Foliar fertilization often comprises a significant portion of the total annuai N appiied to putting greens. This study was initiated to evaluate the efficiency of this practice under field conditions. '^N-iabeied urea was used to quantify seasonal uptake of foliar-applied N by creeping bentgrass {Agrostis stolonifera var. L. palustris (Huds.) Farw. 'Penn AT) and hybrid bermudagrass {Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt Davy Tifeagle') managed as putting greens. Urea was spray-applied monthly. May through September, at rates of 0.5 and 1.25 g N m"^. Both species absorbed urea rapidly, with 24 to 67% of the fertilizer N entering the foliage within 1 h following treatment; peak foliar absorption was generally observed at 4 h after treatment. Percentage of foliar uptake was significantly reduced at higher application rates for both species. In addition, absorption of urea-N by foiiage of both species was affected by month of application and year. When averaged across all sampling times and N rates, foliar absorption percentages were similar between the two species, ranging from 36 to 69% for creeping bentgrass and 38 to 62% for bermudagrass. Overall, foiiar absorption efficiency was variable and there were no consistent seasonal trends associated with these differences.

Foliar N fertilization often makes up a major portion of the total N inputs applied to creeping bentgrass (Agrostis stolonifera L.) golf greens. Many such applications are made using fertilizers that have been formulated and marketed as specialty foliar fertilizers. Various forms of inorganic and organic N are included in these specialty products. However, little is currently known about the foliar absorption efficiency among different chemical N forms routinely applied to putting greens. This project was conducted to evaluate the foliar uptake of N from several 15N‐labeled inorganic and organic sources. Three common N fertilizer forms {urea (NH2CONH2), ammonium sulfate [(NH4)2SO4], and potassium nitrate (KNO3)} were used in the trial along with three amino acids (glycine, l‐glutamic acid, and l‐proline). All treatments were applied at a rate of 0.5 g N m⁻2 on 18 Sept. 2008, 14 Oct. 2008, and 24 June 2010 to plots within a ‘Penn G2’ creeping bentgrass research green. Plant tissue samples were taken 1 and 8 h after application for N analysis. Foliar uptake of the various N compounds ranged from 31 to 56% of the N applied at the final sampling time of 8 h after application. Nitrogen source had a significant effect on the amount of N fertilizer recovered within plant leaves and shoots. Foliar absorption of KNO3 into aerial plant parts was lower than most of the chemical forms tested while most of the compounds supplied N to the plant in similar proportions.

Dafa are lacking in the quantification of N loss mechanisms associated with foliar fertilizer applications thaf are common to golf course and putting green turfgrass management. This study was conducted to measure ammonia (NHg) volatilization after application of foliar N (as urea) to creeping bentgrass [Agrostis stolonifera L. var. paiustris (Huds.) Farw. cv. Penn AI] and hybrid bermudagrass [Cynodon dactyion (L.) Pers. x C. transvaaiensis Burtt Davy cv. Tifeagle] putting greens in Fayetteville, AR. Urea was spray-applied monthly. May through September, at rates of 0.5 and 1.25 g N m"^. Ammonia (NH3) volatilization, over a 24 h period, was measured via boric acid trapping within closed, static diffusion chambers. Month of year and N rate significantly affected the amount of N volatilized from the turfgrass canopy. Measured NH3 volatilization was consistently low each year for both species, with average annual NH3 volatilization of 0.35% and 2.55% from creeping bentgrass and hybrid bermudagrass, respectively. A trapping efficiency study was conducted and revealed that 35 to 50% of evolved NH3-N was directly absorbed by plant tissue enclosed within the chambers. While it was determined that the NH3 trapping methodology used here could not account for all of the NH3 volatilized, data from this study does support the conclusion that foliar N (as urea) applications to putting green turf can be made to actively growing plant tissue throughout the season without concern for substantial N loss via NH3 volatilization.

Annual bluegrass (Poa annua L.) is the most common weed in creeping bentgrass (Agrostis stolonifera L.) putting greens and is especially competitive in shade. The objectives of this study were to determine if foliar magnesium plus foliar iron applications, alone and in combination with activity enhancers, were effective for suppressing indigenous annual bluegrass in shaded and full‐sun creeping bentgrass putting greens. Multi‐year field studies were conducted in three locations. A linear contrast between plots receiving Mg/Fe and plots not receiving Mg/Fe indicated that Mg/Fe applications caused an increase in annual bluegrass proportion in a mixed sward of creeping bentgrass and annual bluegrass in shade but had no significant effect in full sun. The research suggested that using Mg/Fe to enhance chlorophyll synthesis in shade favored the most phytosynthetically efficient species, annual bluegrass, in a mixed stand of turf. According to these results, Mg/Fe applications in shade are advisable for turf managers who wish to improve annual bluegrass persistence but not for those who would like to reduce annual bluegrass populations. Applications of Mg/Fe had no effect on annual bluegrass populations in full sun.

The Illinois soil N test (ISNT) is intended to predict the amount of mineralizable N in a soil by estimating the amount of amino sugar N present. The objective of this study was to compare the ISNT with a direct steam distillation (DSD) method for recovering ^^N-labeled glucosamine added to soil collected from the 0-to 15-, 15-to 30-, 30-to 45-, and 45-to 60-cm depth increments. Four clay and four silt loam soils where chosen from rice (Oryza Sativa L.) production regions in the mid-South United States. When the ISNT and DSD were compared across all soils and for all depths, the N liberated with the DSD was, on average, 19.2 mg N kg~^ soil greater than the N liberated with tbe ISNT. The ISNT recovered 89.2 to 97.9% and the DSD method 88.5 to 99.1% of the ^^N-glucosamine added to the four soil deptb increments for all eight soils. There was a significant interaction between soil depth and method; the ISNT recovered a greater amount of added glucosamine-N from the 0-to 15-cm depth tban the DSD. Overall, the ISNT and the DSD methods recovered similar amounts of added glucosamine N from each soil depth below 15 cm but alkaline hydrolyzable N (AH-N) and total N (TN) appear to influence tbe recovery of glucosamine when using the DSD. The results of tbis study indicate tbat the ISNT and DSD methods can recover similar amounts of glucosamine N in soils with different textures; however, the glucosamine N recovery by DSD is highly influenced by the presence of AH-N, as indicated by a significant negative relationship.Abbreviations: AH-N, alkaline hydrolyzable nitrogen; DSD, direct steam distilliition; ISNT, Illinois soil nitrogen test;TN, total nitrogen.