No abstract

Late-season fertilization of bermudagrasses (Cynodon spp. L.C. Rich.) in the transition zone of the United States has traditionally been not recommended. This study was conducted to determine whether late-season fertilization could extend the duration of turfgrass color retention and visual quality without negatively impacting cold tolerance. Field plots of 'Midiron' and 'Tifway' bermudagrasses (C. dactylon 3 C. transvaalensis Burtt Davy), as well as 'Princess-77' and 'Riviera' bermudagrasses [C. dactylon (L.) Pers. var. dactylon] received applications of seaweed extract (SWE) (0.54 kg ha 21 ), N (49 kg ha 21 ), and Fe (1 kg ha 21 ) every 3 wk during the fall of 2001 and 2002.Visual turfgrass assessment showed that cultivar color ratings decreased as the fall progressed, with Princess-77 having greatest color retention in November of both years. Nitrogen was the only treatment to increase turfgrass color ratings relative to the control at the end of each growing season. Stolon samples removed from acclimated plants were artificially frozen to determine freezing tolerance. Midiron displayed the best freezing tolerance followed by Riviera, Tifway, and Princess-77. Chemical treatments did not have a significant effect on shoot regrowth from stolon nodes after freezing. In both years Midiron and Riviera displayed the quickest and greatest amount of spring greenup followed by Tifway and then Princess-77. Cold tolerance indicators proline and linolenic acid were highest in Midiron, followed by Riviera, Tifway, and Princess-77. Nitrogen, SWE, and Fe did not generally have an effect on linolenic acid and no consistent effects of these chemical treatments were noted on proline concentration. The results of this study indicate that judicious N applications during the fall can promote color retention and do not have a negative effect on bermudagrass cold tolerance.

Switchgrass (Panicum virgatum L.), a potential biofuel crop, can sequester soil organic carbon (SOC) and improve soil quality. However, its influence on soil aggregate mechanical properties controlling the macro-scale behavior of the whole soil needs to be assessed to understand processes that affect soil quality. This study assessed the impact of long-term (910 years) switchgrass, row crop, cool season grass pasture, and forest management on properties of soil aggregates for five ecosystems in the southeastern United States, including Blacksburg and Orange (VA), Knoxville (TN), Morgantown (WV), and Raleigh (NC). Relationships among aggregate properties were also determined. Tensile strength (TS), bulk density (D agg ), soil moisture retention (SMR), and SOC concentration of 1-to 8-mm aggregates were determined at the 0-to 10-cm and 10-to 20-cm soil depths. Management significantly affected the aggregate properties (P G 0.05), but the magnitude of the effects was site-dependent. The TS for switchgrass was the lowest (ı271 kPa) at all but the Blacksburg site for the 0-to 10-cm depth. The D agg for switchgrass was 10% lower at Blacksburg and 20% lower at Orange than that for row crop at the 0-to 10-cm depth. The SOC concentration for switchgrass was 2.5 times higher than that for row crop at Orange but not at Blacksburg. The TS increased with increasing D agg at Morgantown and Raleigh, but it decreased with increasing aggregate size at all sites. Aggregate size, D agg , and SOC were significant predictors of TS. Longterm switchgrass systems in the southeastern United States improve the aggregate strength properties, unlike row crop and cool season grass pastures, but their impact on SOC concentration is variable. (Soil Science 2005;170:998-1012)

No abstract

No abstract

It is generally accepted that plants closer to structures benefit from the warmth emitted via imperfect insulation and solar energy reemitted as long-wave, thermal radiation. However, while claims of protection are given, little quantifiable information exists on the extent or pattern of this protection. We studied existing plantings of Trachelospermum asiaticum, an evergreen groundcover that is frequently damaged in northeast Texas. The plantings studied were part of a landscape with at least five different identifiable microclimates: 1) near building (NB); 2) mid-bed (MB); 3) bed edge (BE); 4) beneath Quercus virginiana (LO); and 5) beneath Pyrus calleryana`Bradford' (BP). We placed HOBO temperature data loggers recording one temperature per minute in each location. Following our first damaging freeze, we waited 7 days before collecting leaf samples. Leaf samples were collected by using a 25-cm square, 2 cm deep on two sides. The square was placed on the groundcover so that the top of the groundcover was level with the top of the square. All leaves and stems that extruded through the top 2 cm of the square were excised. Four samples were taken from each location, and the number of damaged and nondamaged leaves were counted for each sample. Leaves that were at least 50% discolored were considered damaged. Leaf damage data were analyzed using SAS Proc ANOVA. Leaves in the BE and BP locations showed significantly fewer live leaves than any other locations. NB leaves were virtually undamaged. Average temperatures in the BE and BP locations were 4.5 to 5 °F colder than the “near building” locations, comparable to an a or b zone in the current USDA Plant Hardiness Zone map.