. Also, diet modification (phytase added and P supplement reduced) reduces total P in litter. But, the effect of diet modification on loss of bioavavailable P does not parallel total P content of litter. Tentative
data from study (5) suggest that in-field BMPs with rice in So. Louisiana may be adequate to reduce losses of oxygen-depleting substances and restore water quality to target standards.
Impacts
Where water quality problems are attributed to agriculture, implementation of BMPs is presumed the solution. However, there are often little direct or indirect data on the effectiveness of BMPs. No-tillage and cover crops with cotton improve the quality of alluvial and loessial soils. Potential off-site transport of certain herbicides is less under no-till, helping preserve water quality with respect to these herbicides. While, hindsight suggests long-term use of BMPs may have averted the hard-to-fix problem of lake sediment build-up, other problems may yet be overcome by implementing BMPs. For example, in-field BMPs with rice appear to improve the quality of surface water impacted by suspended sediment and nutrients. Because poultry litter is a rich organic fertilizer, it may improve soil quality and fertility. This appears true for coastal plain pasture and forest soil. Positive response of pine, together with much greater acreage in forest than pasture, make forest
fertilization with poultry litter a promising disposal option. Mobility of P in coastal plain soils, even under low Eh conditions presumably conducive to its movement, appears limited. But, surface runoff losses may be appreciable, especially following application of litter. Management tools such as specialized tests (miscible displacement technique) or management practices such as accounting for the spatial variability of P sorption when planning litter applications, modifying poultry diets and lowering soil P by plant harvest may aid environmentally sound litter management.
Publications
- Gaston, L.A. 2003. Tillage and cover crop effects on herbicide degradation. Louisiana Agriculture. Vol. 46(2):29.
- Gaston, L.A., D.J. Boquet, and M.A. Bosch. 2003. Fluometuron sorption and degradation in cores of silt loam soil from different tillage and cover crop systems. Soil Sci. Soc. Am. J. 67:747-755.
- Gaston, L.A., D.J. Boquet, and M.A. Bosch. 2003. Pendimethalin wash-off from cover crop residues and degradation in a loessial soil. Comm. Soil Sci. Plant Anal. 34:2515-2527.
- Gaston, L., T. Clason and D. Cooper. 2003. Benefits of poultry litter fertilizer on pasture, silvopasture and forest soils. Louisiana Agriculture. Vol. 45(3).
- Gaston, L.A., C.M. Drapcho, S. Tapadar, and J.L. Kovar. 2003. Phosphorus runoff relationships for Louisiana coastal plain soils amended with poultry litter. J. Environ. Qual. 32:1422-1429.
- Gaston, L.A., T.L. Eilers, J.L. Kovar, D. Cooper, and D.L. Robinson. 2003. Greenhouse and field studies on hay harvest to remediate high phosphorus soil. Comm. Soil Sci. Plant Anal. 34:2085-2097.
- Gaston, L.A., J.L. Kovar, and T.J. Sauer. 2003. Predicting phosphorus loss in runoff using a displacement technique. ASA-CSSA-SSA Annual Meetings Abstracts [CD-ROM]. ASA, Madison, WI.
- Foster, A.J., L.A. Gaston, L.L. Southern, and J.L. Shelton. 2003. Phosphorus release from poultry litter under conventional and phytase-amended diets. ASA-CSSA-SSA Annual Meetings Abstracts [CD-ROM]. ASA, Madison, WI.
- Locke, M.A., R.M. Zablotowicz, and L.A. Gaston. 2003. Environmental fate of fluometuron in a Mississippi Delta lake watershed. In Terrestrial field dissipation studies: Purpose, design, and interpretation. E.L. Arthur, C.E. Clay, and A. Barefoot (eds.) ACS Symposium Series.
- McDonald, J.A, L.A. Gaston, S. Jackson, M.L. Locke, and R. Zablotowicz. 2003. Intact soil core method for quantifying pesticide degradation kinetics. ASA-CSSA-SSA Annual Meetings Abstracts [CD-ROM]. ASA, Madison, WI.
