Thermic Typic Kanhapludult Research Articles

Stratification of soil phosphorus forms from long-term repeated poultry litter applications and its environmental implication

Increasing demand for poultry products has led to an intensification of concentrated poultry feeding operations resulting in the generation of enormous amounts of poultry litter (PL). For example, in 2017 the southeastern U.S. alone generated 9.35 million U.S. tons of broiler litter. Repeated applications of PL along with no-till practices in agricultural fields located in high-density poultry operation regions often result in buildup of soil phosphorus (P) and raise environmental concerns. Less is known about how P forms such as highly reactive P (HRP), moderately reactive P (MRP), and non-reactive P (NRP) are stratified in soil layers and their potential environmental P loss risk in no-till agricultural lands that have a long-term history of PL applications. The objectives of this study were 1) to quantify the vertically distributed P forms in distinct soil depths; 2) identify the relationship between P forms and extractable P, and 3) understand the relationship between different P forms and the P saturation ratio (PSR) in PL impacted soils. Soil samples from the Madison series (Fine, kaolinitic, thermic Typic Kanhapludults) with an average 10-year PL application history on no-till agricultural fields were collected from four depths (0–5, 5–15, 15–30, and 30–45 cm) and P forms were determined using Hedley fractionation procedure. The P forms were found highly stratified within the soil layers, where the surface soils (0–5 cm) had an average of 20% of total P present in HRP, 50% in MRP, and 30% in NRP. The percentages of HRP and MRP forms decreased significantly and NRP became the dominant P form down the soil depth (15–30 and 30–45 cm). Multiple regression analysis indicated oxalate extractable P (Ox-P) represented all the three P forms (HRP, MRP, and NRP) and can be used as an index of long-term P availability. The PSR decreased down the soil profile and was linearly associated with HRP and MRP but not with NRP. Subsurface application of PL in regions where repeated loadings cannot be avoided would require careful evaluation of distinct P forms (reactive vs. non-reactive) along with the determination of soil PSR for the subsurface soil depths.

Comparison of soil health metrics for a Cecil soil in the North Carolina Piedmont

AbstractSoil health metric values may vary across soil types and even within the same soil series under different management systems. The goal of this study was to determine the amount of variation present in Cecil sandy loam soils (fine, kaolinitic, thermic Typic Kanhapludults) under row crop and hay management systems via field (single‐ring infiltration, Cornell Sprinkle Infiltrometer, and a farmer score card) and laboratory soil health metrics [soil respiration, phospholipid fatty acid (PLFA) analysis, permanganate‐oxidizable C (POXC), β‐glucosidase, β‐glucosaminidase, alkaline and acid phosphatase, arylsulfatase, phosphodiesterase, soil organic C (SOC), total N (TN), autoclave citrate‐extractable (ACE) protein content, aggregate stability, mean weight diameter, and bulk density]. Soil samples were collected in three hay and three crop fields. ANOVA indicated significant variations between systems, with depth and interactions among system, field, and/or slope position, depending on the metric (p < 0.05). Infiltration measurements were highly variable and the measurement methods produced inconsistent values. The majority of laboratory metrics significantly decreased with depth. Soil respiration was significantly different between systems (crop > hay), whereas arylsulfatase, acid phosphatase, β‐glucosidase, β‐glucosaminidase, ACE, POXC, and aggregate stability had significant system × depth interactions (0–5 cm hay > crop) and POXC had a significant system × pedon interaction. Enzyme assays, PLFA measurements, POXC, TN, SOC, and ACE protein content were also significantly correlated with each other. Unexpected trends and variable results suggest that more data should be collected before effective soil health metrics and baseline values can be established.

