Water Quantity and Quality from a Small Georgia Pasture During 1998-2009: Impact of Drought

Proceedings of the 2011 Georgia Water Resources Conference, April 11, 12, and 13, 2011, Athens, Georgia.The water quality impact of pasture grazing in the Piedmont, which generally occurs under low-input management, is not well studied. Cattle, hydrologic and water quality data were collected from 1999 to 2009 from a rotationally grazed 7.8-ha pasture near Watkinsville Georgia. Grazing occurred during 69 time periods, with 20 to 225 head of cattle grazing 1 to 71 days each period. Mean cattle days (head of cattle x days spent) was 182.4 ha⁻¹ grazing-period⁻¹. Drought occurred with 7 of the 11 years having below average annual rainfall. Runoff events were limited to 20 during 86 months of below average rainfall (deficit period) compared with 54 during 46 months of the non-deficit period. Instrument problems limited sample collection to 43-47 out of possible 67 events from 2000-2009. Across all data, mean event flow weighted concentration (FWC) in mg L⁻¹ was < 1.0 for nitrate-nitrogen (NO₃-N) and ammonium-nitrogen (NH₄- N), 3.7 for total nitrogen (TN), 9.1 for total organic carbon (TOC), 2.0 for ortho-P (PO₄4-P), 2.4 for total P (TP), 0.23 for iron (Fe), and 0.06 for aluminum (Al). Nutrient loads in kg ha⁻¹ event⁻¹ averaged 0.04 for NO₃-N, 0.03 for NH₄-N, 0.19 for TN, 0.54 for TOC, 0.11 for (PO₄4-P, and TP, 0.02 for Fe, and 0.01 for Al. Peak nutrient concentrations and loads occurred during calving season and/or when monthly rainfall was above average. Total load was 3 to 6 times greater from non-deficit than deficit periods. Concentrations of N were well below drinking water standards. Nevertheless observed N and P losses could pose risk of eutrophication because it can be stimulated at low concentrations. Such long-term data are needed to help states set or refine water quality standards.Sponsored by: Georgia Environmental Protection Division U.S. Geological Survey, Georgia Water Science Center U.S. Department of Agriculture, Natural Resources Conservation Service Georgia Institute of Technology, Georgia Water Resources Institute The University of Georgia, Water Resources FacultyThis book was published by Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, Georgia 30602-2152. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Research Institutes Authorization Act of 1990 (P.L. 101-307) or the other conference sponsors

No-till and Curve Numbers – A Closer Look

Proceedings of the 2011 Georgia Water Resources Conference, April 11, 12, and 13, 2011, Athens, Georgia.Since its inception in the 1950s, worldwide adoption and use of the Curve Number (CN) methodology for estimating runoff has highlighted some inconsistencies, limitations and problems. Analysis of curve numbers derived from 34 years of rainfall-runoff data, gathered from a 2.7 ha Georgia Piedmont catchment managed under no-till, showed that the average CN (57) that led to mean runoff estimate matching the mean measured runoff was 16 less than the average of the range of CN values (73) given in standard handbook tables for the catchment. The derived median value of the initial abstraction ratio (λ) was 0.04, compared to 0.2, the standard value. Many researchers recommend 0.05 for λ. Use of standard CN coefficients and values for fields managed in no-till, and possibly other conservation tillage systems, would likely lead to overestimation of runoff.Sponsored by: Georgia Environmental Protection Division U.S. Geological Survey, Georgia Water Science Center U.S. Department of Agriculture, Natural Resources Conservation Service Georgia Institute of Technology, Georgia Water Resources Institute The University of Georgia, Water Resources FacultyThis book was published by Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, Georgia 30602-2152. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Research Institutes Authorization Act of 1990 (P.L. 101-307) or the other conference sponsors

IMPACT OF DEEP RIPPING OF PREVIOUS NO-TILLAGE CROPLAND ON SURFACE SOIL PROPERTIES

ABSTRACT The use of continuous no-tillage cropping raises concern about water and nutrient movement into subsoil due to high soil bulk density. Deep ripping (i.e., paraplowing) might be a conservation strategy to loosen surface and subsoil without excessive incorporation of surface crop residues. We initiated a multi-year study comprised of four water catchments (3.1-6.7 acres each) that had previously been under continuous no-tillage cropping for at least 10 years. Two of the water catchments were paraplowed each autumn, but managed otherwise with conservation tillage, similar to the two remaining water catchments. Soil-surface properties were evaluated dur ing the first and second year of the study. Soil bulk density of the surface (20 cm) was significantly lower under paraplowing (1.37 Mg m ). Surface residue C was not different between tillage systems in either year. There was no difference in the standing stock of total organic C in residue and soil to a depth of 20 cm between tillage systems in either year. We conclude from these early years of the study that annual paraplowing in combination with conservation tillage management had few negative impacts on soilsurface chemical properties and may have improved soil physical conditions to possibly allow greater water utili zation

