Response of nitrogen and phosphorus leaching and soil properties to applications of biosolids during turfgrass establishment

Regulations for total maximum daily loads require management of phosphorus loading from farms and municipalities. This study evaluated environmental impacts of a system for using and exporting the phosphorus in composted dairy manure (CDM) and composted municipal biosolids (CMB) through turfgrass sod. Responses of soil physical, chemical, and biological properties within and below the sod layer were monitored during turfgrass establishment in two experiments under greenhouse conditions. During turf establishment in column lysimeters, phosphorus and nitrogen leaching from an amended surface layer through soil were evaluated. In addition, growth of turf was related to the observed changes in soil nutrients and properties. In the first experiment, four replications of a factorial design comprised three soil types (USGA greens sand, Windthorst fine sandy loam [fine, mixed, thermic Udic Paleustalf], Houston black clay [fine, smectitic, thermic, Udic Hapustert]), two dairy manure rates ( 200 kg P ha-1, 400kg P ha-1), and two turf species (St. Augustinegrass (Stenotaphrum secundatum [Walt.] Kuntze var. Raleigh) and Tifway 419 Bermudagrass (Cynodon dactylon [L.] Pers. x C. transvaaleensis Burtt-Davy). Columns received three separate leaching events in which a 9-cm depth of distilled water was applied. A similar experimental design was implemented for Experiment 2 in January 2004. Treatments consisted of the same three soils and three volume-based rates of CDM and CMB (0, 150, 250 cm3 L-1) during establishment of St. Augustinegrass turf. Columns received one pore volume of distilled water on three separate occasions. In both experiments, soil physical properties (bulk density, water infiltration rate, and water content) and microbial populations were unaffected by CDM or CMB. Applications of CDM at P-based rates utilized in the first experiment yielded no variation of leaching loss among rates of P or N. Most of the P applied was retained in the top 10 cm of soil. When large volume-based rates were used, leaching losses of P and N varied among CDM or CMB application rates. Leaching losses were only observed in the USGA sand and were highest for the 250 cm3 L-1 rate of CDM or CMB. Regardless of compost source, applications of organic amendments at volume-based rates can increase leaching loss of P and N on sandy soils. However, if P-based rates are used there is little risk for leaching loss of N and P during sod establishment

Biology and management of Pythium root dysfunction in North Carolina

Pythium root dysfunction (PRD) has become an important disease of creeping bentgrass putting greens in the Southeastern U.S., yet very little is known about the etiology, epidemiology, and management of this disease. Seventy-five Pythium isolates were obtained from creeping bentgrass putting greens in NC, SC, GA, and VA. Using morphological and molecular identification techniques, 59 isolates were identified as Pythium volutum and 16 were identified as P. torulosum. A subsample of P. volutum and P. torulosum isolates were tested for pathogenicity in growth chamber experiments. All isolates of P. volutum examined were highly virulent toward creeping bentgrass roots, whereas isolates of P. torulosum were non-pathogenic. Isolates of P. volutum induced drastic reductions in creeping bentgrass root depth and root mass when infected plants were exposed to a four week high temperature regime. Growth chamber experiments were conducted to determine the impact of temperature on infection of creeping bentgrass roots by P. volutum. This was conducted by varying the temperature during a four week infection period, after which the plants were exposed to a four week heat treatment. Symptoms characteristic of PRD developed in the 12°C, 16°C, 20°C, and 24°C infection temperature treatments, but not in the 28°C and 32°C treatments. Root depth and root mass was reduced prior to heat exposure in only the 12°C, 16°C, and 20°C treatments. After a four week exposure to 32°C/26°C (day/night), considerable reductions in root depth and root mass were observed in all infection temperature treatments except for the 28°C and 32°C treatments. Field experiments were conducted to evaluate fungicides for preventative control of PRD. Applications of pyraclostrobin provided the best and longest lasting preventative suppression of PRD symptoms. Azoxystrobin and cyazofamid provided moderate levels of preventative suppression and the standard Pythium fungicides were not effective against PRD. In vitro assays were conducted to determine the sensitivity of P. volutum’s to fungicides. Pythium volutum isolates were highly sensitive to pyraclostrobin and cyazofamid, moderately sensitive to azoxystrobin, and the least sensitive to mefenoxam. Growth chamber experiments were performed to evaluate the effects of creeping bentgrass cultivar, organic matter content, and irrigation frequency on development of PRD. ‘Crenshaw’, ‘Syn-96’, and ‘G-6’ were the least susceptible cultivars when compared to ‘Penncross’. The popular cultivars ‘A-1’ and ‘A-4’ were moderately susceptible and ‘LS-44’, ‘G-2’ and ‘Penncross’ were the most susceptible cultivars. Organic matter added at the time of establishment did not have an effect on PRD development. Symptoms of PRD were most severe when creeping bentgrass was irrigated 6 times a week when environmental conditions were conducive for infection by P. volutum. When creeping bentgrass was irrigated 3 or 4 times a week, PRD symptoms were less severe and turf quality did not decline. Another series of growth chamber experiments were established to determine the effects of P. volutum infections on creeping bentgrass nitrate uptake, evapotranspiration, and photosynthesis. Nitrate uptake was elevated in creeping bentgrass plants that were infected with P. volutum when compared to the non-inoculated controls. Evapotranspiration was similar among inoculated and non-inoculated plants

Characterizing prostate cancer risk through multi-ancestry genome-wide discovery of 187 novel risk variants.

The transferability and clinical value of genetic risk scores (GRSs) across populations remain limited due to an imbalance in genetic studies across ancestrally diverse populations. Here we conducted a multi-ancestry genome-wide association study of 156,319 prostate cancer cases and 788,443 controls of European, African, Asian and Hispanic men, reflecting a 57% increase in the number of non-European cases over previous prostate cancer genome-wide association studies. We identified 187 novel risk variants for prostate cancer, increasing the total number of risk variants to 451. An externally replicated multi-ancestry GRS was associated with risk that ranged from 1.8 (per standard deviation) in African ancestry men to 2.2 in European ancestry men. The GRS was associated with a greater risk of aggressive versus non-aggressive disease in men of African ancestry (P = 0.03). Our study presents novel prostate cancer susceptibility loci and a GRS with effective risk stratification across ancestry groups