Evaluation of microlysimeters used in turfgrass evapotranspiration studies with the dual-probe heat-pulse technique

Microlysimeters (ML) are commonly used in turfgrass evapotranspiration (ET) studies. No standard exists for ML which has resulted in multiple designs that may affect soil moisture. The effects of ML design on volumetric soil water content ([Greek letter theta subscript v]) were investigated using the dual-probe heat-pulse (DPHP) technique. DPHP sensors were installed at 5, 15, and 25 cm in the ambient soil profile and in 3 designs of ML: 1) 15 cm diam. x 30 cm, mesh base, soil fill (MSL); 2) 15 cm diam. x 30 cm, plexiglass base (one drainage hole), soil fill (PSL); 3) 10 cm diam. x 20 cm, mesh base, soil (intact cores) (MSNL). Sleeves and a 5 cm layer of gravel were placed in MSL and PSL. DPHP estimates of [Greek letter theta subscript v] revealed that soils consistently dried faster in MSL and PSL than in the ambient profile, probably because of higher LAI and biomass in MSL and PSL than in surrounding turf, limitations of roots to extract soil water only from ML, and evaporation through open bases. In MSNL, [Greek letter theta subscript v] was similar to but may have been in hydraulic contact with ambient soils. Correlation was good between [Greek letter theta subscript v] determined by DPHP and by gravimetric methods; DPHP sensors on average (all ML) measured [Greek letter theta subscript v] to within 0.025 m[superscript 3] m[superscript minus 3] of gravimetric estimates. ET estimates varied significantly among ML and were strongly correlated to LAI and aboveground biomass (r=0.85). Results suggest that establishment/maintenance of similar LAI and biomass between ML and surrounding turf may be more important than ML design in providing accurate ET estimates, and bases should be sealed during ET measurements to prevent hydraulic contact with soil, drainage, or evaporation through bases

Growth Responses of Zoysia spp. under Tree Shade in the Midwestern United States

‘Meyer’ zoysiagrass (Zoysia japonica Steudel) is commonly planted on home lawns and golf courses in the transition zone; however, poor shade tolerance limits its widespread use. This study was conducted to determine changes and differences in growth among selected Zoysia cultivars and progeny under a natural shade environment over a 3-year period in the transition zone. The study was initiated in June 2010 at the Rocky Ford Turfgrass Research Center in Manhattan, KS. Soil type was a Chase silt loam (fine, montmorillonitic, mesic, Aquic, Argiudoll). Zoysia genotypes were sodded in 0.37-m2 plots and arranged in a randomized complete block with five replications under silver maple (Acer saccharinum L.) shade that resulted in a 91% reduction in photosynthetically active radiation (PAR). Genotypes included ‘Zorro’ [Z. matrella (L.) Merrill], ‘Emerald’ [Z. japonica × Z. pacifica (Goudswaard) Hotta & Kuroki], ‘Meyer’, Chinese Common (Z. japonica), and experimental progeny Exp1 (Z. matrella × Z. japonica), and Exp2 and Exp3 [(Z. japonica × Z. pacifica) × Z. japonica]. ‘Zorro’ and ‘Emerald’ experienced winter injury, which negatively affected their performance. Tiller numbers decreased 47% in ‘Meyer’ from June 2010 to June 2012, but declines in [(Z. japonica × Z. pacifica) × Z. japonica] progeny were only 1% for Exp2 and 27% for Exp3, and both Exp2 and Exp3 maintained high percent green cover throughout the study. In general, by the third year of evaluation, progeny of [(Z. japonica × Z. pacifica) × Z. japonica] had higher quality ratings and higher tiller numbers than ‘Meyer’ and may provide more shade-tolerant cultivar choices for transition zone turf managers

Lawn-watering perceptions and behaviors of residential homeowners in three Kansas (USA) cities: implications for water quantity and quality