Delineation of Agricultural Drainage Pipe Patterns Using Ground Penetrating Radar Integrated with a Real-Time Kinematic Global Navigation Satellite System

Better methods are needed for mapping agricultural drainage pipe systems. Prior research on small test plots indicates that ground penetrating radar (GPR) is oftentimes capable of detecting buried drainage pipes; however, the feasibility of employing this geophysical technique in larger field areas has not been adequately evaluated. Ground penetrating radar integrated with a Real-Time Kinematic (RTK) Global Navigation Satellite System (GNSS) may be an effective and efficient means of mapping drain lines within agricultural fields. Therefore, GPR-RTK/GNSS was tested in three agricultural settings; with Site 1 and Site 2 located in Beltsville, MD, USA and Site 3 near Columbus, OH, USA. Soils at the three sites ranged from silty clay loam to loamy sand. A GPR unit with 250 MHz antennas was used to detect drainage pipes, and at Sites 1 and 2, a physical GNSS base station was utilized, while a virtual base station was employed at Site 3. The GPR-RTK/GNSS configurations used in this study delineated a complex rectangular drainage pipe system at Site 1, with one set of drainage pipes oriented southwest-northeast and a second oriented southeast-northwest. At Site 2, a herringbone drain line pattern was outlined, and at Site 3, random drain lines were found. When integrated with RTK/GNSS, spiral or serpentine GPR transects (or spiral/serpentine segments of a GPR transects) were utilized to provide insight on drain line directional trends. Consequently, given suitable field conditions, GPR integrated with RTK/GNSS can be a valuable tool for farmers and drainage contractors needing to map subsurface drainage systems

S1 Raw data -

As plant litter decomposes, its mass exponentially decreases until it reaches a non-zero asymptote. However, decomposition rates vary considerably among litter types as a function of their overall quality (i.e., carbon:nitrogen (C:N) ratio and litter chemistry). We investigated the effects of hairy vetch (HV: Vicia villosa Roth):cereal rye (RYE: Secale cereale L.) biomass proportions with or without broadcasted poultry manure on overall litter quality before and during decomposition. As HV biomass proportions increased from 0 to 100%, the relative susceptibility of HV:RYE mixtures to microbial decomposition increased due to: (i) decrease in the initial C:N ratio (87:1 to 10:1 in 2012 and 67:1 to 9:1 in 2013), (ii) increase in the non-structural labile carbohydrates (33 to 61% across years), and (iii) decrease in the structural holo-cellulose (59 to 33% across years) and lignin (8 to 6% across years) fractions. Broadcasted poultry manure decreased the overall initial quality of HV-dominated litters and increased the overall initial quality of RYE-dominated litters. Across all HV:RYE biomass proportions with or without poultry manure, chemical changes during litter decay were related to proportional mass loss. Therefore, the relative decrease in carbohydrates and the concomitant increase in holo-cellulose and lignin fractions were more pronounced for fast decomposing litter types, i.e., litters dominated by HV rather than RYE. While our results suggest possible convergence of litter C:N ratios, initial differences in litter chemistry neither converged nor diverged. Therefore, we conclude that the initial chemistry of litter before decomposition exerts a strong control on its chemical composition throughout the decay continuum.</div

Changes in carbohydrates, holo-cellulose, and lignin concentrations in the decomposing litters containing cover crop (CC) residues with or without poultry manure as a function of proportional mass loss during decomposition for each hairy vetch (HV):Cereal rye (RYE) biomass proportions.

Vertical bars are ±standard deviations. Parameter estimates of the linear models are presented in Table 4.</p

Changes in litter C:N ratios during decomposition as a function of proportional mass loss for each hairy vetch (HV):Cereal rye (RYE) biomass proportions with or without poultry manure additions.

Changes in litter C:N ratios during decomposition as a function of proportional mass loss for each hairy vetch (HV):Cereal rye (RYE) biomass proportions with or without poultry manure additions.</p