- Shelton, J.L., L.L.Southern, and L.A. Gaston. 2003. Evaluation of the nutrient matrix values for phytase in chicks. Southern Poultry Science Society Abstracts.
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Progress 01/01/02 to 12/31/02
Outputs
Earlier research on pesticide fate, phosphorus (P) dynamics, and water quality modeling was continued in 2002. The current pesticide fate study examines effect of matrix geometry on degradation rate. Degradation of BAS 505 is being tracked in homogenous (biometer flasks) and heterogeneous (intact cores) soil. Microbial activity (biomass C) is also monitored. Tentative results suggest that faster dissipation in field studies may partly be due to decreasing microbial activity with time in static systems. P studies included: 1) refinement of a laboratory method for predicting P release in runoff; 2) sub-surface transport; 3) potential for P phytoremediation by hay harvest; and 4) P release from poultry litter. Earlier research showed that P released from short soil columns during miscible displacement was a better predictor of runoff P than any measure of soil P. The earlier apparatus was modified to better control water flux and tested using a finer texture soil than
previously. Results confirmed earlier findings. The effect of soil organic C on P transport in sandy soil was investigated using low and high organic C soils under conditions of aerated and de-aired input P solutions. In all cases, chemically reducing conditions (as measured by Eh) developed in the 5 cm long soil columns. However, this had negligible effect on P mobility, which was generally well-described by Langmuir isotherms determined in separate batch studies. Bermudagrass (Cynodon dactylon L. Pers.) yields and tissue P concentrations from a long-term study showed that four annual hay cuttings could remove about 50 kg P per ha. Data for the first year of winter ryegrass (Lolium multiflorum) in this study showed nearly as much P could be removed by four cuttings of it, thereby doubling potential draw-down of soil P. Reduction of P amendment to poultry feed, coupled with added dietary phytase, may reduce the level of P loading from land-applied poultry litter. A study was
undertaken to determine if diet modification affected the release of bio-available P as well as content of total P. This appeared to be the case using standard methods for manure analysis. However, results from a batch desorption method indicated greater concentration of bio-available P in litter than determined by standard methods. Also, differences due to diet were reduced. A major thrust of project work in 2002 was initiation of field- and sub-watershed-scale studies on the benefits of soil conservation practices for improving water quality. Locations in rice (Oryza sativa) or soybean (Glycine max) production areas have been identified and instrumentation for monitoring runoff volume and water quality begun. Additional locations in the sub-watershed channel are being instrumented. Since fields have levees and specifically located drains, it was possible to delineate all fields so that when included in the AnnAGNPS water quality model, all hydrologic cells contain a single land use
and set of management operations. This situation will make AnnAGNPS calibration / validation easier and lead to better accounting of how much each up-stream cell contributes to total nutrient and sediment load.
Impacts
A better understanding of conservation management effects on biological, chemical and physical properties of Louisiana soils will help refine currently recommended best management practices (BMPs) and may lead to the development of new BMPs. Current pesticide work will help overcome methodological problems that have plagued efforts to determine degradation parameters that are appropriate for field conditions and environmental fate modeling. A major concern regarding land-application of poultry litter is potential loss of P to surface water in runoff and sub-surface flow, where this nutrient may induce eutrophication. This project is developing methodology that will improve our ability to predict off-site transport of P. It is also quantifying a heretofore largely overlooked simple strategy for reducing elevated levels of soil P -phytoremediation, and it is assessing potential environmental benefits of a proposed BMP for poultry waste management -diet modification.
Where practicable, data are being examined with water quality simulation models (e.g., AnnAGNPS) to explore the benefits of different land management scenarios on limiting nutrient and sediment losses from agricultural systems.
Publications
- Gaston, L.A., and M.A. Locke. 2002. Differences in microbial biomass, organic carbon and dye sorption between flow and no-flow regions of unsaturated Dundee soil. J. Environ. Qual. 31:1406-1408.
- Locke, M.A., K.N. Reddy, L.A. Gaston, and R.M. Zablotowicz. 2002. Adjuvant modification of herbicide interactions in aqueous soil suspensions. Soil Sci. 167:444-452.
