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...

Buffalograss [Buchloë dactyloides (Nutt.) Engelm.] is a turfgrass species with reduced irrigation and fertilization requirements, relative to traditional turfgrasses. Interest in reducing the amount of chemicals and water applied to turfgrass has resulted in increased efforts to improve buffalograss as a turfgrass. As interest in using the new turf‐type buffalograss cultivars has increased, the need for nitrogen rate and mowing height recommendations supported by research have become necessary. ‘Cody’, ‘Texoka’, ‘378’, and ‘NE 91‐118’ buffalograss cultivars were planted at sites located in Nebraska, Kansas, and Utah to determine nitrogen rate and mowing height effects on buffalograss quality, color, density, and clipping yield. There were significant cultivar × nitrogen rate interactions at all sites for quality, color, and density. Regardless of cultivar, nitrogen rate × year interactions at all sites revealed that the 98 kg N ha−1 rate sustained quality, color, and density over the 3‐yr evaluation period, while lower nitrogen rates had decreased quality, color, and density. The 195 kg N ha−1 rate improved quality over the 3‐yr period but also had the highest clipping yields. Regardless of the cultivar selected, the data support the general mowing height recommendation for turf‐type buffalograss of 5.0 to 7.5 cm. For golf course fairways maintained at a mowing height of 2.5 cm, the vegetatively established cultivars (NE 91‐118 and 378) are the best choice to achieve high turfgrass quality.

Tolerance to soybean cyst nematode (SCN), Heterodera glycines Ichinohe, has been identified in soybean [Glycine max (L.) Merr.] and has potential as a management strategy to limit SCN yield suppression. Little information is available on the growth and morphology of roots of tolerant soybean cultivars parasitized by SCN. This study was conducted to compare root and vegetative responses of a moderately tolerant soybean, ‘Wright’, with an intolerant soybean, ‘Bragg’, to parasitism by SCN. In 1986, Bragg and Wright soybean was grown in the University of Georgia rhizotron in rooting medium infested with SCN Race 3 at initial population densities (Pi) of 0, 1000, or 10 000 eggs/L. Measurements were made of soybean root growth and development, vegetative and reproductive growth stage, leaf number, flower and pod numbers, and nematode activity (development and infection). Number of growing roots on Bragg at Pi 10 000 was suppressed throughout the season, whereas root growth of Wright was stimulated by the presence of SCN. Although not statistically significant, root lengths followed these same trends. Seed yield of Bragg was progressively suppressed as Pi increased, in contrast to that of Wright which was suppressed at Pi 1000, but was not suppressed further at Pi 10 000. Vegetative development of Bragg was suppressed at Pi 10 000 compared to Pi 0 from 18 and 39 d after planting (DAP), respectively, in contrast to Wright which was unaffected. Reproductive development of Bragg at Pi 10 000 was also suppressed between 79 and 133 DAP. The stimulation of root development of Wright in the presence of SCN was probably critical to maintenance of vegetative and reproductive development.