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Tall fescue (Lolium arundinaceum [Schreb.] S.J. Darbysh.) is a widely adopted cool-season perennial forage in the southeastern United States. Historically, tall fescue contained a symbiotic fungal endophyte, Epichloe coenophiala, that produced an ergot alkaloid toxic to livestock. New fescue biotypes have been developed that are endophyte free or include endophytes that produce low-toxicity alkaloids. Ecological implications of these biotypes are not fully understood. We evaluated nutrient runoff quality for three tall fescue biotypes (common, high alkaloid endophyte [wild]; low alkaloid endophyte [novel]; and endophyte free [free]) under two fertilizer sources (broiler litter [BL] and inorganic fertilizer) in grazed systems and a hayed system with inorganic fertilization of endophyte free fescue. The seven treatments were replicated twice on 1 ha paddocks near Watkinsville, Georgia. Grazed paddocks were stocked in September each year with weaned Angus (Bos taurus) heifers (2002 to 2007) and steers (2008 to 2009) at rates of ~3 to 6 head paddock–1 adjusted every 28 days to maintain 1 to 3 Mg ha–1 of available forage. Weather conditions varied from very dry to very wet and allowed 15 grazing periods (50 to 198 days). Tall fescue with novel-endophyte association had lower or equal runoff concentrations and loads for inorganic nitrogen (N), total N (TN), ortho-phosphorus (ortho-P), and total P (TP) than fescue with wild- or free-endophyte association (fescue treatment mean concentrations [mg L–1]

Broiler litter (BL) and flue gas desulfurization gypsum (FGDG), both readily available in the US Southeast, can potentially ameliorate soil constraints adversely affecting agricultural productivity and environmental quality in the region. However, benefits and risks must be evaluated prior to making recommendations to producers. The effectiveness of a combination of FGDG and grass buffer strips (GBS) to reduce edge-of-field nutrient losses from corn (Zea mays L.) production under inorganic (NPK) or organic (BL) fertilization was evaluated on Coastal Plain soils near Tifton, Georgia, from April of 2014 through January of 2017. Nine treatments were randomly established in each of three replications on plots instrumented to collect runoff. This was the first phase of a three-phase study. Treatments consisted of combinations of three fertilizer treatments (NPK, BL, and BL+FGDG) and three GBS treatments (no GBS [–GBS], GBS without FGDG [GBS−FGDG], and GBS with FGDG [GBS+FGDG]). A tenth treatment of NPK+FGDG without GBS was also included. Annual rates for BL and FGDG were 13.45 Mg ha−1 each. The BL rate was based on a high nitrogen (N) demand of corn and would represent a risky scenario for nutrient loss. Runoff and concentrations and loads of nitrate-nitrogen (NO3-N), ammonium-nitrogen (NH4-N), total Kjeldahl nitrogen (TKN), dissolved reactive phosphorus (DRP), and total P (TP) were determined in runoff from 29 storms from May of 2015, through January of 2017. Rainfall partitioned into runoff (percentage runoff) decreased by 50% to 70% under –GBS with BL or BL+FGDG compared with NPK fertilization, and under GBS–FGDG or GBS+FGDG compared with –GBS for NPK and BL fertilization. Under –GBS, concentration of DRP and TP increased by ~160% from BL compared with NPK fertilization, and by 150% for DRP and by 115% for TP from BL+FGDG compared with NPK fertilization. On the other hand, the combined BL+FGDG and GBS+FGDG treatment reduced nutrient concentration by 65% to 80% compared with BL with –GBS (a standard practice), and nutrient load by 40% to 70% compared with NPK with –GBS (another standard practice) or BL with –GBS. Results indicate the potential for FGDG to improve edge-of-field runoff water quality when applied to fields with BL and to edge-of-field GBS. In planned follow-up articles, results will be compared with phase-2 when BL and FGDG rates were reduced by a third and phase-3 when BL application was discontinued.

Cereal rye (Secale cereale) cover crops supply many agroecosystem services in cropping systems including the provision of allelochemicals for weed suppression. Understanding the distinction between root and shoot relative contributions of these allelochemicals (such as phenolic acids) should provide better insight for residue management following termination of a cereal rye cover crop. A field experiment examining root and shoot contributions of phenolic acids to soil was conducted in 2015 at Beltsville, Maryland. Tissue and soil (0–10 cm) phenolic acid concentrations were analyzed over time using liquid chromatography–mass spectrometry. Cereal rye roots were found to be the primary contributor of phenolic acids to soil. Further, soil phenolic acid concentrations were unaffected by tillage or soil depth. Overall, the phenolic acid concentrations of coumaric > vanillic > 4-hydroxybenzoic acid increased in soils during the first 3–7 days after cereal rye termination and then decreased to initial concentrations after 56 days. Our research forms a basis for future allelopathy research. Specifically, there is a need to understand the contribution of roots to phenolic acid release in soils. Building this body of knowledge will improve our ability to employ allelopathy as part of a multi-tactic weed management system.

Highlights.Precision agriculture (PA) applications in irrigation are stymied by lack of decision support systems.Modern PA relies on sensor systems and near real-time feedback for irrigation decision support and control.Sophisticated understanding of biophysics and biological systems now guides site-specific irrigation.The internet of things (IOT) enables new ways to increase yield per unit of water used and nutrient use efficiency. Keywords: Crop water productivity, Decision support system, Internet of things, Remote sensing, SCADA, Soil water content.