Landscape, Soil, and Plant Analysis of Japanese Stiltgrass (Microstegium vimineum) Invasion in the Piedmont Region, SC

ABSTRACTJapanese stiltgrass (Microstegium vimineum), an exotic invasive plant, is native to Southeast Asia. This study was conducted to determine the chemical composition of Japanese stiltgrass as well as soil and landscape characteristics that correlate with invasion of Japanese stiltgrass around Lake Issaqueena in the upper Piedmont of South Carolina. Geographic Information Systems (GISs) and Light Detection and Ranging (LiDAR) were used to determine the spatial pattern of invasion with respect to the aspect, slope, canopy cover, soils, and distance to roads and trails. Japanese stiltgrass was distributed on both sides of Lake Issaqueena in Pacolet and Madison soil map units (Fine, kaolinitic, thermic Typic Kanhapludults) on the average slopes of 21%, but it was particularly common on the eastern shore of the lake in low-lying wet and shaded areas (mean canopy cover 51%). In addition, invasion by Japanese stiltgrass was correlated with the proximity to roads and trails. Plant tissue analysis revealed many differences in the distribution of macronutrients, macrominerals, and micronutrients in the leaves, stems, and roots of Japanese stiltgrass, although those differences were not always statistically significant. Concentrations of nitrogen (N), phosphorus (P), and calcium (Ca) were the highest in leaves while zinc (Zn) concentrations were the highest in stems and concentrations of magnesium (Mg), copper (Cu), manganese (Mn), iron (Fe), and sodium (Na) tended to be higher in roots. Carbon (C), sulfur (S), and potassium (K) concentrations were generally higher in above-ground tissues versus roots. Soil chemical analysis revealed no statistical differences between control and invaded plots. Our findings suggest that watershed areas surrounding lakes may be particularly susceptible to the invasion of Japanese stiltgrass due to their microclimates, low-lying wet pathways for seed distribution and recreational uses.

Nitrogen fertilizer sources and tillage effects on cotton growth, yield, and fiber quality in a coastal plain soil

Interest in urea-ammonium sulfate (UAS) as a N fertilizer is increasing due, in part, to increased restrictions on ammonium nitrate. This has resulted in UAS being marketed as an alternative fertilizer source; however, UAS has not been widely tested. A cotton (Gossypium hirsutum L.) field study was conducted in Central Alabama from 2009 to 2011 on a Coastal Plain soil (Marvyn loamy sand; fine-loamy, kaolinitic, thermic Typic Kanhapludult) comparing UAS to two common granular fertilizers [urea, ammonia sulfate (AS)] under both conservation and conventional tillage systems. The overall objective was to determine the influence of UAS on cotton growth parameters, yield, and fiber quality. Cotton was fertilized with 101kgNha−1 urea, AS, or UAS 5–6wk after planting each year. Plant growth characteristics were evaluated 3–4wk before defoliation, and cotton yield and fiber quality were determined on the machine-harvested lint. Tillage had little influence on plant growth, while UAS and/or AS tended to produce the largest number of bolls and largest aboveground, root, and total biomass in 2009 and 2011. Lint yield was also influenced by fertilizer source in 2009 and 2011, with UAS and AS producing significantly higher yields than urea. Both tillage and fertilizer source had minimal influence on cotton fiber quality. Results suggest that UAS produces similar or greater yields than urea and is comparable to AS. However, more research is needed to determine the long-term influence of UAS on soil acidity and N loss compared to urea and AS.

