Meaningful discussion that facilitates reflective thinking can be initiated when learners raise thoughtful questions or provide critical feedback; however, generating effective questions requires a certain level of domain knowledge and metacognitive skills of the question-askers. We propose a peer-questioning scaffolding framework intended to facilitate metacognition and learning through scaffolding effective peer-questioning in online discussion. This framework assumes that novice students who lack domain and metacognitive knowledge can be scaffolded to generate meaningful interactions at an early stage of learning and the resulting peer-generated adaptive questions can facilitate learners' metacognition. Thus, this study investigated the effects of providing online scaffolding for generating adaptive questions to peers during online small group discussion. A field experimental time-series control-group design was employed as a mixed model for the research design. Thirty-nine college students from an online introductory class on turfgrass management participated in the study. The findings revealed that the scaffolds were useful to increase the frequency of student questioning behavior during online discussion. For some students, the online guidance reportedly served as ''a starting point'' to generate questions when they had difficulty asking questions. However, the guidance did not improve the quality of questions and thus learning outcomes. The interview data indicated that peer-generated adaptive questions served a critical role in facilitating learner's reflection and knowledge reconstruction. Further study should focus on the quality improvement of peer-generated questions while considering adaptive and dynamic forms of scaffolding and intermediate factors such as prior knowledge, metacognition, task complexity, and scaffolding type.

Where a substantial thatch layer exists, new roots and stem growth from plant crowns occurs, at least initially, within the thatch. In some turfs, very little rooting may occur in the soil underlying the thatch. Therefore, under these conditions it appears that the thatch serves a greater role as a plant‐holding matrix and a growth medium while the soil's role decreases. The objective of this study was to determine the bulk density, total porosity, moisture characteristics, and organic matter contents of thatch and surface soils of thatched and thatch‐free Kentucky bluegrass (Poa pratensis L.) sites. The evaluation methods included: 1) the core method for measuring bulk density; 2) air pycnometric determination of total porosity; 3) a modified pressure plate procedure utilizing Tempe cells for determining moisture extraction curves; and 4) organic matter content on the basis of weight loss upon ignition. Bulk density of thatch was significantly lower than soil, but varied between thatch samples depending on the amount of soil within the thatch. Total porosity of thatch samples was not significantly different, but was greater than soil porosity. Moisture retention of thatch at low water potentials was less than the surface soil from thatch‐free sites, indicating that most of these pores are macro‐size pores. This study suggests that cultural practices, such as irrigation, may need to be modified to sustain aesthetic turf where thatch is a predominant component of the edaphic environment.

Nitrogen applied to turfgrass stands can be lost through leaching, denitrification, or ammnnia (NH)) 'olatilization. Tbe purpose of this in,estigation was to e,aluate tbe effects of N carrier and mode of application on NH) ,olatilization from a Kentucky bluegrass (POfl prfltensis L.)turf growing on an acidic (pH 6.4) Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) soil. The NH) wbicb 'olatilized after .application of any of senral sulfur-coated ureas (SCU), prilled urea, spray-applied solubilized urea, and two liquid N products was measured by passing tbe airstream from microecosystems, in whicb tbe treated turfs were growing, througb an indicating boric acid solution to trap NH). Ammonia-N losses after sulfur-coated urea fertilization ranged from 0.2% of tbe applied N wben tbe fertilization rate was 98 kg NI ba to 2.3 % of tbe applied N wben tbe fertilization rate was 293 kg NI ba. Wben prilled urea was applied at a rate of 293 kg N/ba, NH)losses averaged 10.3% of tbe applied N wbereas 4.6 and 1.6% of tbe applied N was lost after turf was fertilized witb 49 kg NIba from spray-applied solubilized urea and prilled urea, respectively. Ammonia losses from turf treated with liquid N sources ranged from 3.2 to 4.5% of the applied N. Tbe results of tbis researcb indicate tbat ammonia volatilization occurs to a limited extent in turfgrass stands growing on an acidic soil.

Thatch frequently exists as part of the edaphic environment of a turfgrass community and thus, should be considered when attempting to determine the fate of topically applied fertilizers in turf. The purpose of these investigations was to determine the influence of a thatch layer on the vertical mobility and transformation of soluble and slowly soluble N carriers following application. Measurements of N leaching, retention, and volatilization were made using cores of thatch and Flanagan silt loam (Aquic Argiudoll) soil extracted from fieldgrown turf of Kentucky bluegrass (Poa pratensis L.). Urea was selected as the soluble N carrier, and isobutylidene diurea (IBDU) was the slowly soluble N carrier. Application of urea resulted in 2.5 times as much N leaching and correspondingly lower N retention, in thatch than in soil. Where IBDU was used as the N source, leaching from the thatch was reduced from 81 to 5% of the applied N, and leaching from the soil was reduced from 32 to 23% compared to urea‐treated cores. In the volatilization studies, 39% of the applied N from urea was lost as ammonia from thatch cores compared to only 5% from the soil cores. Where IBDU was the N source, little N volatilization (4% from thatch, 2% from soil) occurred. In conclusion, where a substantial thatch layer exists, and turfgrass rooting is largely confined to the thatch layer, use of a slowly soluble N carrier might be preferable over soluble urea for reducing N losses due to leaching and volatilization. As an alternative, effective measures for controlling the thatch may result in greater efficiencies in the use of fertilizer N by the turfgrass community.