College of Agriculture & Natural Resources
Permanent URI for this communityhttp://hdl.handle.net/1903/1598
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
Browse
5 results
Search Results
Item Grain Marketing Outlook(2014-12-16) McNew, KevinDelivered at the the 2014 Policy and Outlook Conference by Kevin McNew covering the 2015 grain market outlookItem Trend-Adjusted Yield Option Introduced for Crop Insurance(Center for Agricultural and Natural Resource Policy, 2013-11-01) Goeringer, Paul; Lynch, LoriItem Nitrogen Management in Corn: Influences of Urea Ammonium Nitrate (UAN) Applications With and Without Nitrogen Stabilizer Products.(2013) Watkins, Patrick Howard; Kratochvil, Robert J; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Corn (Zea mays, L.) is a major crop produced in the nutrient sensitive Mid-Atlantic region. Nitrogen use efficiency (NUE) for corn is considered sub-optimal and farmers in the region use a number of best management practices (BMPs) to improve corn NUE. Two sidedress application methods (surface banding and sub-surface injection) and four commercially available nitrogen stabilizer products (`Agrotain', `Agrotain Plus', `Instinct', `Nutrisphere-N') were investigated during 2009-2011 over three N fertilizer rates at nine total locations. Headspace ammonia accumulation (post-sidedress) was indexed to the surface applied UAN treatment and resulted in application method and stabilizer products having a significant effect for headspace ammonia accumulations. Post-harvest inorganic soil nitrogen was not affected by application method or stabilizer products. Yield was not significantly affected by application method or stabilizer products but was affected by N rate. Total plant N concentration was not significantly affected by application method or stabilizer products.Item Corn Residual Nitrate and its Implications for Fall Nitrogen Management in Winter Wheat(2011) Forrestal, Patrick Joseph; Kratochvil, Robert J; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Corn (Zea mays, L.) production typically requires supplemental nitrogen (N) to optimize yields. In dryland corn production systems, where N is applied during the early to mid-vegetative growth stages, inappropriate N applications or limited moisture during the growing season can result in large disparities between optimum and applied N rates. This leads to variable post-harvest residual nitrate (NO3-N) accumulation, which is susceptible to loss. However, this NO3-N could provide the starter N requirement of the subsequent winter wheat (Triticum aestivum, L.) crop. Accounting for residual NO3-N present at wheat planting is important to avoid compounding N loss potential due to corn residual NO3-N accumulation. The objectives of this study were to 1) examine plant based tools for assessing soil NO3-N; 2) to examine post-harvest residual NO3-N accumulation patterns following corn production; 3) to determine optimum fall starter N rates for winter wheat production; and 4) to identify a soil NO3-N level above which starter N could be forgone without negative agronomic effect. This study found that plant canopy measurements are useful tools for assessing corn N management and for identifying drought sites, which had the greatest NO3-N accumulations. The corn stalk nitrate test was significantly (p<0.001) and positively correlated with soil residual NO3-N (r2=0.41). Greatest soil residual NO3-N accumulation occurred where drought conditions reduced production. The agronomic optimum fall starter N rate for winter wheat in Maryland is 17 to 34 kg N ha-1 where soil NO3-N concentration to 15 cm depth is less than 15 mg kg-1. However, the fall starter N response was highly variable and declined significantly (p<0.01) as fall precipitation after planting increased. The results of this study indicate that residual NO3-N levels at planting should be considered before applying fall starter N to winter wheat.Item Weed Suppression By Forage Radish Winter Cover Crops(2010) Lawley, Yvonne Elizabeth; Weil, Ray R; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Forage radish (Raphanus sativus L. var. longipinnatus) is a new winter cover crop in the Mid-Atlantic region. This study had three objectives: 1) to characterize the repeatability, amount, and duration of weed suppression during and after a fall-planted forage radish cover crop 2) to quantify its subsequent effect on direct seeded corn, and 3) to identify the mechanisms of this weed suppression. Forage radish cover crops were grown in ten site-years and followed by a corn crop in seven site-years in the coastal plain of Maryland. Forage radish was compared to rye (Secale cereale L.), oat (Avena sativa L.), and no cover crop treatments. Early and typical corn planting dates along with contrasting herbicide management strategies were compared over four site-years. Forage radish did not reduce population or yield in subsequent corn crops. Forage radish provided complete suppression of winter annual weeds in the fall and early spring but the suppression did not persist into the following cropping season. When forage radish cover crops were used in place of pre-plant burn down herbicide treatments to control weeds in early planted corn, some weeds were present at the time of corn emergence but corn yields were not reduced if emerged weeds were controlled with a postemergence herbicide. Controlled environment bioassays involving cover crop amended soil, aqueous plant extracts, and aqueous soil extracts along with a field experiment involving planted weed seeds did not provide evidence of allelopathy. In a residue moving experiment, no difference in spring weed suppression was observed if forage radish residues were removed prior to killing frost in November or left in place to decompose in three of four site-years. These results were supported by planting date experiments where fall ground cover and spring weed suppression was greatest for earlier planting dates of forage radish cover crops. Thus, rapid and competitive fall growth, rather than allelopathy, is the most likely mechanism of weed suppression by forage radish winter cover crop. Strategies to utilize the weed suppression of forage radish cover crops should focus on fall weed suppression and the early spring pre-plant window of weed control.