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Turf managers apply plant growth regulators (PGRs) throughout the growing season to reduce clipping production, provide a uniform canopy, and increase color. Reduced efficacy of trinexapac-ethyl (TE) [4-(cyclopropyl-[alpha]-hydroxy-methylene)-3, 5-dioxocyclohexanecarboxylic acid ethyl ester] and paclobutrazol (PAC) [(2RS, 3RS)-1(4-chlorophenyl)-4, 4-dimethyl-2-(1H-1,2,4-tri-azol-1-yl) pentan-3-ol] has been reported during warmer summer months. Plant growth regulator dissipation and Kentucky bluegrass (KBG; Poa pratensis L.) clipping production, canopy leaf area, and carbon exchange rates (CERs) were measured following single TE or PAC applications applied at three rates and three application timings. Warmer summer conditions reduced the intensity and duration of TE and PAC growth suppression compared to spring applications. Plant growth regulator applications above the manufacturers label rate provided no additional suppression. Residues of PGRs were analyzed by HPLC-UV. Warmer temperatures increased TE and PAC uptake, but accelerated the rate of PGR dissipation. Carbon exchange rates were measured weekly on ground (CERG) and leaf (CERL) area bases. Treatment with PGRs resulted in decreased leaf area early during inhibition followed by increased rate of leaf area production. Changes in canopy leaf area were greatest in spring and PAC caused the greatest change in leaf area. Changes in CERG reflected changes in leaf area. Paclobutrazol generally increased CERL during periods of clipping suppression, while TE had no effect on CERL.

Trinexapac-ethyi (TE) [4-(cyclopropyl-[alpha]-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] and paclobutrazol (PAC) [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1, 2,4-triazol-l-yl)pentan-3-ol] are routinely used to suppress clipping production. Single-leaf turfgrass C exchange rates (CERs) in response to plant growth regulator (PGR) treatment have not been characterized. Individual Kentucky bluegrass (KBG, Poa pratensis L.) plants received label rates of TE or PAC and were placed in growth chambers at 23/18 or 30/25[degrees]C. Photosynthetic efficiency and CER measurements were recorded every 4 d for 44 d. Total root length (TRL), root surface area (SA), and average root diameter were measured at the end of the study. Reductions in CERs of TE- or PAC-treated plants were short lived with CERs suppressed 17 to 29% of control (POC) at 4 and 12 days after treatment (DAT), respectively. Plants treated at 23/18 [degrees]C with PGRs typically had short-lived increases in CERs following CER suppression. A similar pattern of CER response to PGR treatment was observed at the 30/25[degrees]C temperature regime. Quantum efficiency was unaffected, but plants treated with PGRs had reduced root growth. PAC caused the greatest reduction in TRL and SA while increasing root diameter. A decline in TRL and SA in conjunction with increased tillering indicates that PGR reduced TRL and SA on a tiller basis. Changes in single-leaf CERs do not fully explain PGR-induced changes in plant growth.

Any future precision turfgrass management system will benefit from the evaluation of turfgrass stress through indirect measurements of plant components. One such component might be the accumulation dynamics of total nonstructural carbohydrates (TNC). The effects of mowing height (MH) on TNC concentrations were measured in a field experiment. Clippings were collected from eight creeping bentgrass cuifivars {Agrostis palustris Huds.[= A. stolonifera var. palustris (Huds.) Farw.l]} mowed at three different heights (0.64, 1.27, 1.90 cm) from 1998 through 2001. Clippings were evaluated 29 times by sampling early in the photoperiod before 1200 h. Collected clippings were instantly frozen in liquid nitrogen and freeze-dried before TNC analyses. The TNC levels were predicted with near infrared reflectance spectroscopy (NIRS) after building a predictive equation for each carbohydrate fraction with conventional laboratory values. Seasonal trends in TNC concentrations and differences in TNC accumulation among creeping bentgrass cultivars were also evaluated. Mowing heights showed significant differences in TNC content, with 0.64-cm mowed plots having higher TNC levels than 1.27- and 1.90-cm mowed plots on 13 of the 29 dates of evaluation. No consistent differences were observed in TNC concentrations among different cultivars across different growing seasons. However, there were significant seasonal fluctuations in average TNC content at all MHs. The average TNC content of the clippings during 1999 and 2000 started decreasing in mid-July, showing the lowest TNC content in August. The average TNC content showed an increasing trend in September, exhibiting the highest amount of TNC accumulation in October and November., ONE OF THE most important goals in managing golf course fairway turf is maintaining plant health. Any cultural practice directed toward fairway turf will be most efficient when the turf [...]

Abstract: Annual row crops dominate agriculture around the world and have considerable negative environmental impacts, including significant greenhouse gas emissions. Transformative land‐use solutions are necessary to mitigate climate change and restore critical ecosystem services. Alley cropping (AC)—the integration of trees with crops—is an agroforestry practice that has been studied as a transformative, multifunctional land‐use solution. In the temperate zone, AC has strong potential for climate change mitigation through direct emissions reductions and increases in land‐use efficiency via overyielding compared to trees and crops grown separately. In addition, AC provides climate change adaptation potential and ecological benefits by buffering alley crops to weather extremes, diversifying income to hedge financial risk, increasing biodiversity, reducing soil erosion, and improving nutrient‐ and water‐use efficiency. The scope of temperate AC research and application has been largely limited to simple systems that combine one timber tree species with an annual grain. We propose two frontiers in temperate AC that expand this scope and could transform its climate‐related benefits: (i) diversification via woody polyculture and (ii) expanded use of tree crops for food and fodder. While AC is ready now for implementation on marginal lands, we discuss key considerations that could enhance the scalability of the two proposed frontiers and catalyze widespread adoption. [ABSTRACT FROM AUTHOR]