Carbon Dioxide Flux from Bermudagrass Turf as Affected by Nitrogen Rate

Increasing carbon dioxide (CO2) concentrations have contributed to global climate change. Atmospheric CO2 concentration has increased by ≈43%, from 280 ppmv in 1850 to 400 ppmv in 2015. This increase is expected to alter the distribution of C among the atmosphere, vegetation, and soils. Despite its large‐scale presence in the urban ecosystem, the role of turfgrasses in C cycling has received limited attention, and studies with warm‐season turfgrasses are lacking. The objective of this study was to estimate CO2 flux from soil as affected by N applied to bermudagrass [Cynodon dactylon (L.) Pers. C. transvaalensis Burtt Davy]. The study was initiated in March 2012 on 8‐yr‐old Tifway hybrid bermudagrass plots located at the Auburn University Turfgrass Research Unit on a Marvyn loamy (fine‐loamy, kaolinitic, thermic Typic Kanhapludult) sand soil. The experimental design was a randomized complete block with four N rates of 24, 49, 98, and 196 kg N ha−1 yr−1 that were replicated three times. Carbon dioxide flux was measured weekly for 95 wk using an automated soil CO2 flux system (LiCor LI‐8100A, LICOR, Inc., Lincoln, NE). Soil temperature and moisture were also determined during CO2 flux measurements. Results showed strong correlation between CO2 flux and N rate (r2 = 0.99∗∗). Accumulated CO2 flux increased by 35%, from 107 to 144 Mg ha−1 as N rate increased from 24 to 196 kg N ha−1, respectively. Data suggest that a lower N application rate may be a better choice for mitigation of CO2 emissions under bermudagrass management.Core Ideas Averaged daily fluxes of CO2 were significantly (r2 = 0.99∗∗) correlated with N rate. Lower N application rate may be a better choice for mitigation of CO2 emissions under bermudagrass management. Increasing soil temperature has increased CO2 fluxes.

Geospatial Soil and Plant Tissue Analysis of Sericea Lespedeza (Lespedeza cuneata) Invasion around Lake Issaqueena, South Carolina

ABSTRACTThis study was conducted to determine the chemical composition of sericea lespedeza (Lespedeza cuneata) as well as soil and landscape characteristics that correlate with its invasion. Geographic Information Systems (GIS) and Light Detection and Ranging (LiDAR) were used to determine the pattern of invasion and to quantify landscape metrics. Sericea lespedeza was distributed on both sides of the lake in Pacolet and Madison soil map units (Fine, kaolinitic, thermic Typic Kanhapludults) on average slopes of 17.5%. It was common along roads and trails with a preferred mean canopy cover of <50%. Plant tissue analysis revealed statistically higher concentrations of macronutrients nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca) and sulfur (S) and selected micronutrients in leaves compared to stems and roots. Micronutrients copper (Cu), manganese (Mn) and iron (Fe) were significantly higher in stems and roots. Soil analysis results showed no statistical difference between control and invaded plots for measured soil chemistry parameters.

Carbon Sequestration under Warm Season Turfgrasses in Home Lawns

Turfgrass cover in the U.S. is expanding because of increasing urbanization and the addition of approximately 675,000 ha of residential property every year. Despite its large-scale presence in the urban ecosystem, the role of turfgrasses in carbon (C) cycling in home lawns in southeastern U.S. soils has not been documented, and studies with warm-season turf grasses are lacking. The objective of this study was to estimate carbon (C) sequestration in soil as affected by turfgrass species, including: bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy), centipede grass (Erecholmoa ophroides (Munroe) Hack.), and zoysiagrass (Zoysia spp.). The study was initiated in the winter of 2012 and conducted for two years on a loamy sand (fine-loamy, kaolinitic, thermic Typic Kanhapludult) soil. Eighteen lawns were sampled twice per year: six lawns of each grass species, with the harvested grasses separated into stems, above ground biomass (verdure) + thatch, and belowground roots. Soil samples (0 - 5, 5 - 10, and 10 - 20 cm) were also collected. Total C concentration was determined on finely ground-dried samples by combustion. Turfgrass species, season and years of sampling were all significantly (P ≤ 0.05) affected by C sequestration. Zoysiagrass had the highest mean levels of sequestered C, with a value of 5.54 ± 0.21, compared to 2.09 ± 0.11 and 4.23 ± 0.14 Mg·ha-1·yr-1 under bermudagrass and centipedegrass at the end of the study, respectively. This work indicates that turfgrass home lawns may be an important contribution to the global carbon sequestration level.

