Michael D. Mullen

Phosphorus distribution and availability in response to dairy manure applications

Abstract As livestock operations become larger and concerns about water quality become greater, attention must be paid to the composition of animal manure and its potential impact on the environment. One current concern involves the amount and forms of phosphorus (P) being added to land with manure. The objective of this experiment was to determine the forms and availability of P in soils receiving 4 years of continuous dairy manure applications. Soil samples were collected from lysimeter plots established in 1991 to study the impact of dairy manure applications on surface water and groundwater. Soil P was fractionated into available (NaHCO3), iron (Fe)‐ and aluminum (Al)‐bound (NaOH), and calcium (Ca)‐bound (HC1) forms. These data were related to manure application rates, soluble P concentrations, and anion exchange membrane (AEM) bound P. Results indicate that the potential to move P by leaching through these loessial soils is very low even at high manure application rates. Large manure additions resulted in increases in all P forms; however, the inorganic pools increased more than the organic pools. The AEM values were a good tool for predicting potential P movement by soil erosion or runoff with membrane bound P being strongly correlated with manure application rate (r2=0.82) and available P (NaHCO3). Best management practices for manure disposal need to consider the potential for P movement through erosion and runoff, and the AEM technique provides a means for evaluating this potential.

Nitrogen budget for fescue pastures fertilized with broiler litter in major land resource areas of the southeastern US

The southeast US produces a tremendous number of broiler chickens (Gallus gallus), which in turn produce massive quantities of litter (manure and bedding materials). In the Southeast, litter is most often disposed of via land application to pastures, however, the ultimate fate of much of the applied nitrogen (N) is not known. We have constructed N budgets for three sites across the southeastern U.S. in an effort to determine how much of the applied N is useful for plant production and how much is left to be absorbed by the environment. Study sites were located in the Coastal Plain (Alabama), Piedmont (Georgia), and Cumberland Plateau (Tennessee) Major Land Resource Areas (MLRA) of the southeastern US. Litter was applied in the Spring of two consecutive years at a rate to supply 70 kg of available N ha−1. The total amount of N applied ranged from 103 to 252 kg N ha−1 depending on site and year. Nitrogen fluxes monitored in this study were broiler litter N, ammonia (NH3) volatilization, denitrification, plant uptake, and leaching. Plant uptake represented the largest flux of applied N, averaging 43% of applied N. Losses due to NH3 volatilization and denitrification combined were only 6% of applied N on average. Loss of N due to NO3-N leaching appeared to be significant only at the Coastal Plain site where NO3-N concentrations in the groundwater peaked at 38 mg N l−1. We believe the majority of excess N shown in these budgets is likely accounted for by leaching losses and soil accumulation. Regardless of these assumptions and low gaseous losses, it is apparent that on average, 57% of applied N is destined for a fate other than plant uptake. The results of this study indicate that land-application of broiler litter at currently recommended rates has the potential for negative impacts on the environment of the southeastern U.S. in the long-term.

Determination of 17b-estradiol Concentrations in Runoff from Plots Receiving Dairy Manure

Because of growing concern about estrogenic compounds in animal wastes, the objective of this research was to measure 17b-estradiol concentrations in runoff from plots fertilized with liquid dairy waste. Nine plots were established at The University of Tennessee Dairy Experiment Station located at Lewisburg, Tennessee, and dairy manure was applied to six of the nine plots. Three of the plots received manure at a rate sufficient to meet the nitrogen (N) requirement for winter wheat; three received manure at a rate sufficient to meet the phosphorus (P) requirement for winter wheat, and three received no manure. Runoff samples were collected after each of the first six runoff events producing natural rainfalls following manure application. Enzyme linked immunosorbant assays were used to determine the concentration of 17b-estradiol in the collected runoff samples. Preliminary results are reported herein, showing that 17b-estradiol concentrations in runoff from plots that historically received dairy manure, but which had not recently received manure, ranged from below detection threshold to 2.2 ng/L. In contrast, average 17b-estradiol concentrations in runoff from plots receiving manure at the N-rate were as high as 41 ng/L; plots receiving manure at the P-rate had average runoff 17b-estradiol concentrations as high as 29 ng/L. Runoff from both N and P treatments remained below the 100 ng/L level that we have taken to be biologically significant. Runoff concentrations from all plots decreased with time following application of manure.

