The fate of urea applied to Kentucky bluegrass (Poa pratensis L.) turf was studied over a 2-yr period using a combination of intact monolith lysimeters and small plots. Soil type was a Marlette fine sandy loam (fine-loamy, mixed mesic Glossoboric Hapludalfs). Urea was applied at a rate of 196 kg N ha-~ yr-~ in five equal applications of 39.2 kg N ha-i, using two application schedules. Treatments were fertilized at approximately 38-d intervals with the "Spring" treatment fertilized from late April through late September and the "Fall" treatment from early June through early November. In 1991 only, the April and November applications used tSN-labeled urea (LFN). For the Spring treatment, 31% of LFN was recovered from thatch at 18 DAT. This value remained constant for the next year, then gradually declined to 20% after 2 yr. Only 8% of the LFN was recovered from soil at 18 DAT and increased to only 20% 2 yr after application. Approximately 35% of the LFN was harvested in clippings over 2 yr. Through May 1993 (748 DAT), LFN in leachate totaled 0.18% of the amount applied. For the Fall treatment, 62% of the LFN was recovered from thatch at 18 DAT. This value declined to 35% by the following June. LFN in soil increased from 12% to25% over 2 yr. Approximately 38% of the LFN was harvested in clippings over 2 yr. Total leachate LFN recovery was 0.23% over the 2-yr period. Total recovery of LFN was 64 and 81% for the Spring and Fall treatments, respectively, suggesting volatile losses of N. Whether the N was applied in the spring or late fall, rapid uptake and immobilization of the LFN resulted. A maximum of 25% of applied LFN was recovered in the soil from either application timing at any time over the 2 yr of the experiment. A well-maintained turf intercepts and immobilizes LFN quickly making leaching an unlikely avenue of N loss from a turf system. L TE FALL (early to mid-November) N fertilization cool season turf has been recommended for many years. Wilkinson and Duff (1972) induce a growth or color response through the winter, but plants had higher chlorophyll contents and enhanced growth and color in mid-April compared with plants fertilized earlier in the Fall. These characteristics are desirable in turfgrass culture. However, leaching of fertilizer nitrogen (FN) applied to turf has received much attention in recent years, and the fate of late fall N applications may be of special concern due to slow growth rates and potential lack of plant uptake.Studies of N fate under turf management conditions are limited; however, investigations into certain aspects of N fate such as leaching or plant uptake are more plentiful and have recently been reviewed by Petrovic (1990). Starr and DeRoo (1981), using a Kentucky bluegrass-red fescue (Festuca rubra L.) turf, observed that where clippings were not returned, total N removed during mowing averaged 95 kg ha -~ yr -~ over three years, equivalent to 50% of the FN applied. Where clippings were returned, harvested N averaged 137 kg ha -~ yr -~ (73% of applied FN). By u...

Annual bluegrass (Poa annua var. reptans (Hausskn.) Timm.) is a weedy species that is a component of most close‐cut, irrigated fairways. Research was conducted to determine the effect of five management factors and their interactions on the species composition of a mixed stand of annual bluegrass and creeping bentgrass (Agrostis palustris Huds.) maintained at 13 mm. Soil was an Owosso‐Marlette sandy loam (fine‐loamy, mixed, mesic, Typic and Glossoboric Hapludalfs). Management factors investigated for 3 yr were irrigation (daily at 75% open pan evaporation (OPE), triweekly at 110% OPE, and at wilt); clipping treatments (returned or removed); N fertility (98 or 293 kg N ha−1 yr−1); plant growth regulator (PGR) treatments (mefluidide, N‐[2,4‐dimethyl‐5‐[[(trifluoromethyl)‐sulfonyl] amino] phenyl] acetamide, at 0.14 kg ha−1; EL‐500, α‐(1‐methylethyl)‐α‐[4‐(trifluoromethoxy)phenyl] 5‐pyrimidine methanol, at 1.12 kg ha−1 and a control) and ‘Penncross’ creeping bentgrass overseeded (49 kg ha−1 yr−1) or not overseeded). Changes in annual bluegrass (AB) populations for each growing season were determined utilizing the point quadrat method. The effect of clipping removal on AB seed in the soil was determined. Returning clippings increased annual bluegrass 12% over plots in which clippings were removed. Overseeding with creeping bentgrass (CB) increased CB populations 8% compared to plots irrigated daily at 75% OPE and not overseeded. Mefluidide in combination with high N fertility resulted in AB populations 8% higher than control or EL‐500 plots at the same fertility level. Mefluidide also increased AB populations relative to control or EL‐500 treatments when clippings were removed. The greatest significant decrease in AB (28%) occurred with the treatment combination of clippings removed, overseeded, and no PGR. Removing clippings reduced the number of viable AB seeds in the soil by 60%.