Evaluation of an inexpensive sensor to measure soil color

Soil color determination can be subjective due to environmental conditions and human error. The objectives of this study were to examine the precision of a relatively inexpensive color sensor (NixTM Pro); to compare soil color measurements using this color sensor to human determination by soil science professionals using the standard Munsell Color Chart; and to compare the accuracy of this color sensor to a laboratory standard colorimeter (Konica Minolta CR-400). Sensor measurements were compared to the soil color chart by converting the Nix Pro values to Munsell soil color codes using BabelColor conversion software. Thirty-one Cecil (Fine, kaolinitic, thermic Typic Kanhapludults) soil samples were collected and tested for color. Munsell color codes were converted into cyan, magenta, yellow, and black (CMYK) color values, and the Nix sensor’s scan results were tested against predetermined Munsell color values and colorimeter CMYK color values using correlation analysis for all treatments. Nix Pro Color Sensor was precise in soil color determination and it was more accurate than the Munsell Color Chart and comparable to the Konica Minolta CR-400 for both dry and moist soil. The Munsell Color Chart was accurate compared to the Konica Minolta CR-400 in dry soil, but it was less accurate in moist soil. The Nix Pro Color Sensor can be a successful tool to measure soil color in the standard Munsell color codes and this study presents a step-by-step method for converting sensor measurements to the standard Munsell color codes.

Stratification of Phosphorus Forms from Long-Term Conservation Tillage and Poultry Litter Application

Phosphorus stratification leaves high P concentrations at the soil surface, which are vulnerable to loss in runoff. Understanding P forms at the soil surface may help control P loss, but little information is available on how P forms stratify in soils. We used 31P nuclear magnetic resonance (NMR) spectroscopy and chemical analysis to characterize P forms and the elements controlling P cycling in Cecil soil (a fine, kaolinitic, thermic Typic Kanhapludult) that became P stratified after 11 yr of cropping management conducted under combinations of tillage (conventional and no-till, CT and NT, respectively) and inorganic chemical (CF) and poultry litter (PL) fertilization. Samples from three soil depths (0–2.5, 2.5–5, and 5–15 cm) were sequentially extracted in NaOH–ethylenediaminetetraacetic acid (EDTA) and HCl before 31P-NMR spectroscopy. The NaOH–EDTA extraction recovered 63 to 83% of the total P in a range of P forms, and HCl recovered 2 to 16% of the total P, mainly orthophosphate. Phosphorus forms and concentrations were evenly distributed in soil layers only in the CT treatment with CF. Stratification of orthophosphate and phytate occurred in NT samples fertilized with PL and CF, with the highest concentrations in the top 2.5 cm. Increased orthophosphate and phytate concentrations were detected at the soil surface for CT–PL samples, indicating that PL is not as well mixed by tillage as CF. These results suggest that P fertilizers should be placed below the soil surface under NT to avoid stratification and thus reduce potential P loss in surface runoff.

Enhanced‐Efficiency Fertilizer Effects on Cotton Yield and Quality in the Coastal Plains

Interest in the use of enhanced‐efficiency nitrogen fertilizer (EENFs) sources has increased in recent years due to the potential of these new EENF sources to increase crop yield, while at the same time decreasing N loss from agricultural fields. The efficacy of these fertilizer sources on cotton (Gossypium hirsutum L.) production in southeastern U.S. upland soils has not been well documented. Thus, a field study was conducted on a Coastal Plain soil (Marvyn loamy sand; fine‐loamy, kaolinitic, thermic Typic Kanhapludult) in Central Alabama from 2009 to 2011 to compare EENFs to traditional N sources in a high‐residue conservation cotton production system. Nitrogen fertilizer sources evaluated included urea (U), ammonium sulfate (AS), urea‐ammonium sulfate (UAS), Environmentally Smart Nitrogen (ESN) (Agrium Advanced Technologies, Loveland, CO), stabilized urea (SuperU [SU] [Agrotain International, St. Louis, MO]), poultry litter (PL), poultry litter + AgrotainPlus (PLA) (KOCH Agronomic Services LLC, Wichita, KS), and an unfertilized control (C). Generally, no significant differences in cotton lint yield were observed between the traditional sources and EENFs. Nitrogen source affected fiber quality; however, effects varied among years and generally would not have impacted discount/premium values. In the present study, EENFs produced cotton lint yields similar to conventional fertilizers, suggesting their higher cost may render them uncompetitive at present. However, if EENFs reduce N loss through leaching, runoff and N2O flux from agricultural fields they could become viable alternative fertilizer sources. More research is needed on the benefits of enhanced‐efficiency fertilizer use as a tool in agricultural production systems.