Tillage systems and fertilizer sources impact soil health and ecosystem services. Rainfall simulations can be used to evaluate tillage and fertilizer management effects on ecosystem services associated with runoff amount and quality. Fixed rate (FR; 57 mm h−1 for 60 minutes) and variable rate (VR; based on the pattern of the most frequent spring rain) simulations were conducted on corn (Zea mays L.) plots supplied with conventional fertilizer (CF; ammonium nitrate [NH4NO3]) or poultry litter (PL) and managed with conventional tillage (CT) or no-tillage (NT) on a Cecil soil (Ultisol) near Watkinsville, Georgia. Simulations were conducted in separate years (FR in 2004 and VR in 2005). Tillage and tillage × fertilizer interactions had significant effects on total runoff and sediment loss under FR but not VR. Under FR, 55.8% of the simulated rainfall was partitioned into runoff from CT compared with 9.7% from NT. Under VR, 42% to 60% was partitioned into runoff with no difference among treatments. Sediment loss was 11-fold greater from CT compared with NT under FR (919 g versus 82 g). Under VR, sediment loss varied between 755 g and 2,174 g with no difference among treatments. Tillage and tillage × fertilizer interactions had significant effects on total load for ammonium-nitrogen (NH4-N) and nitrate-nitrogen (NO3-N) in both methods and dissolved reactive and total phosphorus (DRP and TP) under VR. Fertilizer source affected loads of NH4-N under VR and NO3-N and TP under both methods. Our results confirm that 12 years of continuous NT on a Cecil soil, representative of much of the Southern Piedmont, is far superior to CT for reducing runoff and sediment loss. Larger and more intense storms predicted in future climate projections warrant greater adoption of reduced tillage systems to counteract potential runoff and sediment losses from CT systems.

Advances in open‐source microcontroller (MC) technologies have created opportunities for development of low‐cost real‐time environmental data collection systems. An inexpensive system based on the ARDUINO‐MC was developed using a gateway‐node architecture enabling us to collect environmental sensor data across climates and soil types. Printed circuit boards and breakout modules made assembly quick and easy. Nodes interfaced with serial digital interface at 1200 Bd time domain reflectometry soil water sensors, which require higher input voltage and use more complex communication than other sensors commonly used with MC‐based data loggers. Maintaining time synchronization between the nodes and gateways was critical to their ability to communicate and limit field traffic. Power consumption and supply issues and the inability to regularly monitor units led to data loss. Incorporating cellular capability to the gateway gave researchers and technicians near real‐time access to data and opened opportunities for their use in automated databases and visualization dashboards. This paper describes the design, testing, and use of the system during its first two field seasons. This system exemplifies how researchers can economically collect environmental data from remote locations by leveraging the potential of microcontrollers in custom data acquisition systems. Arduino sketches and other materials are available at https://github.com/ArduinoSoilH2O.

Advances in environmental and agricultural management are increasingly enabled by unattended data acquisition using internet‐of‐things (IOT) approaches. These approaches combine advanced sensors and wireless data transmission to automatically convey field data to the internet. Users, either human or machine, then can access and act upon the data from nearly anywhere in the world. Particularly in the case of machines automatically acting on the data, robustness, reliability and accuracy of data are crucial to preventing unintended outcomes of machine operations and continued supply of key services. Low‐cost, low‐power, and solar‐powered systems are important to enable market entry of advanced decision support systems based on IOT data acquisition approaches. The polar vortex outbreak of February 2021 in the central United States provided an extreme test of such a node and gateway system for automatic data acquisition and telemetry to the internet over the cellular telephone network. The system, codesigned by USDA‐ARS and Acclima, performed admirably despite air temperatures reaching a minimum of −24 °C, temperatures < 0 °C for 8 d and < −7 °C for 6 d, two snowstorms, and overcast conditions. The six nodes, gateway, and 36 sensors continued to function reliably with a data transmission failure rate of

Flue gas desulfurization gypsum (FGDG) from coal-fired power plants is readily available for agricultural use in many US regions. Broiler litter (BL) provides plant available N, P, and K but can be a source of unwanted As, Cu, and Zn. As a source of Ca and S, FGDG can reduce losses of P and other elements in runoff from BL-amended areas. Rainfall simulation plots (2.0 m) were established on a Piedmont Cecil soil growing 'Coastal' bermudagrass ( L.) for hay. Accumulation and transport of As, Cu, Cd, Cr, Hg, Pb, and Zn were evaluated after annual BL applications (13.5 Mg ha) with four FGDG rates (0, 2.2, 4.5, 9.0 Mg ha) and two FGDG treatments (0 and 9 Mg ha) without BL. Runoff As concentrations were sixfold greater with BL than without ( ≤ 0.01) and were similar to BL with FGDG at 2.2, 4.5 or 9.0 Mg ha ( ≤ 0.10). Runoff concentrations of target elements did not increase where FGDG was applied alone. After three annual applications of FGDG and BL, soil concentrations of As, Cr, Pb, Hg, and Cu were well below levels of environmental concern. Our findings indicate that runoff losses of As from BL application are not reduced with FGDG but support other research indicating no identifiable environmental risks from FGDG beneficial use in agricultural systems.

The effect of cover crop (CC) surface residues on water, carbon, and nitrogen cycling in no-till systems depends in part on the water retention properties of decomposing residues and the extent of decomposition. This study (1) examined the effect of decomposition on residue water retention properties; (2) characterized diurnal variations in residue decomposition rates in response to changes in soil-residue-air environmental conditions; and (3) examined the diurnal relationships between cover crop surface residue decomposition and residue environment (moisture and temperature). Maximum gravimetric water content ( θ g ) and characteristic water release curves were determined for red clover (Trifolium pratense L.) and cereal rye (Secale cereale L.) residues collected at 0, 4, 10, and 16 weeks after termination for red clover, and at 2, 5, and 18 weeks for cereal rye. In addition, residue carbon dioxide (CO2-C) flux, along with soil-residue-air environmental conditions, were measured diurnally for red clover at 4, 10, and 16 weeks after termination, and for cereal rye at 5 weeks after termination. Maximum residue θ g decreased as decomposition progressed. Cover crop residue decomposition also influenced water release curves such that the water retained at any given water potential ( ψ r e s i d u e ) declined with increasing decomposition. These decomposition-associated changes in residue water retention properties were strongly related to residue lignin concentrations. Cover crop surface residue CO2-C flux showed distinct diurnal patterns that were strongly related to ψ r e s i d u e or residue θ g . At a diurnal scale, residue CO2-C flux increased during the nighttime from 18:00 to 06:00 h when residues gain moisture from the atmosphere and soil, and decreased during the daytime from 06:00 to 18:00 h when residues lost moisture via evaporation. Increase in temperature decreased residue CO2-C flux due to moisture limitations. Therefore, CC surface residue decomposition models must address both diurnal changes in ψ r e s i d u e and the changes in water retention properties as residues decompose.

