Influence of Nitrogen Addition and Plant Root Parameters on Phytoremediation of Pyrene-contaminated Soil

Phytoremediation is a method in which plants, soil microorganisms, amendments, and agronomic techniques interact to enhance contaminant degradation. We hypothesized that bermudagrass (Cynodon dactylon L) and an appropriate amount of N fertilizer would improve remediation of pyrene-contaminated Captina silt loam soil. The soil was contaminated with 0 or 1,000 mg pyrene/kg of soil and amended with urea at pyrene-C:urea-N (C:N) ratios of 4.5:1, 9:1, 18:1, or unamended (36:1). Either zero, one, two, or three bermudagrass sprigs were planted per pot and ?33 kPa moisture potential was maintained. Pyrene concentrations, inorganic-N levels, shoot and root parameters, and pyrene degrader microbial numbers were measured following a 100-day greenhouse study. At a C:N ratio of 4.5:1, the presence of plants increased pyrene biodegradation from 31% for the no plant treatment to a mean of 62% for the one, two, and three plant treatments. With no plants and C:N ratios of 4.5:1, 9:1, 18:1, and 36:1, the mean pyrene biodegradation was 31, 52, 77, and 88%, respectively, indicating that increased inorganic-N concentration in the soil reduced pyrene degradation in the treatments without plants. Additionally, none of the one, two, or three plant treatments at any of the C:N ratios were different with a mean pyrene degradation value of 69% after 100 days. Pyrene resulted in reduced shoot and root biomass, root length, and root surface area, but increased root diameter. The pyrene degrading microbial numbers were approximately 10,000-fold higher in the pyrene-contaminated soil compared to the control. At the highest N rate, bermudagrass increased pyrene degradation compared to the no plant treatment, however, in the unvegetated treatment pyrene degradation was reduced with added N.     

Integrated control of grape black rot: influence of host phenology, inoculum availability, sanitation, and spray timing

ABSTRACT The epidemiology and control of black rot (Guignardia bidwellii) was studied from 1995 to 1999 in vineyards in Dresden and Naples, NY, where disease pressure was moderate and extreme, respectively. The efficacy of serial applications of myclobutanil, provided at 2-week intervals and varied with respect to their number and time of initiation, was examined within the context of host phenology, inoculum availability, and sanitation. At Dresden, sprays applied over 4 weeks through the immediate prebloom stage provided only 13 to 91% control of diseased clusters, despite the release of 95% of the season's ascosporic inoculum during the period of fungicidal protection. However, applications immediately prior to bloom plus 2 and 4 weeks later, which afforded protection while fruit are highly susceptible to infection, provided virtually complete control. At Naples, where mummified berries were retained in the canopy after mechanical pruning, this same regime provided only approximately 80% disease control, but applying a fourth spray 2 weeks prebloom generally improved control. Hand-pruning mummies to the ground in selected plots significantly (P 相似文献