Effects of Drought on Nutritive Value of Kudzu

Kudzu (Pueraria montana), a vigorous, perennial warm-season invasive legume is widely spread in the southeastern United States and has the potential to be used as feed by ruminants during its growing season from May until first frost (usually in October). The purpose of this study was to determine the nutritive value of kudzu during a drought-prone growing season. Five samples of apical leaves and stems were harvested once a week from random locations within a 43-year-old kudzu infestation grown on a Cecil clay loam (fine, kaolinitic, thermic Typic Kanhapludults) at the Clemson University Experimental Forest (Clemson, S.C.). We report the effects of plant part, sampling date, mean air temperature (MAT), and precipitation on dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), calcium (Ca), magnesium (Mg), phosphorus (P), potassium (K), sulfur (S), zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe) of the kudzu. Dry matter and CP were significantly greater in the apical leaf than in the stem; CP had a significant mean air temperature by plant part interaction. A significant temperature by plant part interaction also existed for Mg. Magnesium was greater in leaf than in the stem at the beginning of the growing season until the end of October, when small differences in Mg concentrations between stem and leaf were observed. Stem and leaf Ca concentrations were not significantly different. Calcium concentrations did vary across the dates (P = 0.002). A significant temperature by plant part interaction existed for Mg concentrations (P = 0.003), Ca to P ratio (P < 0.0001), P concentrations (P = 0.0007), S (P < 0.0001), Zn (P = 0.0053), Mn (P = 0.0014), and Cu (P = 0.006). Overall, kudzu's nutritive value as feed for ruminants during the growing season is highly variable; however, chemical composition was very comparable to other common forages. More frequent and intensive droughts predicted as a result of climate change may limit forage choices; however, kudzu maintains its forage potential for feeding both domestic and wild animals during drought-prone growing season.

Partial Shade, Irrigation, and Added Nutrients Maximize Dry Matter Yield of American Skullcap (Scutellaria lateriflora L.)

American skullcap (Scutellaria lateriflora L.), a medicinal plant species valued for its sedative properties associated with flavonoids, is generally harvested from the wild. Scientific information on how field cultivation practices affect dry matter yield is lacking in this species. A 2 × 2 × 3 split plot factorial experiment within a randomized complete block design was conducted on a Marvyn loamy sand (fine-loamy, kaolinitic, Thermic Typic Kanhapludults) in Central Alabama to explore effects of light, irrigation, and nutrient application on dry matter yield of American skullcap. Treatment factors were shade (40% shade vs. no shade), irrigation (applied at 30 kPa vs. no irrigation), and nutrients [no added nutrients vs. nutrients added as chemical fertilizer (100 kg nitrogen, 68 kg phosphorus, 42 kg potassium/ha) or chicken litter (100 kg nitrogen, 50 kg phosphorus, and 123 kg potassium/ha)]. Shade formed the main plot units, whereas irrigation × nutrient factorial combinations were subplots. Skullcap shoots in experimental plots were harvested four times during the course of the two-year experiment (2007, 2008). All growth variables measured, except percent dry matter, performed better under shade than in full sun. Dry matter yield was increased 45% by shade, 61% by irrigation, and 22% by addition of nutrients. A significant irrigation × nutrients interaction was observed at the first and second harvests. Highest yields were obtained with the irrigation + manure and irrigation + fertilizer treatments under shade and the lowest with fertilizer and the control treatments in full sun.