Cereal rye (Secale cereale L.) is widely grown due to its winter hardiness and adaptability to varied soil and environmental conditions. Fall and spring climate and available soil N drive biomass production. However, there is limited empirical information on the effects of these factors on cover crop performance. Farmers need early spring indicators of cereal rye performance to guide management. A 3-yr experiment was initiated to test and model the effects of climate and soil N fertility on cereal rye growth and allometric relationships in Pennsylvania, Maryland, and North Carolina under five-six fall fertilizer rates. We hypothesized that allometric relationships between early spring growth indicators can guide management decisions. Measurements included tillering, biomass, tissue N, and normalized difference vegetation index (NDVI) at Zadoks growth stages (GS) 25, 30, and 60. Nitrogen application increased biomass: maximum average biomass was 2853, 4844, and 9739 kg ha–¹, respectively, at GS25, GS30, and GS60. At GS25, biomass accounted for the greatest amount of model variation and better predicted GS60 biomass than shoot density and NDVI. Variance attributed solely to GS25 and GS30 biomass constituted 38.5 to 65.2% of total model variance. Models accurately predicted biomass and N accumulation 34 to 60% of the time. This study illustrates the difficulty in predicting late season biomass and N content based on early measurements. One extension of this research would be the development of a simple protocol to accurately sample cereal rye biomass at GS25 to estimate potential N accumulation and biomass at GS60.

Soybean and sunflower are summer annuals that can be grown as an alternative to corn and may be particularly useful in organic production systems for forage in addition to their traditional use as protein and/or oil yielding crops. Rapid and low cost methods of analyzing plant forage quality would be helpful for nutrition management of livestock. We developed and validated calibration models using Near-infrared Reflectance Spectroscopic (NIRS) analysis for 27 different forage quality parameters of organically grown sunflower and soybean leaves or reproductive parts. Crops were managed under conventional tillage or no-till with a cover crop of wheat before soybean and rye-crimson clover before sunflower. From a population of 120 samples from both crops, covering multiple sampling dates within the treatments, calibration models were developed utilizing spectral information covering both visible and NIR region of 61 - 85 randomly chosen samples using modified partial least-squares (MPLS) regression with internal cross validation. Within MPLS protocol, we compared nine different math treatments on the quality of the calibration models. The math treatment “2,4,4,1” yielded the best quality models for all but starch and simple sugars (r2 = 0.699 - 0.999; where the 1st digit is the number of the derivative with 0 for raw spectra, 1 for first derivative, and 2 for second derivative, the 2nd digit is the gap over which the derivative is calculated, the 3rd digit is the number of data points in a running average or smoothing, and the 4th digit is the second smoothing). Prediction of an independent validation set of 28-35 samples with these models yielded excellent agreement between the NIRS predicted values and the reference values except for starch (r2 = 0.8260 - 0.9990). The results showed that the same model was able to adequately quantify a particular forage quality of both crops managed under different tillage treatments and at different stages of growth. Thus, these models can be reliably applied in the routine analysis of soybean and sunflower forage quality for the purposes of livestock nutrient management decisions.

Urea is the most widely used N fertilizer due to its high N concentration (46%), cost effectiveness and ease of handling. However, urea is susceptible to loss as N2O, a greenhouse gas and catalyst of stratospheric ozone decline. Polymer-coated fertilizers may be effective in reducing such losses but the appropriate coating thickness for effective field performance is unknown. We prepared urea granules with polyurethane coating (PCU) based on castor oil at 2%–8% by weight. We tested the fertilizer value of these materials for maize (Zea mays L.) and measured field loss of N2O. Maize grain yield and N uptake were similar in treatments fertilized with urea (uncoated) and each of the coated materials. Cumulative N2O–N per unit of grain yield, however, was reduced by 80% with PCU8% compared with uncoated urea. Results indicate that polyurethane-coated urea performs similarly to uncoated urea for maize production while reducing soil N2O emissions up to 60–80%, with an efficiency factor twice as high as that suggested by the Intergovernmental Panel on Climate Change (IPCC) for N fertilizers. Our results indicate that urea with a polyurethane coating of 8% (PCU8%) had the best combined agronomic and environmental performance in a field study.

Soil acidity is a constraint to global soil and food security, yet access to limestone to correct this problem is limited in many parts of the world. Research suggests that animal manures have a liming effect on acidified soils, representing a potential solution. This long-term (15 year) study used a split plot design to evaluate the effect of conventional tillage (CT) vs no-till (NT) (main plot) under conventional (CF) and poultry litter (PL) fertilizer source applications (sub-plots). A succession of three cropping systems consisting of cotton (Gossypium hirsutum L.) with a winter wheat (Triticum aestivum) cover crop, corn (Zea mays) with rye (Secale cereal), and millet (Panicum miliaceum) with rye was implemented. The soil is a Cecil sandy loam (1:1 kaolinitic). Changes in soil pH, soil organic carbon (SOC), and lime buffer capacity (LBC) were compared among the four treatments CTCF, CTPL, NTCF, and NTPL. The CTPL treatment had a 0.6 unit pH increase in the top 15 cm. However, cropping systems had more effect than tillage or fertilizer source on both soil pH and LBC. All treatments resulted in some increase in subsoil pH. Lime buffer capacity remained unchanged at all but the 76–91 cm depth, where all treatments exhibited a decrease ranging from 27 to 43 kg CaCO3 eq ha−1 pH unit−1 year−1. Our results suggest that previously reported liming effect of animal manures should be examined in the context of soil type and cropping system to better understand the true mechanism(s) of soil acidity amelioration.

