Measuring and mapping apparent soil electrical conductivity (ECa) is a potentially useful tool for delineating soil variability. The "Old Rotation," the world's oldest continuous cotton (Gossypium hirsutum L.) experiment (ca. 1896), provides a valuable resource for evaluating soil spatial variability. The objectives of this study were to determine the relationship between soil chemical and physical properties and ECa in the Old Rotation, to determine spatial differences in these properties, and to relate differences in these properties to long-term management effects. Soils at the site classified as fine, kaolinitic, thermic Typic Kanhapludults. Soil ECa was measured at 0-30- and 0-90-cm depths (ECa-30 and ECa-90) using a Veris((R)) 3100 direct contact sensor with georeferencing. Soils were grid sampled (288 points) at close intervals (1.5 x 3.0m) for chemical properties and grid sampled (65 cells, 7.5 x 6.9 m) for soil texture. Soil organic carbon (SOC) and total nitrogen (N), extractable phosphorus (P), potassium (K), calcium (Ca), pH, buffer pH, and estimated cation exchange capacity (CECest) were measured at two depths (0-5- and 5-15-cm). Soil ECa was highly spatially correlated. The ECa-30 was more highly correlated with clay content (r = 0.58, P <= 0.01) and P(r = 0.43, P <= 0.01) than other soil properties. Total nitrogen and SOC had little or no relationship with ECa-30. Cropping systems affected chemical properties in the Old Rotation, indicating crop rotation and cover crops are beneficial for soil productivity. The relatively poor relationship between soil chemical parameters and ECa suggest that mapping plant nutrients and SOC using ECa is problematic because of strong dependence on clay content.

Land application of poultry broiler litter (BL) in agricultural production is a widely used practice. However, cotton ( Gossypium hirsutum L.) growers in poultry‐producing regions of the southern USA have been reluctant to use BL as a crop nutrient source. Field experiments were conducted for 13 yr to study the effect of BL application to cotton and corn ( Zea mays L.) under conventional and conservation tillage systems. Nitrogen rates from 0 to 269 kg ha −1 were applied annually at two locations to compare the effect of BL and ammonium nitrate (AN) as N sources. The relationship between the total N rates ( N ) applied and the relative N availability ( y ) based on the crop yield by application of BL and AN is described by linear equation: y = 71.58 + 0.15 N ( r = 0.66). In most years, there were no differences in relative yields from total N applied as BL or AN. The amplitude of yield increase based on N source varied with rainfall during the growing season. The residual effect of BL in the second year after application resulted in 30 to 50% of the cotton lint yield and 25 to 65% of the corn grain yield that resulted from a standard N fertilization rate. General observations suggest that N availability from BL is similar whether surface‐applied as in conservation tillage systems or incorporated as in conventionally tilled systems.

We present a laboratory investigation of Alfvén wave refraction due to a gradient in the plasma beta along the magnetic field. Theoretically, it is expected that perpendicular wave refraction occurs when the Alfvén wave changes from kinetic to inertial, as occurs along a typical auroral field line. The change in propagation characteristics is expected to produce a focusing of the wave energy. In the Earth's magnetosphere it is thought that this refractive property may play a key role in the field line resonance process. This effect is observed in the laboratory by creating a plasma with a parallel gradient of 100 per 105 Debye lengths. An Alfvén wave is then launched with an antenna, and the field patterns of the wave are observed at several axial locations.

Soil organic carbon (SOC) changes in long-term experi­ ments can provide valuable information r egarding manage­

An experimental study of the response to an impulsive driver in a low beta helium plasma is presented. Field line resonance (FLR) spectra are recorded and compared to an ideal magnetohydrodynamic (MHD) theory with finite ion cyclotron frequency corrections. The agreement between observed and predicted values is generally within the frequency resolution of the measurements except for the lowest frequency harmonic. The spectrum of the lowest harmonic is compared to various ultra low-frequency (ULF) FLR dispersion relations. Dispersion effects due to nonzero perpendicular wave number are found to be important for the lowest frequency harmonic. Quality factors are measured and compared to theoretical estimates from a two-fluid theory with finite parallel electron temperature. Reflection coefficient values are obtained using measured and estimated Q values.