Nitrate, Ammonium, and Urea Leaching in Hybrid Bermudagrass as Affected by Nitrogen Source

Nitrate leaching in turfgrass has been widely studied and found to increase when N was over‐applied, soluble N sources were used, N was applied to sandy soils, or excessive irrigation was applied. The objective of this study was to evaluate N leaching as nitrate, ammonium, and urea from hybrid bermudagrass on three soils (Sumter clay [fine‐silty, carbonatic, thermic Rendollic Eutrudept], Marvyn loamy sand [fine‐loamy, kaolinitic, thermic Typic Kanhapludult], and sand) with three N sources (urea, polymer‐coated urea, urea plus nitrification/urease inhibitor) and a control. Field lysimeters were fertilized at 7.3 g N m−2 in July, and leachate collected for 10 to 12 wk each year for 2 yr. Leachate was analyzed for nitrate‐N, ammonium‐N, and urea‐N. In the first year, significant nitrate‐N was collected, regardless of N source. In that year nitrate‐N in leachate from the clay soil frequently exceeded 10 mg N L−1, even in the unfertilized treatment. High organic matter in the clay soil and N mineralization following construction contributed to nitrate leaching. In the second year, nitrate‐N in leachate never exceeded 10 mg N L−1, regardless of N source or soil type. Differences in total nitrate‐N and ammonium‐N leached due to N source were found in the loamy sand and sand soils, typically in the order: urea ≥ urea + inhibitor ≥ polymer‐coated urea = unfertilized control. Small quantities of urea‐N leached throughout the experiments. If applied at a recommended rate to established turfgrass, leaching of N did not present an environmental hazard. Use of a slow‐release N source sometimes further reduced N losses in leachate.

Subsurface Application of Poultry Litter and Its Influence on Nutrient Losses in Runoff Water from Permanent Pastures

Environmental pressure to reduce nutrient losses from agricultural fields has increased in recent years. To abate this nutrient loss to the environment, better management practices and new technologies need to be developed. Thus, research was conducted to evaluate if subsurface banding poultry litter (PL) would reduce nitrogen (N) and phosphorus (P) loss in surface water runoff using a four-row prototype implement. Rainfall simulations were conducted to create a 40-min runoff event in an established bermudagrass (Cynodon dactylon L.) pasture on soil types common to the Coastal Plain and Piedmont regions. The Coastal Plain soil type was a Marvyn loamy sand (fine-loamy, kaolinitic, thermic Typic Kanhapludults) and the Piedmont soil type was a Hard Labor loamy sand (fine, kaolinitic, thermic Oxyaquic Kanhapludults). Treatments consisted of surface- and subsurface-applied PL at a rate of 9 Mg ha(-1), surface broadcast-applied commercial fertilizer (CF; urea and triple superphosphate blend) at the equivalent N (330 kg N ha(-1)) and P (315 kg N ha(-1)) content of PL, and a nonfertilized control. The greatest loss for inorganic N, total N, dissolved reactive P (DRP), and total P occurred with the surface broadcast treatments, with CF contributing to the greatest loss. Nutrient losses from the subsurface banded treatment reduced N and P in surface water runoff to levels of the control. Subsurface banding of PL reduced concentrations of inorganic N 91%, total N 90%, DRP 86%, and total P 86% in runoff water compared with surface broadcasted PL. These results show that subsurface band-applied PL can greatly reduce the impact of N and P loss to the environment compared with conventional surface-applied PL and CF practices.

Nitrogen, Phosphorus, and Liming Effects of Poultry Layer Manures in Coastal Plain and Piedmont Soils

Since soil type and manure processing can affect nutrient release, laboratory and greenhouse experiments determined N and P availability, and liming value under representative layer manure application scenarios. Fresh, composted, and pelleted manures were applied to surface samples of three North Carolina soils (Belhaven, loamy, mixed, dysic, thermic Terric Haplosaprists; Cecil, fine, kaolinitic, thermic Typic Kanhapludults; and Lynchburg, fine‐loamy, siliceous, semiactive, thermic Aeric Paleaquults). A 90 d N mineralization incubation found greater N mineralization (83, 73, and 61% of total N applied in fresh, composted, and pelleted manures, respectively), in the Lynchburg than in the Cecil soil (41, 33, and 25% for the same manures); while mean N availability of urea was 80% for all soils. All manures exhibited effects on soil pH and Mehlich‐3 extractable soil P during separate 21 d incubations that were consistent with their calcium carbonate equivalence and total P content. In a 30 d greenhouse experiment with millet [Urochloa ramosa (L.) T. Q. Nguyen] in the same soils, plant available N from the manures followed the decreasing order of fresh &gt; composted &gt; pelleted, similar to the rank order obtained in the N incubation study. Application of either inorganic or manure P sources to the Belhaven muck resulted in more water soluble soil P and greater plant P uptake than when P was applied to the mineral soils. Both soil and manure source influenced manure nutrient availability, but the availability coefficients from these laboratory and greenhouse experiments should be verified under field conditions.