Urbanization is increasing the land area covered with turfgrasses, which may have implications for water quantity and quality. The largest sector of turfgrass is residential lawns. Our objectives were to survey residential homeowners in three Kansas cities about their perceptions, knowledge, and behaviors when irrigating their lawns; each city has distinctive water quantity and quality issues. Surveys were mailed to 15,500 homeowners in Wichita, 10,000 in Olathe, and 5,000 in Salina; the return rate was 11-13%. Wichita residents watered more frequently than Olathe and Salina, possibly because of greater evaporative demand than Olathe, and cheaper water and less concern about water shortages than Salina; Salina and Wichita have similar evaporative demands but Salina had a recent water crisis. Salina homeowners were most concerned about keeping their water bill from getting too high, probably because of higher water costs than the other cities. Overall, 45-60% indicated it was moderately to very important their lawns looked green all the time, while 65-77% ranked water conservation at the same level of importance. Significantly, 61-63% did not know how much water their lawns required and 71-77% did not know how much water they applied to their lawns when they irrigated. About 7-9% swept or blew clippings or lawn-care products directly into streets or storm drains, which run directly into local streams or reservoirs; 9% in Wichita is ~9,000 homeowners. The homeowner’s lawn irrigation knowledge and habits must be improved to help conserve water and protect water quality

High and Low Management Input Regimes Result in Similar Net Carbon Sequestration Rates in Zoysiagrass Golf Course Fairway Turf

This study was conducted from 2013–2016 to determine how irrigation and N fertilization may be managed to enhance carbon (C) sequestration in turf. In this study, the annual rate of change in soil organic carbon (ΔSOC) was measured under two management regimes, a high management input regime (HMI) and low man­agement input regime (LMI), in a ‘Meyer’ zoysiagrass (Zoysia japonica Steud.) golf course fairway. Both management regimes maintained acceptable turf quality and at least 75% green cover during both summers. In both management regimes, soil organic carbon (SOC) increased after the 3.16-yr (1154-d) period indicating that C was sequestered in the soil. The C emissions from turfgrass maintenance prac­tices (mowing, irrigation, and fertilization and pesticide applications) are known as “hidden carbon costs” (HCC). The average gross C sequestration rates for the two treatments were not statistically different at 1046 kg C/ha/yr and 976 kg C/ha/yr in HMI and LMI, respectively, prior to subtracting HCC. Once the total estimated HCC was included, the average net sequestration rate was 412 kg C/ha/yr and 616 kg C/ha/yr in HMI and LMI, respectively, with no statistical differences. Our study indicates high and low management input regimes result in similar net C sequestra­tion rates in zoysiagrass golf course fairway turf

Minimal Water Requirements of Cool-Season Turfgrasses for Survival and Recovery After Prolonged Drought

Sodded tall fescue (TF) and Kentucky bluegrass (KBG) turfgrasses were exposed to prolonged drought at several levels of deficit irrigation from 0% to 50% of reference evapotranspiration (ET) within the first year of establishment. Tall fescue watered at 40% and 50% ET maintained minimally acceptable performance longer during the dry-down phases and recovered faster after rewatering than lower ET treatments. Tall fescue with no water input (0% ET) maintained minimally acceptable performance for about 5 weeks, which was longer than KBG watered at 50% ET, which remained acceptable for less than 3 weeks during the dry down. Although KBG watered at 50% ET performed best among irrigation treatments for a short period, all treatments went into dormancy similarly in 6–9 weeks and didn’t recover after rewatering in either year. In both years of this study, TF and KBG were sodded the prior fall and thus, had been established for less than 1 year before exposure to severe drought and deficit irrigation. Results indicate that under the conditions of this study (i.e., limited or no irrigation during the first summer after fall sodding in good soil (silty clay loam) of the transition zone of Kansas), TF is a better selection than KBG

Water Requirements of ‘Meyer’ Zoysiagrass for Survival and Recovery After Prolonged Drought