After 106 cr opping years, Alabama's Old Rotation ex­

Experiments on the edge plasma of tokamaks have discovered magnetic fluctuations which are highly correlated along the magnetic field, and are correlated with scale size of the electron inertial length (delta = c/omega (pe)) across the field. They are, in all probability, shear Alfven waves. The FREJA, FAST, and Interball satellites have frequently encountered density striations in the auroral ionosphere. These can be narrow, also of the order of delta. Intense wave activity has been measured within these structures and tentatively identified as shear inertial (V-A > V-the) Alfven waves. These waves have been studied in great derail in the Large Plasma Device at UCLA. The plasma, which is 10 m in length and 500 ion Larmor radii in diameter (He (lambda (parallel to) approximate to 2 m), Ar (lambda (parallel to) approximate to 10 m, 1.5 kG, 40 cm plasma diameter, n = 1.0-4.0 x 10(12) cm(-3), fully ionized) supports Alfven waves. Our initial investigations, which will be briefly reviewed, involved low-amplitude (deltaB(wave)/B-0 approximate to 10(-4)) shear waves launched by modulating a skin depth size current channel, and have examined the wave characteristics in the kinetic (V-A < V-the) and inertial regimes and in magnetic field gradients. Launching higher-power waves (B-wave/B-0 greater than or equal to 10(-3)) waves with the use of a helical antenna has extended these studies. Both shear Alfven waves (omega < (ci)) and compressional Alfven waves have been investigated. Below f(cl) the wave fields slowly spread across the background magnetic field and the current associated with it forms a rotating spiral. The higher-power wave causes a localized density perturbation when deltaB(wave)/B-0 exceeds 10(-3) even when the wave propagates below the cyclotron frequency. The perturbation is measured using Langmuir probes as well as laser-induced fluorescence (LIF) signal from Ar II ions. We present data of the wave propagation in which the temporal history of the vector magnetic field was acquired at 20 000 spatial locations. The data is used to calculate 3D wave currents, wave phase fronts and energy propagation. In helium the wave pattern is more complex than in argon. We also present the space and time evolution of the density perturbations associated with the wave in an Ar plasma. LIF data was used to directly measure the ion motion in the electric field of the wave, ion polarization currents and the motion of the ions as they form the density non-uniformities.

We present laboratory observations of shear Alfvén wave resonances in a cylindrical plasma column. Fourier data are presented which show the existence of many standing eigenmodes in the shear Alfvén frequency range. Harmonic frequency dependence on ambient is presented for three resonances. A wavelet analysis is used to show the lifetimes of the identified harmonic modes. Experimental Q values for the first five eigenfrequencies are measured and compared to theoretical values.

In order to determine the effects of lagoon effluent application on soil chemical properties, swine lagoon effluent was applied to land with a 10% slope by an overland flow irrigation system on hybrid bermudagrass (Cynodon dactylon L. Pers.) and annual ryegrass (Lolium multiform Lan). Treatments included a control with no nutrient additions, ammonium nitrate at 560 kg N ha−1 yr−1, and swine lagoon effluent at 560, 1120, and 2240 kg N ha−1 yr−1. Soil on the research site is a Marvyn loamy sand (fine-loamy, siliceous, thermic, Typic Kanphapludults). At the termination of the experiment, soil core samples were taken to 120 cm, and depth-incremental samples were analyzed for total C, NH4-N, NO3-N, Mehlich-I extractable P, K, Ca, Mg, Cu, Zn, and Mn, soil pH and electrical conductivity. Treatment had no significant effects on soil NH4-N and extractable soil Cu, Zn, and Mn concentrations. Lagoon effluent application did not increase soil total C. Lagoon effluent and ammonium nitrate applications supplying the N loading resulted in a buildup of NO3-N, especially for the high N loading rate. Soil NO3-N in the lower depths throughout soil profiles reached approximately 30 mg kg−1. Application of lagoon effluent resulted in significant P buildup to a depth of 40 cm. Mehlich-I extractable P accumulated to as high as 115 mg kg−1 on the upper portion and 40 mg kg−1 on the lower portion of the sloping land in the surface 0–20 cm soil layer. Extractable soil K concentration increased with increasing rates of lagoon effluent application. The application of swine lagoon effluent resulted in a decrease in soil pH and an increase in soluble salt accumulation.