Steer Performance and Pasture Productivity of Caucasian Bluestem at Three Forage Masses

The introduced perennial, warm‐season grass, Caucasian bluestem [Bothriochloa caucasia (Trin.) C.E. Hubbard ‘Caucasian’], appears to be adapted to the mid‐Atlantic region. This 4‐yr experiment compared animal and pasture productivity of Caucasian bluestem over three canopy heights, or forage masses (FM), designated as Short (14.6 cm), Medium (32.2 cm), and Tall (39.8 cm). The relationship of canopy height to diet and canopy characteristics was also evaluated. The soil was a Cecil clay loam (fine, kaolinitic, thermic Typic Kanhapludult). Pastures were continuously stocked using variable stocking from mid‐May through mid‐September. Forage mass (harvested to a 2.5‐cm stubble), increased linearly (P = 0.04) averaging 1.42, 2.31 and 2.75 Mg ha−1 for Short, Medium, and Tall canopy heights. Steer average daily gain (ADG) was similar among FM treatments (0.76 kg d−1) but weight gain decreased linearly (P &lt; 0.01) from Short to Tall (from 817 to 518 kg ha−1). Increasing FM resulted in a quadratic decrease (P ≤ 0.04) in stocking rate (from 9.7 to 7.8 steers ha−1) and animal days (from 1019 to 700 d ha−1) and a linear decrease (P = 0.02) in effective feed units (from 4025 to 2806 kg ha−1). Stand counts of Caucasian bluestem increased linearly (P = 0.05) from Tall to Short FM (from 22.8–70.0%) with the Tall providing openings for potential weed invasion. Caucasian bluestem can be heavily stocked and may provide acceptable quality forage for summer grazing in the mid‐Atlantic region.

Cover crop and tillage effects on soil enzyme activities following tomato

Increasing numbers of vegetable growers are adopting conservation tillage practices and including cover crops into crop rotations. The practice helps to increase or maintain an adequate level of soil organic matter and improves vegetable yields. The effects of the practices, however, on enzyme activities in southeastern soils of the United States have not been well documented. Thus, the objectives of the study were to investigate the effects of cover crops and two tillage systems on soil enzyme activity profiles following tomato and to establish relationships between enzyme activities and soil organic carbon (C) and nitrogen (N). The cover crops planted late in fall 2005 included black oat ( Avena strigosa), crimson clover ( Trifolium incarnatum L.), or crimson clover–black oat mixed. A weed control (no cover crop) was also included. Early in spring 2006, the plots were disk plowed and incorporated into soil (conventional tillage) or mowed and left on the soil surface (no-till). Broiler litter as source of N fertilizer was applied at a rate of 4.6 Mg ha −1, triple super phosphate at 79.0 kg P ha −1, and potassium chloride at 100 kg K ha −1 were also applied according to soil testing recommendations. Tomato seedlings were transplanted and grown for 60 days on a Marvyn sandy loam soil (fine-loamy, kaolinitic, thermic Typic Kanhapludults). Ninety-six core soil samples were collected at incremental depths (0–5, 5–10, and 10–15 cm) and passed through a 2-mm sieve and kept moist to study arylamidase (EC 3.4.11.2), l-asparaginase (EC 3.5.1.1), l-glutaminase (EC 3.5.1.2), and urease (EC 3.5.1.5) activities. Tillage systems affected only l-glutaminase activity in soil while cover crops affected activities of all the enzymes studied with the exception of urease. The research clearly demonstrated that in till and no-till systems, l-asparaginase activity is greater ( P ≤ 0.05) in plots preceded by crimson clover than in those preceded by black oat or their mixture. Activity of the enzyme decreased from 11.7 mg NH 4 +–N kg −1 2 h −1 at 0–5 cm depth to 8.73 mg NH 4 +–N kg −1 2 h −1 at 5–10 cm and 10–15 cm depths in the no-till crimson clover plots. Arylamidase activity significantly correlated with soil organic C ( r = 0.699**) and soil organic N ( r = 0.764***). Amidohydrolases activities significantly correlated with soil organic N but only urease significantly correlated with soil organic C ( r = 0.481*). These results indicated that incorporation of cover crops into rotations may increase enzyme activities in soils.

