Increased CO2 release from soils resulting from agricultural practices such as tillage has generated concerns about contributions to global warming. Maintaining current levels of soil C and/or sequestering additional C in soils are important mechanisms to reduce CO2 in the atmosphere through production agriculture. We conducted a study in northern Alabama from 2003 to 2006 to measure CO2 efflux and C storage in long-term tilled and non-tilled cotton (Gossypium hirsutum L.) plots receiving poultry litter or ammonium nitrate (AN). Treatments were established in 1996 on a Decatur silt loam (clayey, kaolinitic thermic, Typic Paleudults) and consisted of conventional-tillage (CT), mulch-tillage (MT), and no-tillage (NT) systems with winter rye [Secale cereale (L.)] cover cropping and AN and poultry litter (PL) as nitrogen sources. Cotton was planted in 2003, 2004, and 2006. Corn was planted in 2005 as a rotation crop using a no-till planter in all plots, and no fertilizer was applied. Poultry litter application resulted in higher CO2 emission from soil compared with AN application regardless of tillage system. In 2003 and 2006, CT (4.39 and 3.40 micromol m(-2) s(-1), respectively) and MT (4.17 and 3.39 micromol m(-2) s(-1), respectively) with PL at 100 kg N ha(-1) (100 PLN) recorded significantly higher CO2 efflux compared with NT with 100 PLN (2.84 and 2.47 micromol m(-2) s(-1), respectively). Total soil C at 0- to 15-cm depth was not affected by tillage but significantly increased with PL application and winter rye cover cropping. In general, cotton produced with NT conservation tillage in conjunction with PL and winter rye cover cropping reduced CO2 emissions and sequestered more soil C compared with control treatments.
The need for water conservation continues to increase as global freshwater resources dwindle. Turfgrass mangers are adapting to these concerns by implementing new tools to reduce water consumption. Time-domain reflectometer (TDR) soil moisture sensors can decrease water usage when scheduling irrigation, but nonuniformity across unsampled locations creates irrigation inefficiencies. Remote sensing data have been used to estimate soil moisture stress in turfgrass systems through the normalized difference vegetation index (NDVI). However, numerous stressors other than moisture constraints impact NDVI values. The water band index (WBI) is an alternative index that uses narrowband, near-infrared light reflectance to estimate moisture limitations within the plant canopy. The green-to-red ratio index (GRI) is a vegetation index that has been proposed as a cheaper alternative to WBI as it can be measured using digital values of visible light instead of relying on more costly hyperspectral reflectance measurements. A replicated 2 × 3 factorial experimental design was used to repeatedly measure turf canopy reflectance and soil moisture over time as soils dried. Pots of ‘007’ creeping bentgrass (CBG) and ‘Latitude 36’ hybrid bermudagrass (HBG) were grown on three soil textures: United States Golf Association (USGA) 90:10 sand, loam, and clay. Reflectance data were collected hourly between 07:00 and 19:00 using a hyperspectral radiometer and volumetric water content (VWC) data were collected continuously using an embedded soil moisture sensor from soil saturation until complete turf necrosis by drought stress. The WBI had the strongest relationship to VWC (r = 0.62) compared to GRI (r = 0.56) and NDVI (r = 0.47). The WBI and GRI identified significant moisture stress approximately 28 h earlier than NDVI (p = 0.0010). Those metrics also predicted moisture stress prior to fifty percent visual estimation of wilt (p = 0.0317), with lead times of 12 h (WBI) and 9 h (GRI). By contrast, NDVI provided 2 h of prediction time. Nonlinear regression analysis showed that WBI and GRI can be useful for predicting moisture stress of CBG and HBG grown on three different soil textures in a controlled environment.
Dollar spot (Clarireedia spp.) is a damaging turfgrass disease. Ferrous sulfate (FeSO 4 ) suppresses dollar spot with little risk of resistance. Optimizing FeSO 4 applications is crucial for adequate dollar spot suppression. Supplementing FeSO 4 applications with chlorothalonil fungicide could also increase efficacy against dollar spot and longevity of disease suppression. Four experiments were conducted to determine the 1) optimal water carrier volume for FeSO 4 , 2) proper nozzle selection for FeSO 4 applications, 3) most efficacious rate combination of FeSO 4 and chlorothalonil, and 4) longevity of chlorothalonil efficacy when applied in conjunction with FeSO 4 for dollar spot suppression on creeping bentgrass (Agrostis stolonifera L.). These studies were conducted on either putting greens mown at 3.2 to 6.4 mm or fairways mown at 16.5 mm. The following carrier volumes were tested in Experiment 1: 281, 421, 842 and 1684 L ha -1 . For Experiment 2, Turbo FloodJet (TF), Turbo TeeJet Induction (TTI), Air Induction Turbo TwinJet (AITTJ), and Extended Range Flat Fan (XRFF) nozzles were used to determine optimal nozzle type. In Experiment 3, chlorothalonil was applied at 0, 2.28, 4.57, 6.86 and 9.16 kg a.i. ha -1 with or without 48.8 kg ha -1 of FeSO 4 . In Experiment 4, 48.8 kg ha -1 of FeSO 4 was applied biweekly and chlorothalonil was curatively applied at 8.2 kg a.i. ha -1 when infection centers per plot reached 30. Water carrier volume had no effect on dollar spot suppression, the AITTJ and XRFF nozzles provided the greatest disease suppression and turf quality, FeSO 4 reduced effective chlorothalonil rates by up to 68.5% and FeSO 4 increased longevity of chlorothalonil efficacy.
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