- Gaston, L., D. Cooper, J. Kovar and P. Bell. 2002. Reducing soil phosphorus by hay harvest. ASA-CSSA-SSA Annual Meetings Abstracts [CD-ROM]. ASA, Madison, WI.
- Mascagni, H.J., L. Gaston and B. Guillory. 2002. Influence of irrigation and rye cover crop on corn yield performance and soil properties. Abstracts LPPA and LAA p. 45.
- Waldron, G., L. Gaston and P. Bell. 2002. Phosphorus transport in a Louisiana coastal plain soil. ASA-CSSA-SSA Annual Meetings Abstracts [CD-ROM]. ASA, Madison, WI.
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Progress 01/01/01 to 12/31/01
Outputs
Studies conducted include research on tillage and cover crop effects on pesticide fate, investigation of a simple model for phosphorus (P) loading into surface runoff from pasture and forest soils, and applications of the AnnAGNPS water quality model. Effects of conventional tillage (CT) and no tillage (NT) and either native vegetation, hairy vetch (Vicia villosa) and wheat (Triticum aestivum) on degradation of pendimethalin and effect of cover crop type on pendimethalin desorption and washoff by simulated rain were examined. Degradation in surface 0 to 3 cm Gigger soil (fine-silty, mixed thermic Typic Fragiudalfs) was generally faster in NT than CT soil, consistent with higher microbial activity in these soils. Within tillage treatments, degradation was faster under native vegetation and wheat cover than under vetch. When fit to first-order degradation, half lives ranged from 47 d (CT vetch) to 17 d (NT native); however, the data were better described by a nonlinear
model for degradation. Low recovery of pendimethalin in washoff from cover crop residues suggests further investigation of the benefits of this herbicide in NT systems is warranted. Potential off-site transport of P from a Ruston soil (fine-loamy, siliceous, thermic Typic Paleudults) supporting bermudagrass (Cynodon dactylon L. Pers.) pasture and loblolly pine (Pinus taeda L.) was examined using triplicate 0.004 ha plots, annually amended with 0, 5, 10 and 20 Mg/ha poultry litter. Concentration of P, as determined by Bray 2, surface 0 to 15 cm soil increased 190, 340 and 790 mg/kg in the 5, 10 and 20 Mg/ha treatments following 6 annual applications of litter. Runoff concentrations of P increased similarly, giving concentrations of dissolved P in runoff 0.8, 3.4 and 4.5 mg / L greater (average pasture and forest), respectively, than in runoff from control plots. Although P in runoff was correlated with surface soil Bray 2 P, water extractable P (as predicted using a mixing cell model
and Langmuir isotherm for P loading into surface runoff) may offer better prediction of potential off-site transport. Preliminary data suggest that inclusion of P release from poultry litter may broaden the applicability of this approach. Water quality simulations using AnnAGNPS demonstrated that surface runoff, nutrient loading, and sediment yield predictions for an artificially delineated farm-scale watershed were essentially identical with those obtained when running the model for the much larger, entire watershed. Thus, implementation of AnnAGNPS for an extracted small-scale region eliminated the processing of extraneous data, reducing simulation time and work. This approach to water quality simulation may allow land managers to conveniently evaluate nutrient and site management plans. Additionally, AnnAGNPS, in conjunction with a sedimentation model, was used to describe accelerated sediment accumulation in a small (2 ha) lake following clearing of the surrounding bottomland
forest 25 years ago. Upland erosion and sediment discharge rates predicted under alternative, conservation management practices indicated that sediment accumulation could have been substantially reduced.
Impacts
A better understanding of conservation management effects on on biological, chemical and physical properties of Louisiana soils will help refine currently recommended best management practices (BMPs) and may lead to development of new BMPs. A major concern regarding use of poultry litter as a fertilizer is potential loss of P in runoff to surface bodies of water. Results from studies with pasture and forest plots amended with poultry litter suggest that the tendency of a soil to release P via simple water extraction may serve as a guide for predicting potential loss into runoff, helping establish a safe upper limit for P loading in surface soil. Water quality simulation models offer the means of examining the benefits of different land management scenarios on limiting sediment and nutrient losses, thus, preserving soil and surface water quality. Adaptation of the AnnAGNPS model to the scale of typical farms is possible without apparent loss of predictive accuracy and,
consequently, may be used by land managers to aid decisions about specific tracts of land.