Soil Drying Effects on Spatial Variability of Soil Hardpan Attributes on Pacolet Sandy Loam Soil

Soil hardpans found in many of the southeastern U.S. soils reduce crop yields by restricting the root growth. Site-specific soil compaction management to alleviate this problem requires determination of the spatial variability and mapping of soil hardpans. The objective of this study was to determine the spatial variability of soil hardpan as influenced by soil moisture. Geo-referenced soil cone index measurements were taken in 200 grid cells (10 m × 10 m grid cell size) on Pacolet sandy loam soil (fine, kaolinitic, thermic Typic Kanhapludults) in Auburn, Alabama, on 29 June and 25 August 2004, representing and soil measurement dates. Core samples were also taken in 5 cm depth increments up to a depth of 65 cm for soil moisture and bulk density determinations. Statistical and geostatistical methods were used for the data analysis. In the 0-35 cm depth, the soil moisture had dried significantly by 25 August 2004 (dry) as compared to the soil moisture on 29 June 2004 (wet; P < 0.0001). An isotropic spherical semivariogram model best fit the semivariances of the peak cone index for wet (R 2 = 0.98) and dry (R 2 = 0.97) soil conditions. Soil drying increased the peak cone index and the maximum semivariance value (sill). Small but statistically significant differences (P < 0.0001) were also observed on the depth to the peak cone index as the soil dried in the 0-35 cm depth. In the dry soil condition, the semivariances of the depth to the peak cone index were nearly constant over the separation distances, suggesting that the depth to the hardpan did not exhibit substantial spatial dependence.

Soil Test Nutrient Changes Induced by Poultry Litter under Conventional Tillage and No‐Tillage

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 &gt;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.

Animal and Pasture Productivity of ‘Coastal’ and ‘Tifton 44’ Bermudagrass at Three Nitrogen Rates and Associated Soil Nitrogen Status

‘Coastal’ and ‘Tifton 44’ (T44) bermudagrass [Cynodon dactylon (L.) Pers.] are well adapted across the lower southern United States, but the grazing response of (T44) to N application in the Piedmont of the upper South warrants further evaluation. This 3‐yr experiment compared animal and pasture productivity of Coastal and T44 with three annual N rates of 101, 202, and 303 kg of N ha−1 on a Cecil clay loam (fine, kaolinitic thermic Typic Kanhapludult) soil typical of the Piedmont. Herbage mass differed for Coastal and T44 (3.5 and 3.0 Mg ha−1 respectively, P &lt; 0.01), but not among N rates. The canopy of T44 was leafier (20.6 vs. 14.5% of dry matter) than Coastal and greater for in vitro true organic matter disappearance (IVTOD) (522 vs. 498 g kg−1) and CP (107 vs. 84 g kg−1) and lesser in NDF (596 vs. 605 g kg−1). The diet selected from T44 was greater in IVTOD (764 vs. 743 g kg−1) and lesser in NDF (596 vs. 605 g kg−1) giving greater steer average daily gain (0.63 kg vs. 0.57 kg; P &lt; 0.01) which increased (P = 0.05) with N rate. Weight gain ha−1 (884 kg) and effective feed units (EFU) (4735 kg ha−1) were similar, and N rate linearly increased gain from 723 to 1073 kg ha−1 and EFU from 3978 to 5523 kg ha−1. Soil inorganic N was similar between cultivars but differed among soil depths. Tifton 44 pasture was greater in nutritive value, hence steer performance, and as productive as Coastal in the Piedmont.