@article{ritchey_tyler_essington_mullen_saxton_2015, title={Nitrogen Rate, Cover Crop, and Tillage Practice Alter Soil Chemical Properties}, volume={107}, ISSN={["1435-0645"]}, DOI={10.2134/agronj14.0226}, abstractNote={Long‐term management practices can influence many physical and chemical soil properties. This study investigated the influence of 14 yr of continuous cotton (Gossypium hirsutum L.) management systems on soil pH, soil organic C (SOC), and exchangeable cations. Management practices consisted of varying N rate, tillage (no‐tillage [NT] or disk tillage [DT]), and cover crop on a Lexington silt loam soil (Ultic Hapludalf) in the absence of lime additions. Lower soil pH was present in NT, hairy vetch (Vicia villosa L.) cover treatments and with increasing N rate but similar between 0‐ to 7.5‐ and 0‐ to 15‐cm sample depths. Soil pH decreased between 0.23 to 0.37 units for each 34 kg N ha−1 added and 0.46 units with hairy vetch cover. Hairy vetch cover and 101 kg N ha−1 resulted in pH <5 and increased SOC and exchangeable Mn. Exchangeable Al values were >0.30 cmolc kg−1 with 101 kg N ha−1 and hairy vetch cover and with 101 kg N ha−1 under NT, but they were ≤0.13 cmolc kg−1 for all other treatments. Exchangeable Al increased at pH <5 for NT with hairy vetch cover, while changes were insignificant for all other treatments. The hairy vetch cover contributed acidity equivalent to 42 to 68 kg N ha−1 as NH4NO3. Although stratification of SOC occurred under NT, no other measured properties varied with depth in NT treatments, and different recommendations are not necessary for NT crop production. Appropriate N credits from hairy vetch cover will reduce excessive acidity, production costs, and potential environmental concerns.}, number={4}, journal={AGRONOMY JOURNAL}, author={Ritchey, Edwin L. and Tyler, Donald D. and Essington, Michael E. and Mullen, Michael D. and Saxton, Arnold M.}, year={2015}, pages={1259–1268} }
 @article{law_bhavsar_snyder_mullen_williams_2008, title={Evaluating Solarization and Cultivated Fallow for Johnsongrass (Sorghum halepense) Control and Nitrogen Cycling on an Organic Farm}, volume={26}, ISSN={0144-8765 2165-0616}, url={http://dx.doi.org/10.1080/01448765.2008.9755079}, DOI={10.1080/01448765.2008.9755079}, abstractNote={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.}, number={2}, journal={Biological Agriculture & Horticulture}, publisher={Informa UK Limited}, author={Law, Derek M. and Bhavsar, Victoria and Snyder, John and Mullen, Michael D. and Williams, Mark}, year={2008}, month={Jan}, pages={175–191} }
 @article{devine_tyler_mullen_houston_joslin_hodges_tolbert_walsh_2006, title={Conversion from an American sycamore (Platanus occidentalis L.) biomass crop to a no-till corn (Zea mays L.) system: Crop yields and management implications}, volume={87}, ISSN={0167-1987}, url={http://dx.doi.org/10.1016/j.still.2005.03.006}, DOI={10.1016/j.still.2005.03.006}, abstractNote={It is not known if a short-rotation woody crop (SRWC) grown on a historically agricultural site will affect subsequent row crops if the site is returned to annual row crop production after harvest of the SRWC. The objectives of this study were to determine the feasibility of converting an American sycamore biomass plantation to a no-till corn system and to document the effects of the sycamore plantation on corn grain yields and N fertilizer efficacy. The study was in southwestern TN, USA, on a Memphis–Loring silt loam intergrade (fine-silty, mixed, active, thermic Typic Hapludalfs—fine-silty, mixed, active, thermic Oxyaquic Fragiudalfs). Four-year (SY4C) and 5-year (SY5C) rotations of American sycamore were followed by no-till corn. Soybean [Glycine max (L.) Merr.] followed by corn (SBC) was a control treatment. Four rates of broadcast NH4NO3 (0, 73, 146, and 219 kg N ha−1) were applied to corn crops. The quantity of N removed in the harvest of the sycamore crop was similar to that of a single harvest of corn grain; thus, the SRWC did not constitute a significant loss of N from the system. No mechanical problems were encountered when planting no-till corn over sycamore stumps. Stump total N concentration increased from 2.2 to 8.5 g kg−1 in the first 104 weeks after sycamore harvest, likely due to microbial immobilization. While first- and second-year corn after sycamore required 219 kg ha−1 fertilizer N to maximize grain yield, third-year corn after sycamore and corn grown after soybean both reached maximum yields at 146 kg N ha−1. These responses suggest that the N fertilizer requirement during at least the first 2 years of corn following sycamore is increased by the sycamore crop. After converting from a SRWC to a row crop, plant-available N should be carefully monitored due to potential losses from N immobilization in woody residues.}, number={1}, journal={Soil and Tillage Research}, publisher={Elsevier BV}, author={Devine, Warren D. and Tyler, Donald D. and Mullen, Michael D. and Houston, Allan E. and Joslin, John D. and Hodges, Donald G. and Tolbert, Virginia R. and Walsh, Marie E.}, year={2006}, month={May}, pages={101–111} }
 @article{raman_williams_layton_burns_easter_daugherty_mullen_sayler_2004, title={Estrogen Content of Dairy and Swine Wastes}, volume={38}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es0353208}, DOI={10.1021/es0353208}, abstractNote={Naturally occurring estrogens in animal wastes may cause negative environmental impacts, yet their abundance in animal waste treatment and storage structures is poorly documented. To better quantify estrogen concentrations in animal wastes, multiple waste samples were collected from treatment and storage structures at dairy and swine facilities and analyzed for concentrations of 17beta-estradiol (E2), estrone (E1), and 17alpha-estradiol by gas chromatography-mass spectroscopy and by enzyme linked immunosorbent assay (E2 only). Mass ratios of each estrogen to the macronutrients nitrogen, phosphorus, and potassium were also determined. Because manure application rates are typically macronutrient-based, estrogen to macronutrient ratios are proportional to areal mass application rates of estrogen to fields. Swine farrowing waste (from farrowing sows and piglets) had the highest ratios of E2 to macronutrients. Mean ratios in swine farrowing waste were roughly twice those in swine finishing waste (from growing male and nonpregnant female animals) and more than four times higher than those in dairy waste (from lactating cows in various stages of their reproductive cycles); these differences were statistically significant (alpha = 0.05). Estrone followed a similar trend. In contrast, ratios of 17alpha-estradiol to macronutrients were highest in dairy operations. These results can be used to better predict estrogen loading rates on fields receiving swine and dairy wastes.}, number={13}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Raman, D. Raj and Williams, Elizabeth L. and Layton, Alice C. and Burns, Robert T. and Easter, James P. and Daugherty, Adam S. and Mullen, Michael D. and Sayler, Gary S.}, year={2004}, month={Jul}, pages={3567–3573} }