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.

The curve number (CN) method for estimating direct runoff from a rainfall event is commonly used in hydrologic investigations, but currently accepted CNs for no-till cropping might need revising. We derived CNs from ranked rainfall-runoff data gathered from 1972 to 2010 from a 2.7 ha, zero-order watershed (P1) near Athens, Georgia. The watershed was initially managed under conventional tillage for 2.5 years, followed by double-cropped continuous no-till rotations. During conventional tillage, on average 19% of the rainfall was partitioned into runoff (median 13%). The mean and median CN was 82 and 85, respectively. Least square fitting of CN versus rainfall produced an asymptotic CN of 81 (R 2 = 0.61). In contrast, the mean and median runoff during no-till was 7% and 0.6% of the rainfall, respectively. The mean CN equaled the median CN of 62. The asymptotic CN was 58 (R 2 = 0.78), compared with 72 from standard tables. When estimated using CN of 72, the mean runoff during no-till was 142% greater than the measured mean runoff. These results support the hypothesis that CNs for no-till cropping systems should be smaller than currently accepted values for comparable watersheds in the region. This has implications for hydrologic modeling for water quantity and quality where the use of the CN method is ubiquitous.

Summary Megacopta cribraria (F.) (Hemiptera: Plataspidae) is a newly invasive, exotic pest of soybean (Glycine max [L.] Merr.; Fabales: Fabaceae) in the southeastern United States. In 2013, the exotic egg parasitoid Paratelenomus saccharalis (Dodd) (Hymenoptera: Platygastridae) was discovered parasitizing eggs of this pest in kudzu (Pueraria montana var. lobata [Willd.] Maesen & S. Almeida; Fabales: Fabaceae) and soybean in 3 states in this region of the United States. We evaluated parasitism of M. cribraria egg masses by P. saccharalis in conventional tillage and no-till organic soybean experimental plots in 2013. Density of M. cribraria egg masses was significantly higher in conventional tillage soybean than in no-till soybean in weeks 2 through 5 for the 7 wk period M. cribraria egg masses were detected on soybean. Percentage of parasitism of M. cribraria egg masses by P. saccharalis was significantly higher in conventional tillage soybean (58.4%) than in no-till soybean (44.9%). In general, parasitism...

Gypsum has been shown to reduce runoff on soils prone to crust formation in the southeastern United States. Increased infiltration from gypsum applications could therefore help reduce runoff P and other nutrient losses from application of broiler litter (BL), a nutrient-rich fertilizer. In rainfall simulation experiments in June 2009 and May 2011, runoff and nutrient (N, P, Ca, Mg) losses in runoff were compared among treatments consisting of 0, 2.2, 4.5, and 9.0 Mg ha⁻¹ flue gas desulfurization gypsum (FGDG) combined with 13.5 Mg ha⁻¹ of BL and two control treatments of (0–0) and (9.0–0.0) Mg ha⁻¹ (FGDG-BL). A randomized block design with three replications was set up on a Cecil (Typic Kanhapludult) soil growing Coastal bermudagrass (Cynodon dactylon L.) for hay near Watkinsville, Georgia. Amendments were applied each April from 2009 to 2011. A reduction in runoff of 30% each year from the (9.0–13.5) compared with the (0–0) treatment was not statistically significant. Gypsum was effective in reducing concentration and load in one of the two study years: P and NH₄–N in 2009 (up to 83%) and NO₃–N in 2011 (up to 73%). A combination of factors related to weather extremes, timing of FGDG and BL applications, and their implication on soil and vegetation responses at different landscape positions might have caused the different responses between years. Additional studies focused on isolating the impacts of such factors would be helpful to ascertain the effectiveness of multiyear applications of FGDG as a best management practice to reduce P and other nutrient losses in soils of the southeastern United States.

Sunnhemp (Crotalaria juncea L.) is a tropical legume that could be an important summer cover crop in the southeastern United States, but it has the potential for suppressing both crops and weeds. Allelopathic effects of sunnhemp on weeds, vegetable crops, and cover crops were evaluated in greenhouse and growth chamber experiments. In the greenhouse, ground dried sunnhemp residues (applied mixed with the soil at 1.6% w/w) reduced percent germination of lettuce (Lactuca sativa L.) and smooth pigweed (Amaranthus hybridus L.) to a similar degree as that caused by cereal rye (Secale cereale L. subsp. cereale) residues (applied at 1.5% w/w). The allelopathic activity of sunnhemp was greater in the leaves than in the roots or stems. In growth chamber studies, the mean reduction in germination (relative to the control) caused by sunnhemp leaf aqueous extracts was: bell pepper (100%), tomato (100%), onion (95%), turnip (69%), okra (49%), cowpea (39%), collard (34%), cereal rye (22%), sweet corn (14%), Austrian winter pea (10%), crimson clover (8%), cucumber (2%), and winter wheat (2%). In lettuce, carrot, smooth pigweed, and annual ryegrass, sunnhemp aqueous leaf extract reduced seedling length to a degree similar as that produced by rye aqueous leaf extract. Sicklepod [Senna obtusifolia (L.) H.S. Irwin & Barneby CA] germination was not inhibited by any of the sunnhemp or rye aqueous extracts. In conclusion, sunnhemp reduced the germination percentage and seedling growth of various crop species. The allelochemical activity in sunnhemp was primarily in the leaves and remained active at least 16 d after harvest under dry conditions. Sunnhemp's allelochemical effect may be a useful attribute for weed management in sustainable production systems. However, plant growth in the field in crops such as bell pepper, tomato, onion, and turnip may be impacted as a result of allelopathic activity of sunnhemp residues. Thus, weed management may be more effective when sunnhemp is grown in rotation with crops that tolerate the allelochemicals from sunnhemp, resulting in optimization of the rotation effects.