The Old Rotation cotton experiment at Auburn, Alabama, is the oldest, continuous cotton experiment in the world (cf. 1896). Long-term cropping systems provide a unique opportunity to observe the effects of 100 years of cropping on soil organic carbon (SOC). The objective of this paper was to summarize limited data on SOC and N cycling in this historic experiment. Soil organic C has been measured on the 13 plots (6 cropping systems) in 1988, 1992 and 1994. Long-term planting of winter legumes with no other source of N applied resulted in higher SOC (9.5 g C kg−1) in the plow layer (0–20 cm depth) compared to continuous cotton with no winter cover crops (4.2 g C kg−1). A 3-year rotation of cotton–winter legumes–corn–small grain–soybean resulted in 12.1 g C kg−1. There was a significant (P<0.05), quadratic cotton yield response (R2=0.54) to increasing SOC. Winter legume cover crops supplied between 90 and 170 kg N ha−1. Where no N has been applied in fertilizer or from a legume crop, annual N removal in the cotton crop is around 13 kg ha−1, about the same as that fixed in precipitation.

A study was conducted in Alabama to determine P removal by overland flow of swine lagoon effluent on bermudagrass (Cynodon dactylon L.'Russell') and annual ryegrass (Lolium multiflorum Lam), Treatments included ammonium nitrate at 560 kg N ha(-1) yr(-1), three rates of lagoon effluent which provided 560, 1120, and 2240 kg N ha(-1) yr(-1) and 71, 142, and 284 kg P ha(-1) yr(-1), respectively, and a control. Experiments were conducted at 5 and 10% slopes on a Marvyn loamy sand (fine-loamy, siliceous, thermic Typic Kanhapludults). The length of slope from application site do collection site was 6.1 m, Surface runoff was collected and sampled monthly for dissolved and sediment P, The results indicated that higher concentrations of P were found during the early spring and summer seasons when treatments were applied. Concentrations of dissolved P and total P exceeded critical values associated with accelerated eutrophication. No significant differences were found for sediment P concentrations on either 5 or 10% slopes for any of the three rates of P application, Phosphorus applications did not significantly affect dissolved P concentrations an the 5% slope, but there were significant treatment effects for dissolved P concentrations on the 10% slope, Slope did not significantly affect dissolved P concentration but significantly affected sediment P concentration, Total P mass losses in surface runoff were < 0.6 kg P ha(-1) on the 5% slope and 1.0 kg P ha(-1) on the 10% slope during the research period.

Most agricultural soils in the southeastern U.S. require periodic application of ground limestone in order to maintain productivity. Using boiler wood ash and combination ash as an alternative to ground limestone is agronomically productive, environmentally safe, and fiscally sound for both the ash producer and the landowner/farmer. While plant nutrient content of ash is variable, it should be,considered as an incidental source of plant nutrients, especially K and Mg, for field crops. An analysis of boiler ash from 14 Alabama pulp and paper mills averaged 38% CaCO3 equivalent (CCE) with a dry density of 500 kg m(-3). Although popular concerns are often expressed about land application of metals in boiler wood ash and in combination ash, levels are well within EPA's guidelines for land application of biosolids. There are no published reports of metals being an environmental or crop production/crop quality problem, especially when ash is used at recommended rates as a soil liming material. An analysis of the CCE along with a routine analysis of plant nutrients and selected total metals is needed to utilize ash as a soil amendment. If growers follow a conscientious soil testing program and apply ash as a liming material, some variability in the ash can be tolerated, especially at the rates generally used. Because boiler wood ash is considered a non-hazardous waste, it is regulated by individual states. Where it is being utilized as an agricultural lime or plant nutrient source or soil amendment, the state departments of agriculture regulate its licensing. Hauling and spreading can be a logistical problem because of the physical condition of ash and collection and handling practices by the generator. Nevertheless, research and experience from Maine to Alabama suggest that land application is a safe and practical approach to utilization of boiler wood ash and mixed ash by-products.