Publications
- Gaston, L.A., D.J. Boquet, and M.A. Bosch. 2001. Fluometuron wash-off from cover crop residues and fate in a loessial soil. Soil Sci. 166:681-690.
- Gaston, L., D. Boquet, and M. Bosch. 2001. Pendimethalin desorption from cover crop residues and degradation in a loessial soil. In Annual Meetings Abstracts [CD rom] ASA-CSSA-SSA, Madison, WI.
- Judice, W., J. Bettevy, G. Odom, M. Lindsey, and L. Gaston. 2001. Characterization of erosional processes in agricultural fields in Avoyelles Parish, Louisiana. In Annual Meetings Abstracts [CD rom] ASA-CSSA-SSA, Madison, WI.
- Kovar, J.L., L.A. Gaston, C.M. Drapcho, and S. Tapadar. 2001. Relation of soil P to surface runoff P for four soils amended with poultry litter. In Annual Meetings Abstracts [CD rom] ASA-CSSA-SSA, Madison, WI.
- Suir, G., L. Gaston, and A. DeRamus. 2001. Using AnnAGNPS for farm-scale water quality modeling and management. In Annual Meetings Abstracts [CD rom] ASA-CSSA-SSA, Madison, WI.
- Wight, J., L. Gaston, J. Kovar, D. Cooper, L. Robbins, T. Clason, and D. Robinson. 2001. Effects of poultry litter on the quality of a Coastal Plain soil and runoff water. In Annual Meetings Abstracts [CD rom] ASA-CSSA-SSA, Madison, WI.
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Progress 01/01/00 to 12/31/00
Outputs
The scope of this project was broadened to include research on effects of earlier deforestation on soil and water quality (particularly, sediment loading and deposition in downslope surface waters) and effects of poultry litter fertilizer on pasture and forest soil quality and productivity as well as potential nutrient discharge to nearby surface waters. Accelerated deposition of eroded soil in a (formerly) bottomland lake was determined from the distribution of clay, organic matter, anthropogenic Pb and fallout 137Cs. Average annual sediment deposition measured was about 5 cm; however, due to increasing through-flow with increasing deposition, the initial rate was likely greater. The use of these data to help calibrate a water quality model for use with row crop agriculture in this landscape is being explored. Poultry litter fertilizer increases soil organic matter, available nutrients and yields of bermudagrass. Short-term yield response of young pine, however, is
less clear. The downward mobility of P in soil is restricted to the upper 30 cm, even when P-rich poultry litter has been applied at rates as high as 20 Mg / ha. Edge-of-plot concentrations of P in surface runoff parallel application rates of poultry litter, are highest just after litter application and decrease thereafter. Annual loadings of P with continued application of poultry litter lead to increased surface losses. A method that simulates P desorption during infiltration and mixing of runoff and soil water was shown to much more accurately predict concentrations of runoff P than Bray 1, Bray 2, Mehlich 3 or ion exchange resin extraction methods. Significantly greater microbial activity in no-till (NT), rather than conventional-till (CT), soil was confirmed in studies duplicated in the second year of this work. Additionally, significantly higher numbers of earthworms and arthropods were found in the no-till soil. Type of cover crop did not affect microbial activity or earthworm
and arthropod populations. Data on fluometuron degradation in intact cores of a loessal soil were interpreted using reactive transport models developed for these systems. Despite expected greater potential for preferential flow in the NT soil cores, a two-region, mobile / immobile water model offered no better predictions of fluometuron mobility than a homogeneous flow model. Degradation rates obtained from batch degradation studies accurately described fluometuron degradation during intermittent flow through CT and NT native vegetation and wheat soil. However, degradation in cores of the vetch soils was faster than in corresponding batch systems. Loss of mineralized N from the vetch soil cores may have stimulated consumption of fluometuron as a N source.