Poultry (Gallus gallus domesticus L.) litter (PL) is a readily available nutrient source for crop production in the Southeast USA. Long-term PL application may alter availability of N and the effect may be dependent on tillage practice. Tillage [no till (NT) vs. conventional (CT)] and N source (PL vs. commercial fertilizer CF) effects on N availability and plant uptake were evaluated in years 9, 10, and 11 of a long-term cropping systems study at the United States Department of Agriculture, Agricultural Research Service, J. Phil Campbell Sr. Natural Resource Conservation Center, Watkinsville, GA, USA. Mineral N in the top 10 cm, measured in situ, varied each year and was influenced by time, tillage, and N source. In 2003 (year 9), soil mineral N content was greater in CT–CF (100 kg ha−1) than in NT–PL (95 kg ha−1) but in 2004 (year 10) and 2005 (year 11) it was lower in CT–CF (93 and 60 kg ha−1) compared to NT–PL (140 and 71 kg ha−1). Nitrogen mineralization rates were generally greater for PL than for CF treatments with the difference being almost 1 kg ha−1 day−1 in 2003. Mineralization rates were greater for NT–PL compared to CT–CF in 2004 and 2005. Across the three growing seasons, corn (Zea mays L.) aboveground biomass was consistently greater in the NT–PL treatment than in the NT–CF and CT–CF treatments. Correlation between aboveground biomass and N mineralization was greater for PL than for CF (0.75 vs. 0.48). Patterns of N mineralization and total soil mineral N indicated that the distribution of N through the growing season more closely matched corn N demand in PL treatments. Results indicate that improved N availability through the growing season, by combining NT and PL, can result in more profitable corn production in the southeast.

Water-extractable organic matter (WEOM) contains labile organic carbon (C) and nitrogen (N) and is sensitive to soil management. The objective of this study was to determine the quantity and spectral properties of soil WEOM responding to types of nutrient addition and tillage managements. Soil samples were taken from treatments (con- ventional tillage, no-tillage, poultry litter, and NH4NO3 application) of a 10-year experiment in Watkinsville, Georgia, at different times and soil depths. Air-dried soil samples were extracted by deionized water followed by filtration (G0.45 Km), and soluble C and N, absorptivity at 254 nm, and fluorescence excitation/emission matrix in the extract were determined. Results showed that poultry litter application accumulated higher amounts of water-extractable organic C and N than NH4NO3 application. But no significant difference was found between tillage and no-tillage for both water-extractable C and N. Absorptivity at 254 nm decreased during cropping years for conventional tillage and NH4NO3 application, indicating accumulation of aliphatic organic compounds in WEOM, but the fluorescence-measured humification index showed an opposite trend. For no-tillage and poultry litter application treatments, there was no difference in absorptivity over the sampling time. Parallel factor analysis of excitation/emission matrix data showed that WEOM consisted of three fluorophore components: humic-, fulvic-, and tyrosine- like ''compounds,'' and relative distribution of these components differed among treatments and changed over soil depths. The tyrosine-like com- ponent tended to accumulate in the lower sampling depth (915 cm). Overall, the quantity and spectral properties of WEOM responded to the types of nutrient application and tillage practices.

Submersible pressure transducers integrated with data loggers are commonly used to measure stage (water level) and estimate flow rate from established stage-discharge relationships; however, proper data quality assurance is important to reduce uncertainty in resulting estimates. For 2 yr, USDA-ARS researchers in Watkinsville, Georgia, continuously monitored flow rate from a spring using a flume fitted with a pressure transducer and data logger and performed periodic manual flow rate checks. Initially, during a 162-day period in 2003 with 72 comparisons, the automated system underestimated the mean flow rate by approximately 17% due to presumed drift and lack of frequent calibration. After calibrating the transducer to adjust for drift with the data logger program, 66 comparisons during a 349-day period in 2004 showed that the difference in mean flow rate between the manual and automated estimates was < 5%. During 235 days late in the monitoring period, the automated system overestimated the mean flow rate by approximately 29% because of another apparent drift. In a similar set-up at a pond outflow, a drift of 32 mm in transducer output caused underestimation of pond outflow by 27% during a 30-day period. Users should not assume that pressure transducer-based automated water level measurement systems continuously record correct data. Routine verification of transducer output is crucial to avoid inaccurate (and possibly useless) stage and flow rate estimates.

Conservation tillage and judicious use of animal manures as fertilizers can make significant contributions for sustainable food production in the twenty-first century. Identifying and understanding the many interactions occurring within agricultural systems is fundamental for accomplishing this feat. This paper synthesizes 14 years of research results from a study that began in the early 1990s in which researchers from USDA-ARS and the University of Georgia investigated cropping system influences on nutrient management under natural rainfall. Increases in C and N with no-till resulted in improved soil structure that increased infiltration rate and soil water availability. Biological activity as indicated by earthworms was greater with no-till and poultry litter (PL). In all but the very driest year, yields of cotton and corn increased on average 10–27% with no-till and 32–42% with combination of no-till and PL. On the other hand soil nutrient accumulation, particularly P and Zn from long-term use of poultry litter in corn production, reached excessive levels and could present environmental risks. Drainage increased in no-till raising the risk of leaching of nutrients into the soil profile. However, runoff decreased in no-till and the presence of a rye cover crop during the winter reduced the leaching losses of N compared to no cover crop. During cotton production under relative drought, no-till and poultry litter led to somewhat elevated dissolved phosphorus concentration in runoff, and fluometuron was detected in runoff and drainage while pendimethalin was not. Fecal indicator bacteria (Escherichia coli and fecal enterococci), and the hormones estradiol and testosterone were observed in drainage and runoff but concentrations were similar across all treatments. By conducting the study for an extended period under natural environmental conditions, we were able to highlight real risks and potentials of the contrasting cropping systems. While 6 out of 14 years of relative drought might have limited the water quality response of treatments, such droughts are common features of the weather pattern in the region. Even then, use of no-till as the predominant tillage system was supported by improved yields. Fertilizer management, especially crop N need-based use of PL, requires closer monitoring to insure that production advantages of no-till and poultry litter are not offset by concerns with environmental risks. Long-term research requires sustained resource inputs to answer critical questions of environmental risk and emerging unknown issues.