Swine (Sus scrofa) production requires economical and environmentally safe waste management systems, The objective of this study was to determine the effect of swine lagoon effluent on dry matter yield and N and P uptake of a mixture of hybrid bermudagrass [Cynodon dactylon (L.) Pers, cv. Russell] and annual ryegrass (Lolium multiflorum Lam,) grown on a Marvyn loamy sand (fine-loamy, kaolinitic. thermic Typic Kanhapludult). Treatments included a control with no nutrient additions, NH4NO3 at 560 kg N ha(-1) yr(-1), and swine lagoon effluent at 560, 1120, and 2240 kg N ha(-1) yr(-1). Effluent was applied using an overland now technique, The highest lagoon effluent rate added N at 4 times and P at 11 times the normally recommended rates for these forage grasses. Total dry matter yield was significantly increased by NH4NO3 and swine lagoon effluent additions, compared with the control treatment, Dry matter yield for the lowest effluent rate was not significantly different from that for the NH4NO3 treatment, and dry matter yields were not significantly different among the three rates of lagoon effluent. increasing the effluent rates generally increased total N and total P concentrations in the forage, Recoveries were about 32% for N and 20% for P at the lowest rate of lagoon effluent, and about 13% for N and 9% for P at the highest rate, The low recoveries of N and P with higher than recommended effluent rates could have environmental implications for the quality of soil, groundwater, and surface runoff.

The “Old Rotation” cotton experiment was designed to aid farm managers in implementing rotation schemes that not only increase yield, but also improve soil quality. Six different crop rotation treatments were imposed since 1896. Rotations were: IA, cotton (Gossypium hirsutum L.) grown every year without a winter legume and without N fertilization; IB, cotton grown every year with a winter legume and without N fertilization; IC, cotton grown every year without a winter legume and with 134 kg N as NH4NO3 ha-1 year-1; IIA, 2-year cotton-corn (Zea mays L.) rotation with a winter legume and without N fertilization; IIB, 2-year cotton-corn rotation with a winter legume and with 134 kg N ha-1 year-1 as NH4NO3; and III, 3-year cotton-corn- alternating soybean [Glycine max (L.) Merr.] or rye (Secale cereale L.) rotation with a winter legume and with 134 g N as NH4NO3 ha-1 year-1. Crimson clover (Trifolium incarnatum L.) was the winter legume cover crop. The 2-year cotton-corn rotation with a winter legume and with 134 kg N ha-1 year-1 (IIB) and the 3-year cotton-corn soybean/rye rotation with a winter legume and with 134 kg N ha-1 year-1 (III) had higher amounts of soil organic matter, soil microbial biomass C and crop yield than the other four treatments. The cotton grown every year without a winter legume or N fertilizer (IA) had a lower amount of soil organic matter, soil microbial biomass C and N and cotton seed yield than all other rotations. In 1988 and 1992 cotton seed and legume yield were correlated in positive, curvilinear relationships with soil organic matter (r2 ranged from 0.72 to 0.87). In most months, soil microbial biomass C and N was lower in the cotton grown every year without winter legumes or fertilizer (IA) than the other five rotations. In 1994, microbial biomass C and the Cmic:Corg ratio correlated in positive, curvilinear relationships with seed cotton yield (r2=0.87 and 0.98, respectively). After 99 years of management the “Old Rotation” cotton experiment indicates that winter legumes increase amounts of both C and N in soil, which ultimately contribute to higher cotton yields. Microbial biomass C and the Cmic:Corg ratio are poor predictors of annual crop yield but may be an accurate indicator of soil health and a good predictor of long-term crop yield.