Although turfgrass fertilization influences many factors that affect turfgrass quality, little information is presently available that encompasses the interrelationships between fertilization, soil fertility, and turfgrass response and quality. A field study was conducted on Hagerstown soil (fine, mixed, mesic Typic Hapludalf) to determine the effects of N sources (Agrinite, Milorganite, ureaform, and urea), P rates (0, 0.49, 0.98, and 1.95 kg/100 m2), and K rates (0, 0.76, and 1.52 kg/100 m2) on soil nutrient levels and the growth, quality, and chemical composition of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) maintained as putting green turf. Wilting, disease, chlorosis, and annual bluegrass (Poa annua L.) infestation were used to assess quality. Fertilization with Milorganite increased available soil P and Mg. Available P and K in the soil ranged from 11 to 94 ppm and 0.06 to 0.28 meq/100 g, respectively. Elemental content of clippings was affected by all treatments, and treatment × date of sampling interactions that occurred could limit the usefulness of tissue analyses for diagnosing the nutritional status of turfgrasses. When K was applied at 0.76 kg/100 m2, both tissue and available soil K increased. When the K rate was increased to 1.52 kg/100 m2, the additional increment of K caused a greater increase in soil K and a smaller increase in tissue K than was obtained with the first increment of added K. The greatest change in tissue P occurred with the first incremental addition of P. Tissue P was not greatly affected by soil P above 24 ppm. Phosphorus fertilization had little effect on clipping yield; however, K fertilization tended to increase growth, as well as decrease chlorosis noted in early spring. Less severe summer wilting was observed with Agrinite, Milorganite, and K treatments. Less dollar spot (Sclerotinia homoecarpa F. T. Bennett) infection was noted with urea fertilization. Annual bluegrass invasion was favored by P and K fertilization and the effect of one was enhanced by the other. Milorganite, which increased soil P, also favored annual bluegrass. Results of this study indicated a need for more work in soil test calibration for turfgrasses.

Playing quality of athletic fields is critical to an athlete from the safety and performance standpoints. Use intensity and maintenance practices affect playing surface quality and impact characteristics within and among fields. The objective of this study was to quantitatively assess the effects of cutting height, compaction, soil water content (date), and turf cover on the impact absorption characteristics of Ken· tucky bluegrass (Poa pralensis L.) turf. Treatments were four cutting heights (0 [bare soil), 19, 38, and 57 mm), and two compaction levels (with and without) for Exp. I, and three cutting heights (19, 38, and 57 mm), two compaction levels, and three surface types (full turf, no verdure, and no thatch) in Exp. II. Surface impact characteristics measured were peak deceleration, time to peak deceleration, and im· pact duration. Two hammer weights, 2.25 kg and 0.5 kg, were used to assess impact characteristics on four dates and to obtain data for soil water conditions of0.263, 0.197, 0.163, and 0.064 kg kg-'. The highest peak deceleration values and shortest time periods were as· sociated with the periods of low soil water and compacted conditions. Only the 0.5-kg hammer detected differences in impact absorption characteristics between cutting heights. Significant cutting height-by· compaction-by-date interactions occurred for each impact characteristic, indicating interdependence of one of the factors on another. It appears that field management practices that influence soil water content, soil compaction, and turf cover are more important than cutting height in altering the impact absorption capability of Kentucky bluegrass turf.

Nitrogen sources with different properties and release characteristics are used to meet a variety of fertility management needs in turfgrass culture. Our objective was to determine the response of turfgrass to various urea‐formaldehyde reaction products; two particle sizes of oxamide; experimental sulfur‐coated ureas (SCU); products containing combinations of N sources; and an experimental composted sewage sludge. Nitrogen sources included for comparative purposes were isobutylidene diurea (IBDU); commercial SCU products; soluble sources; and Milorganite. In this 2.5‐yr study, 25 N source treatments were evaluated on ‘Merion’ Kentucky bluegrass (Poa pratensis L.) using 196 kg N ha−1 yr−1, split into two equal applications. Turf response was measured by weekly color ratings, weekly clipping yields, and N uptake for six growth periods during 2 yr. Urea‐formaldehyde reaction products containing no water‐in‐soluble N (WIN) gave results similar to those of conventional soluble N sources, while products containing WIN caused less initial color and growth responses, but gave a slight residual effect in the third year of use. Nitrogen uptake for powdered ureaform (66% of N as WIN) and the suspension FLUF (20% of N as WIN) was 44 and 75%, respectively, of that obtained with Formolene (0% WIN). Major differences in color and growth were found for the different particle sizes of oxamide, with the fine (<0.25 mm) material providing a faster release and less residual effect than the coarse (1‐3 mm) material. Turf fertilized with coarse oxamide responded similarly to that fertilized with coarse IBDU (0.7‐2.5 mm). Commercial SCU and fine particle SCU made with curtain granulated urea (94% of particles between 1.14 and 2.38 mm; dissolution rates: 6 and 15%) had pronounced residual effects, especially in the spring prior to fertilization. The experimental composted sewage sludge was inferior to Milorganite as a source of N for use on turf. N uptake with the compost treatment was only 32% of that obtained with Milorganite. Turf response from combinations of N sources generally reflected the amount and type of N source present. All N sources except the sludge compost were effective for turfgrass fertilization. Selection of an N source or combination of sources for turf fertilization should be dependent on quickness and duration of response desired, rate and frequency of applications, and various economic factors.

Synopsis Three grass species were grown in soil in which oxygen diffusion rates were varied by changing soil moisture tension and oxygen concentration. Root growth of Merion Kentucky bluegrass was greatly reduced or stopped in soil where oxygen diffusion rates were less than 5 to 9 × 1O−8g./cm.2/min. Penncross creeping bentgrass and goosegrass roots grew well at rates below 5 ✕ 10−8 g./cm.2Vmin. Nutrient accumulation was not appreciably decreased at low oxygen diffusion treatments.

Various slow‐release nitrogen sources were used to fertilize ‘Merion’ Kentucky bluegrass (Poa pratensis L.) for two growing seasons. Slow‐release sources were ureaform, activated sewage sludge, ADM (a coated urea), Urex (a urea‐paraffin product), and IBDU (isobutylidene diurea). Response to fertilization was measured by weekly determinations of clipping yield and color rating. Urex performed similarly to ADM, and response following application was quicker and greater than that from ureaform, sewage sludge, and IBDU. IBDU showed good controlled release characteristics, but initial response after fertilization was slow. Residual effects of IBDU gave green color earlier in the spring than other treatments. Nitrogen recovery in the clippings was determined. Recovery ranged from 54% for ADM to 22% for ureaform over the 2‐year period. Recovery from sewage sludge was 27%. The highest recoveries for IBDU and Urex treated plots were 46% and 52%, respectively. Recovery from a urea treatment was 52%.