A reliable laboratory index ofN availability would be useful for making N recommendations, but no single approach has received broad acceptance across a wide range of soils. We compared several indices over a range of soil conditions to test the possibility of combining indices for predicting potentially mineralizable N (N 0 ). Soils (0-5 and 5-15 cm) from nine tillage studies across the southern USA were used in the evaluations. Long-term incubation data were fit to a first-order exponential equation to determine N 0 , k (mineralization rate), and N 0 * (N 0 estimated with a fixed k equal to 0.054 wk -1 ). Out of 13 indices, five [total C (TC), total N (TN), N mineralized by hot KCI (Hot_N), anaerobic N (Ana_N), and N mineralized in 24 d (Nmin_24)] were strongly correlated to N 0 (r > 0.85) and had linear regressions with r 2 > 0.60. None of the indices were good predictors ofk. Correlations between indices and N 0 * improved compared with N 0 , ranging from r = 0.90 to 0.95. Total N and Hush of CO 2 determined after 3 d (Fl_CO2) produced the best multiple regression for predicting N 0 (R 2 = 0.85) while the best combination for predicting N 0 * (R 2 = 0.94) included TN, Fl_CO2 Cold_N, and NaOH_N. Combining indices appears promising for predicting potentially mineralizable N, and because TN and Fl_CO2 are rapid and simple, this approach could be easily adopted by soil testing laboratories.

Poultry litter (PL) can supply N, P, K, and other plant nutrients; however, excessive application may cause environmental problems, depending on management and crop nutrient demand. Changes in soil test (ST) nutrient content in a Cecil soil (a fine, kaolinitic, thermic Typic Kanhapludult) during a 10-yr period of PL use was evaluated at the USDA-ARS J. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, GA. During the cotton (Gossypium hirsutum L.) cropping phase (1995-2000), 4.4 Mg PL ha -1 yr -1 resulted in small changes in ST nutrient content in the surface 15 cm. Differences were observed between tillage treatments, with less accumulation of Ca, Mg, and Mn and greater accumulation of Zn for no-till (NT) than conventional tillage (CT). During the corn (Zea mays L.) cropping phase (2001-2005), average annual PL inputs (11.2 Mg ha -1 ) increased P and Zn contents, with changes being similar for CT and NT. After 10 yr, ST nutrient contents in the surface 15 cm reflected 25, 4, 45, 26, 17, and 97% of the input from PL for P K, Ca, Mg, Mn, and Zn, respectively. Changes in soil profile nutrient content (to a depth of 60 cm) from 1997 to 2005 were predominantly at 0 to 15 cm, where P and Zn increased >200%. Accumulation of Ca, K, P, and Zn at lower depths was also observed. Strategies for increasing nutrient removal following repeated long-term application of PL should be considered to avoid excessive levels of nutrients.

Corn (Zea mays L.) producers in the southeastern United States must overcome soil and water limitations to take advantage of the expanding corn market. In this 2001 to 2005 study on a Cecil sandy loam (fine, kaolinitic, thermic Typic Kanhapludult) near Watkinsville, GA, we compared dry land corn biomass and yield under conventional tillage (CT) vs. no-tillage (NT) with ammonium nitrate or sulfate (based on availability) as conventional fertilizer (CF) vs. poultry litter (PL). In a randomized complete block split plot design with three replications, main plots were under tillage and subplots under fertilizer treatments. The cover crop was rye (Secale cereale L.). Over 5 yr, NT and PL increased grain yield by 11 and 18%, respectively, compared with CT and CF. Combined, NT and PL increased grain yield by 31% compared with conventionally tilled and fertilized corn. Similarly, soil water was 18% greater in NT than CT in the 0- to 10-cm depth. In 2 yr of measurements, dry matter of stalks and leaves and leaf area index under PL were an average of 39 and 22% greater, respectively, than under CF during reproduction. Values were 21 and 6% greater, respectively, under NT than CT but during tasseling. Analysis of 70 yr of daily rainfall records showed that supplemental irrigation is needed to meet optimal water requirement. Our results indicate that corn growers can use rainfall more efficiently, reduce yield losses to drought, and expect increased corn yields with a combination of no-tillage management and long-term use of poultry litter.

The tropical legume sunn hemp (Crotalaria juncea L.) could be a valuable green manure/cover crop for vegetable producers in the southeastern USA because of its rapid growth and large N 2 fixing ability. Planting and termination date effects on biomass and N accumulation are relatively unknown for the region, but would help producers manage sunn hemp between summer and winter cash crops. We determined sunn hemp biomass and N content at 30, 60, 90, and 120 days after planting (DAP) for four planting dates (mid-April to mid-July) at a Piedmont and a Coastal Plain location in Georgia. Maximum biomass at a given DAP was produced from May and June plantings in the Piedmont and from April and May plantings in the Coastal Plains. Maximum biomass and N ranged from 8.9 to 13.0 Mg ha -1 and 135 to 285 kg ha -1 , respectively. An equation for estimating sunn hemp biomass as a linear function of cumulative degree days (CDD) and cumulative solar radiation (CSR) was verified with independent data from Alabama, Florida, and Virginia. A similar equation for estimating N content as a quadratic function of CSR was not as accurate but still might be useful. Sunn hemp can fit well into short-rotation sustainable vegetable production systems in the Southeast, and these equations can be used by producers to make reliable estimates of sunn hemp biomass production.