Evaluating Solarization and Cultivated Fallow for Johnsongrass (Sorghum halepense) Control and Nitrogen Cycling on an Organic Farm

ABSTRACT A two-year field study evaluating efficacy of two weed control techniques on the noxious weed johnsongrass (Sorghum halepense L. Pers.) was conducted in Lexington KY. The weed control treatments were soil solarization, accomplished by covering the soil with clear plastic for 8 weeks, and cultivated bare fallow. Both treatments, along with a control treatment (mowing), were applied during the summers of 2003 and 2004 to a field heavily infested with johnsongrass (40–50% coverage). Effects of solarization on soil microbial activity and nitrogen (N) cycling were also evaluated. In both years, half of each treatment plot was lightly tilled 8 months after initial treatment application, and johnsongrass populations were characterized 2 months later. At the end of the experiment, the solarized-untilled treatment had lower johnsongrass populations than the cultivated-tilled and control treatments. Shallow tillage resulted in significantly more johnsongrass in the cultivated treatment in 2003, and in both cultivated and solarized treatments in 2004, compared with their untilled counterparts. At the conclusion of the experiment the johnsongrass populations were considerably reduced in both treatments compared with the original infestation. Solarization resulted in significant increases of both NH4-N and NO3-N in the soil during the time the plastic was in place, likely due to release of labile NH4-N from soil microbial biomass and subsequent nitrification. Substrate-induced respiration rates were also reduced during solarization, indicating a reduction of microbial biomass. However, these soil indicators were not persistent and should not prohibit the use of this weed management technique by organic growers.

Estrogen Concentrations in Dairy and Swine Waste Storage and Treatment Structures in and around Tennessee

Naturally occurring estrogens in animal wastes may cause negative environmental impacts in some watersheds. However, there is little published data regarding the concentrations of these estrogenic compounds in full-scale animal waste treatment and storage structures, thus making risk assessment difficult. To address this knowledge gap, the research described in this paper explores estrogen concentrations in 19 animal waste storage and treatment structures at dairy and swine production facilities in and around Tennessee. Samples have been collected from eight dairy and eleven swine facilities, representing a range of waste storage and treatment structures typical of Tennessee, and much of the southeastern US. The 17 â-estradiol concentrations in all samples have been assayed in triplicate serial dilutions by means of an enzyme linked immunosorbent assay (ELISA), all samples have, or will be, assayed for conventional manure constituents, including total solids, volatile solids, ash, total Kjeldahl nitrogen (TKN), total phosphorus, potassium, and chemical oxygen demand. Concentrations of 17 a-estradiol, 17 â-estradiol, and estrone are being assayed by gas-chromatography mass-spectroscopy (GC-MS), and total estrogenicity is periodically checked with a recombinant yeast reporter assay. At the time of this writing, the GC-MS dataset was incomplete, so that this paper is focused on the 17 â-estradiol ELISA data. Several tentative conclusions can be drawn from the preliminary data presented here, as follow: (1) 17 â-estradiol concentrations are highest in swine finishing hoop structure solids and swine farrowing pit slurry, with concentrations in excess of 20,000 ppt (parts per trillion) observed in both systems. Average 17 â-estradiol concentrations in swine farrowing and finishing lagoons were less than 4000 ppt. A similar trend was seen in dairy systems, where 17 â-estradiol concentrations in dry stacks averaged 10,000 ppt, while concentrations in lagoons and holding ponds were below 2000 ppt. (2) The mass-ratio of 17 â-estradiol to TKN followed a different trend than did the raw 17 â-estradiol concentrations. For example, swine farrowing lagoons had the greatest ratio (ca. 25 ppm), while swine fishing hoop structure solids and swine farrowing pit slurries had ratios four times smaller. We believe that the mass-ratio of 17 â-estradiol to application-rate-limiting macronutrients is a better predictor of the estrogen emission risk than is the raw 17 â-estradiol concentration in the waste. (3) There is spatial heterogeneity in 17 â-estradiol distribution within most structures studied. In 9 of the 11 liquid systems studied, a positive correlation was observed between 17 â-estradiol and depth; in dry-stack dairy systems, older parts of the stack had lower 17 â-estradiol concentrations than did newer parts of the stack.