Impacts
Basic research on soil management practices used to curtail on-site erosion and runoff, and off-site deposition and nutrient enrichment is needed to better understand their underlying mechanisms, and, thereby, identify improvements in best management practices. This project helps establish expected benefits of no-tillage, cover crops and organic amendments for soils of the Lower Mississippi River Valley in Louisiana.
Publications
- Tapadar, S., K.L, Kovar, C.M. Drapcho, and L.A. Gaston. 2000. Soil bioavailable P affects P in surface runoff from soils amended with poultry litter. p. 326. Agronomy Abstracts.
- Gaston, L.A., D.J. Boquet, S.D. Dotch, and M.A. Bosch. 2000. Cotoran wash-off from cover crop residues and degradation in Gigger soil. p. 144-154. In P.K. Bollich (ed.) Proc. 23rd Annual Southern Conservation Tillage Conference for Sustainable Agriculture, Monroe, LA. June 19-21.
- Gaston, L.A., D.J. Boquet, and M.A. Bosch. 2000. Effects of cover crop residue and tillage on fluometuron dissipation in a loessal soil. p. 401. Agronomy Abstracts.
- Lindsey, M.L., L.A. Gaston, J.P. Bettevy, S.M. Bellelo, and J.B. Witty. 2000. Strategies for reducing sediment discharge from agricultural fields in Avoyelles Parish, Louisiana. p. 9. Agronomy Abstracts.
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Progress 01/01/99 to 12/31/99
Outputs
Initial work has focused on quantifying changes in soil biological and chemical properties brought about by conversion to conservation tillage and choice cover crops in cotton production systems. Studies included soil fertility inventory, general microbiological activity, and herbicide dynamics and fate. Progress on these studies is as follows. 1) Samples (0 to 3, 3 to 6 and 6 to 15 cm depths) were collected from two long-term cotton tillage (conventional- or no-) by cover crop (native vegetation, vetch or wheat) by N fertilization rate field-plot experiments on Gigger soil at the Macon Ridge Location of the Northeast Experiment Station in Fall 1998 prior to initiation of the project. A second set of samples were taken in Fall 1999. These have been analyzed for organic matter, pH, exchangeable basic cations and total acidity. The latter two analyses were used to estimate cation exchange capacity (CEC) and fraction base saturation. Results quantified increased CEC
associated with increased organic matter under no-till management. 2) Effects of tillage and cover crop on microbial activity, biomass and soil respiration in Gigger, Commerce and Sharkey soils were investigated. Field experiments on Commerce and Sharkey soils are at the St. Joseph Location of the Northeast Experiment Station. Results of this first year of data showed differences due to tillage and cover crop. Measures of microbial activity in the Gigger soil were consistent with relative fluometuron degradation rates (discussed below). 3) Fluometuron and pendimethalin sorption to (batch) and washoff (rainfall simulator) from native, vetch and wheat residues were determined. HPLC analysis of equilibrium solutions revealed differences in fluometuron adsorption among the cover crops. These results were consistent with relative fluometuron concentrations in through-flow from a series of simulated rains. 4) Effects of the above tillage by cover crop combinations on the rate of fluometuron
and pendimethalin degradation in surface Gigger soil were determined in a batch incubation study. HPLC analysis of soil extracts for fluometuron indicated faster degradation in no-tillage Gigger soil soil and differences due to cover crop, fastest degradation for soil planted with wheat and slowest for soil planted with vetch. 5) Experiments were conducted to quantify the sorption, degradation and mobility of fluometuron and pendimethalin in replicated intact cores of surface Gigger soil corresponding to the above tillage by cover crop treatments. Effluent from soil cores indicated rapid movement of fluometuron but negligible movement of the more highly sorbed pendimethalin.
Impacts
Basic research on conservation practices used to curtail on-site erosion and runoff, and off-site deposition and enrichment is needed to better understand their underlying mechanisms and, thereby, identify improvements in these best management practices and more fully realize their benefits. In particular, there has been very little investigation of the effects of conservation practices on properties of soils in the Delta and Macon Ridge areas of Louisiana
Publications
- No publications reported this period
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