Cover crops may influence soil carbon (C) sequestration and microbial biomass and activities by providing additional residue C to soil. We examined the influence of legume [crimson clover (Trifolium incarnatum L.)], nonlegume [rye (Secale cereale L.)], blend [a mixture of legumes containing balansa clover (Trifolium michelianum Savi), hairy vetch (Vicia villosa Roth), and crimson clover], and rye + blend mixture cover cropson soil C fractions at the0‐150 mmdepth from 2001 to 2003. Active fractions of soil C includedpotentialCmineralization(PCM)andmicrobialbiomassC(MBC)andslowfraction assoilorganicC(SOC).Experiments were conducted in Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults) under dryland cotton (Gossypium hirsutum L.) in central Georgia and in Tifton loamy sand (fine-loamy, siliceous, thermic, Plinthic Kandiudults) under irrigated cotton in southern Georgia, USA. Both dryland and irrigated cotton were planted in strip tillage system where planting rows were

The type of conservation-tillage management employed could impact surface-soil properties, which could subsequently affect relationships between soil and water quality, as well as with soil C sequestration and greenhouse gas emissions. We determined soil bulk density, organic C and N fractions, plant-available N, and extractable P on Typic Kanhapludults throughout a 7-year period, in which four long-term (>10 years), no-tillage (NT) water catchments (1.3–2.7 ha each) were divided into two treatments: (1) continuation of NT and (2) paraplowing (PP) in autumn (a form of non-inversion deep ripping) with NT planting. Both summer [cotton (Gossypium hirsutum L.), maize (Zea mays L.), sorghum (Sorghum bicolor L. Moench), soybean (Glycine max L. Merr.)] and winter [wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.)] crops were NT planted throughout the study under each management system. Soil bulk density was reduced with PP compared with NT by as much as 0.15 Mg m � 3 , but the extent of reduction was inversely related to the time lag between PP operation and sampling event. Soil organic C became significantly enriched with time during this study under NT (0.49 Mg C ha � 1 year � 1 ), but not under PP, in which poultry litter was applied equivalent to 5.7 Mg ha � 1 year � 1 to all water catchments. Soil maintained a highly stratified depth distribution of organic C and N fractions and extractable P under both NT and PP. Inability to perform the PP operation in the last year of this study resulted in rapid convergence of soil bulk density between tillage systems, suggesting that PP had

Flue gas desulfurization (FGD) gypsum is a byproduct of coal-fired power plants. Its application to agricultural fields may increase water infiltration, reduce soil erosion, and decrease nutrient losses from applications of animal manures. It may also reduce fecal bacterial contamination of surface waters. We tested the hypothesis that FGD gypsum applications would decrease the load of and the fecal indicator bacterium from poultry litter applications. Two rainfall simulation experiments were undertaken: one in spring 2009 and one in spring 2011. Six treatments consisted of four rates of FGD gypsum (0, 2.2, 4.5, and 9.0 Mg ha) with poultry litter (13.5 Mg ha and two controls) in a randomized, complete-block design with three replications. Each replicate 4- × 6-m plot contained a single 1- × 2-m subplot that was delineated by metal plates and a flume that captured total overland flow or runoff. Rainfall was applied at ∼64 mm h. Volume of overland runoff was measured and subsampled for analysis every 10 min for 1 h. Flow-weighted concentrations, total loads, and soil concentrations of were determined. was not detected in runoff. No significant differences between treatments were observed for the 2009 rainfall simulation. However, after 3 yr of FGD gypsum applications, the highest rate of FGD gypsum resulted in decreased flow-weighted concentrations and total loads of . Flue gas desulfurization gypsum applications may be a management practice that reduces microbial contamination of surface waters from manure applied to agricultural fields in the southeastern United States.

Understanding cover crop and tillage system interactions within specific environments can help maximize productivity and economic returns of cotton (Gossypium hirsutum L.) produced on sandy coastal plain soils of the southeastern USA. A strip-plot design with three replications was used to evaluate the cover crops Austrian winter pea [Pisum sativum L. ssp. arvense (L.)], balansa clover (Trifolium michelianum Savi), crimson clover (Trifolium incarnatum L.), hairy vetch (Vicia villosa Roth subsp. villosa), oil seed radish (Raphanus sativus L.), black oat (Avena strigosa Schreb.), and rye (Secale cereale L.) and tillage (strip and none) influences on cotton grown on a Bonifay fine sand (loamy, siliceous, subactive, thermic Grossarenic PlinthicPaleudults)nearWaynesboro,GAfrom1999to2003.Drought influenced production 3 of 4 yr. Cover crop biomass was greatest from rye, intermediate from black oat, oilseed radish, hairy vetch, and Austrian winter pea. Hairy vetch and Austrian winter pea contained more than 80 kg N ha 21 while other cover crops averaged ,40 kg N ha 21 . Cotton yields following black oat and rye had returns above variable costs ha 21 $461 and $406, respectively. Strip-tillage increased yields by 192 kg ha 21 and annual returns by $112 ha 21 over no-tillage, most likely due to improved available water. Combining strip-tillage with black oat was the best combination for maximizing profit. Using black oat with strip-tillage could increase cotton profit by $50 to $75 ha 21 compared to systems using rye on the 1.45 million ha of cotton where conservation systems have been adopted.