The biosynthesis of fumonisin B1 by Fusarium moniliforme was studied in liquid culture. Stable isotope labeled alanine was added as a precursor to static and shaken cultures of F. moniliforme. Incorporation of 13C and 2H labeled L-alanine into fumonisin B1 was measured by GC-MS. Under static culture conditions, 20.8 micrograms ml-1 of FB1 were produced with a 5.5% level of incorporation of intact, labeled alanine into fumonisin B1. Under shake culture conditions, much higher levels of fumonisin B1 were produced with levels reaching 159-240 micrograms ml-1 by 21 days after culture initiation. A lower level of alanine incorporation, from 1.1-1.4%, was observed under these conditions. Under shake conditions, incorporation of labeled alanine was reduced because of the rapid metabolism of these cultures combined with the high level of fumonisin B1 production resulted in rapid turnover of the added, labeled alanine and reduced percentage of incorporation. The evidence presented indicates that alanine is incorporated intact into fumonisin B1.

Low‐input sustainable turf (LIST) management represents a resource‐efficient option in maintaining uniform, persistent turf. What species are best suited to such management needs to be established. To this end, 12 hardy species were evaluated for 3 yr in Illinois, Indiana, Iowa, Michigan, Missouri, Ohio, and Wisconsin: crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult. ‘Fairway’, ‘Ephraim’, and ‘Ruff’], streambank wheatgrass [Agropyron riparium Scribn. & Smith ‘Sodar’; syn. Elymus lanceolatus (Scribn. & J.G. Smith) Gould subsp. lanceolatus], Canada bluegrass (Poa compressa L. ‘Reubens’), hard fescue [Festuca ovina var. duriuscula (L.) Koch ‘Durar’; syn. F. lemanii T. Bastard], sheep fescue (F. ovina L. ‘Covar’ and common), tall fescue (F. arundinacea Schreb. ‘Alta’), bulbous bluegrass (P. bulbosa L.), alpine bluegrass (P. alpina L.), redtop (Agrostis alba L. ‘Reton’; Agrostis gigantea Roth), roughstalk bluegrass (P. trivialis L. ‘Colt’), colonial bentgrass (Agrostis tenuis Sibth. ‘Exeter’; syn. Agrostis capillaris L.), and buffalograss [Buchlöe dactyhides (Nutt.) Engelm. ‘Texoka’ and ‘NE‐315’]. AH were field‐established and compared at three mowing heights: 3.8 cm, 7.6 cm, and no mowing. Quality ratings were based on uniform persistence. Tall fescue and common sheep fescue were the best and most broadly adapted to LIST. In Iowa, hard fescue, Canada bluegrass, and crested wheatgrass also did well. Colonial bentgrass was best adapted in Missouri. Redtop and roughstalk bluegrass grew better in a north‐south area from Wisconsin through central Illinois to Missouri. The buffalograsses excelled in Ohio and southern Illinois. Over all species, the 7.6‐cm mowing height allowed the best turf quality. Specifically, tall fescue, colonial bentgrass, redtop, and common sheep fescue performed best at the 7.6‐cm mowing height. Covar sheep fescue, hard fescue, Canada bluegrass, and Fairway crested wheatgrass could not maintain persistent stands under the 3.8‐cm mowing height. No mowing resulted in intermediate levels of quality with all species. A 7.6‐cm mowing height would be appropriate for testing species in LIST within the seven‐state region used in this study.

Pers.], and 'Tifway' bermudagrass [C. dactylon (L.) Pers. ϫ C. transvaalensis Burtt-Davy] (Johnson, 1992).Reducing turfgrass clipping production is often the goal of manag-Repeated monthly applications of TE to a mixed stand ers who recognize the need to save time, money, or landfill space. The objective of this study was to investigate the long-term implications of of colonial bentgrass (Agrostis tenuis Sibth.), highland repeated trinexapac-ethyl [4-(cyclopropyl-␣-hydroxy-methylene)-3, bentgrass (A. castellana L.), and fine fescue (Festuca 5-dioxocyclohexanecarboxylic acid ethyl ester] applications at two rubra L.) had minimal toxicity and reduced shoot fertility levels (150 and 300 kg N ha Ϫ1 yr Ϫ1 ) on Kentucky bluegrass growth by more than 40% (Daniels and Sugden, 1996), (Poa pratensis L.). Trinexapac-ethyl (TE) was applied at 0.17, 0.23, with clippings collected monthly for three consecutive or 0.29 kg a.i. ha Ϫ1 every 4 wk or at 0.23, 0.29, or 0.34 kg a.i. ha Ϫ1months. Up to 40% clipping reduction was also obevery 6 wk for three growing seasons. Clippings were reduced by 22Abbreviations: TE, trinexapac-ethyl. Published in Agron.