Water restrictions on irrigation are generally not science-based and may cause irreversible damage to turfgrass or inadvertently waste water. The objectives of our study were to evaluate effects of minimum water applications to ‘Meyer’ zoysiagrass (Zoysia japonica Steud.) on 1) turfgrass performance during prolonged dry downs; and 2) survival and recovery thereafter. Zoysiagrass was watered with 0, 5, 10, 15, 20, 25, and 30% reference evapotranspiration (ET) replacement for two months in two consecutive summers under an automated rainout shelter (excluded all rainfall) near Manhattan, KS. Results indicated that irrigation at 20 to 30% ET slowed the decline in zoysiagrass performance compared with no water inputs. Irrigation at 30% ET maintained zoysiagrass at \u3e75 percentage green cover (PGC) in the first year, and even with no water inputs (0% ET) or irrigation at only 5% ET replacement, zoy­siagrass recovered after full irrigation resumed. In the second year, irrigation at 30% ET maintained zoysiagrass at \u3e25 PGC throughout the dry down and it recovered thereafter, but plots with no water inputs (0% ET) or irrigated with 5% ET replace­ment only recovered to 30–42 PGC after 50 days of full irrigation. Water restrictions during severe droughts may conserve more water and reduce turfgrass damage by limiting irrigation of zoysiagrass to 20–30% ET than by using traditional standards such as allowing irrigation for only one day per week

Millimeter Observations of GRB 030329: Continued Evidence for a Two-Component Jet

We present the results of a dedicated campaign on the afterglow of GRB 030329 with the millimeter interferometers of the Owens Valley Radio Observatory (OVRO), the Berkeley-Illinois-Maryland Association (BIMA), and with the MAMBO-2 bolometer array on the IRAM 30-m telescope. These observations allow us to trace the full evolution of the afterglow of GRB 030329 at frequencies of 100 GHz and 250 GHz for the first time. The millimeter light curves exhibit two main features: a bright, constant flux density portion and a steep power-law decline. The absence of bright, short-lived millimeter emission is used to show that the GRB central engine was not actively injecting energy well after the burst. The millimeter data support a model, advocated by Berger et al., of a two-component jet-like outflow in which a narrow angle jet is responsible for the high energy emission and early optical afterglow, and a wide-angle jet carrying most of the energy is powering the radio and late optical afterglow emissionComment: Accepted to ApJ

Considerations with using unmanned aircraft systems in turfgrass

In recent years, small unmanned aircraft systems (sUAS) and advancements in remote sensing technology have provided alternative and more affordable means for monitoring crop health and stress than ground-based (hand-held or vehicle-mounted) or other aerial-based platforms (manned aircraft or satellites). However, few scientific studies have evaluated the application of sUAS in turfgrass systems. The use of sUAS in monitoring turfgrass requires an understanding of basic remote sensing principles; identifying the target of interest and the various sUAS platforms and sensors that provide the necessary resolution and frequencies to measure and monitor that target; calibration of sensors in the field; and data processing considerations. Those topics are discussed, followed by reviews of recent turfgrass field studies conducted to predict and manage drought stress and pest outbreaks, and improve phenotyping capabilities in turfgrass breeding programs. The use of sUAS remote sensing in turfgrass offers unique possibilities and challenges, which are addressed herein

Evaluating Small Unmanned Aerial Systems for Detecting Drought Stress on Turfgrass

This study was conducted to evaluate early detection ability of small unmanned aerial systems (sUAS) technology for drought stress on turfgrass. Certain reflectances collected by sUAS and a handheld device declined more in less irrigated treatments before drought stress was evident in visual quality rating (VQ) and percentage green cover (PGC). The near infrared (NIR) band and GreenBlue vegetation index performed the best consistently for drought stress prediction among the other vegetation indices (VI) or bands from sUAS. Results indicate using ultra-high resolution remote sensing with sUAS can detect drought stress as well as, if not better than, a handheld device before it is visible to the human eye, and may provide valuable evidence for irrigation management in turfgrass

Thermal Imaging Detects Early Drought Stress in Turfgrass Utilizing Small Unmanned Aircraft Systems

Plots of fairway-height creeping bentgrass were watered differently to create a gradient of drought stress from severe deficit irrigation to well-watered, under an automatic rainout shelter in Manhattan, KS. Canopy temperature (Tc) measured by a small unmanned aerial system (sUAS) predicted drought stress approximately 5 days or more before drought symptoms were evident in either turfgrass visual quality (VQ) or percentage green cover (PGC). The ability of Tc to predict drought stress was comparable to the best spectral parameters acquired by sUAS on companion flights [i.e., near infrared (NIR) and GreenBlue VI], and slightly better than with spectral data obtained from handheld sensors. Better drought-prediction ability combined with faster data collection using sUAS indicates significant potential for sUAS-based compared with ground-based drought stress monitoring methods