Reduced tillage and residue management can have significant impacts on soil and water quality, primarily through the accumulation of soil organic C. Yet, methods of tillage and residue cover assessment are time and resource intensive, and often do not yield spatially representative results. A major goal of this study was to compare new remote sensing (RS) indices with the current line-transect approach for differentiating between conventional (CT) and conservation tillage systems. Experimental plots were located in two physiographic regions in Georgia: the Southern Piedmont and Southern Coastal Plain. Treatments consisted of no tillage (NT) or CT at the Piedmont site, and strip-tillage (ST) or CT at the Coastal Plain site. Remotely sensed data were acquired three times prior to canopy closure, using a handheld multispectral radiometer (485-1650 nm) and thermal imager (7000-14 000 nm). Soil texture and soil water content were measured to assess the impact of changes in soil background reflectance on crop residue assessments. Results showed that differences in spectral response between CT and conservation tillage systems were best observed using a normalized difference ratio of near infrared (NIR) (1650 ± 100 nm) and blue (485 ± 45 nm) spectra under dry conditions and low canopy cover (

The application of poultry litter to agricultural fields can provide plant nutrients for crops and forage production, but fecal bacteria and the sex hormones estradiol and testosterone are components of litter that can be detrimental to the environment. Our objective was to determine if applications of poultry litter to small watersheds would contribute to the load of fecal bacteria and sex hormones to soil and runoff. We, therefore, investigated the fate and transport of fecal bacteria, estradiol and testosterone from surface applied poultry litter to four small watersheds. Poultry litter was applied to meet the nitrogen requirements of pearl millet (Pennisetum glaucum L.) in 2000 and grain sorghum [Sorgham bicolor (L.) Moench] in 2001. Neither Salmonella nor Campylobacter were detected in the litter but the fecal indicator bacteria were. The average load of total coliforms,Escherichia coli, and fecal enterococci applied with the litter was 12.2, 11.9, and 12.7 log10 cells ha(−1), respectively. The average load of estradiol and testosterone was 3.1 and 0.09 mg ha(-1), respectively.Runoff events first occurred seven months after the first litter application in 2000, and three weeks after the second application in 2001.Only for the 25 July 2001 runoff event three weeks after the second litter application, were the concentrations of total coliforms, E. coli,and fecal enterococci in runoff greater than background concentrations which were on average 5.2, 1.1, and 2.9 log10 MPN 100 ml(−1),respectively [corrected]. Average background levels of total coliforms, fecal enterococci,and E. coli in surface soil were 8.2, 7.9, and 3.5 log (10) cells kg(−1) soil. At the rate of litter application the concentrations of estradiol and testosterone in the litter did not appear to impact the background levels in the soil and runoff. Because concentrations of sex hormones in litter from other broiler operations are known to be greater than in the litter we applied, further study on the connection between concentrations of sex hormones in poultry litter and operational practices is recommended.

Soil water influences hydrological, biological, and biogeochemical processes that determine on- and off-site response of landscapes under different agricultural uses. There are relatively little detailed spatial and temporal soil water measurements to validate current representations of spatial and temporal soil water variability. Soil water was measured over 3 yr at 12 sites to a 1.2-m depth in a 7.8-ha pasture catchment in the Georgia Piedmont in southeastern USA. The Mahalanobis statistical difference was estimated between all pairs of measurement sites for soil water. Multidimensional scaling of the Mahalanobis differences showed that only a single statistical dimension was separating the observed soil water variations at measurement sites (r 5 0.99). This statistical dimension was then found to be most closely correlated with the depth to the Bt and the depth of the Ap horizons for explaining the observed variation in soil water between sampling sites (r 5 0.69 and r 5 0.8, respectively). Those sites where the Bt, an argillic horizon, was close to the surface, even when higher up the landscape, were generally wetter than those in which the Bt was deeper, even in the lower part of the landscape. The depth to the Bt horizon may serve as an indicator of the portions of the watershed most likely to be primary sources of runoff in association with the depth of overlying coarse-texturedsoil.Volumetricsoilwatercontentwasgenerallygreatest

Calibration procedures and data used to parameterize a model, including model components that may or may not have been addressed, are generally not well documented in modeling studies. A comprehensive description of the process and parameters used for calibrating the Root Zone Water Quality Model, v. 1.3.2004.213, is presented in this article. The model was calibrated to simulate tile drainage and leached nitrate under conventional tillage management practices for maize (Zea mays L.) production followed by a rye (Secale cereale L.) cover crop in Cecil soils (kaolinitic, thermic, Typic Kanhapludults), and for cotton (Gossypium hirsutum L.) development in the Georgia Piedmont. Tile drainage and nitrate leaching were simulated within 15% of the observed values in the calibrated maize scenarios with and without the soil macroporosity option. Simulated and observed tile drainage and leached nitrate were not significantly different, and the simulated values were not significantly different with and without the macroporosity option. Simulated cotton biomass and leaf area index were well correlated with observed biomass and leaf area index until the last 21 d of the reproductive stage. Simulated and observed cotton water use were different by

Winter cover crops are essential in conservation tillage systems to protect soils from erosion and for improv- ing soil productivity. Black oat (Avena strigosa Schreb) and oilseed radish (Raphanus sativus L.) could be useful cover crops in the southeastern USA, but successful adop- tion requires understanding their influence on N availabil- ity in conservation tillage systems. Black oat and oilseed radish were compared to crimson clover (Trifolium incar- natum L.) and rye (Secale cereale L.) for biomass pro- duction and effects on N mineralization during the summer crop growing season from fall 1998 through summer 2002 near Watkinsville, GA. Rye produced 40 to 60% more biomass, although N contents were less than the other cover crops. Oilseed radish and black oat N contents were similar to crimson clover. Black oat, oilseed radish, and crimson clover C/N ratios were less than 30, whereas rye averaged 39. Amount of N mineralized in 90 days (Nmin90) measured with in situ soil cores was 1.3 to 2.2 times greater following black oat, crimson clover, and oilseed radish than following rye. No differences in Nmin90 were found between black oats, crimson clover, and oilseed radish in 1999 and 2000. The amount of potentially mineralizable N( N0) was not different due to cover crop, but was 1.5 times greater in 2000 and 2002 than in 1999. The rate of N mineralization (k) was 20 to 50% slower following rye than the other three cover crops. Black oat and oilseed radish biomass production and soil N mineralization dy- namics were more similar to crimson clover than to rye, which indicates that they could be used as cover crops in the southeast without significant changes in N recom- mendations for most crops.