Golf Course Management

NOV 2012

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research accumulated in the root zone during the first two years of the study. This ensured that there was no difference in soil salinity between plots irrigated with saline water and those irrigated with pota- ble water at the onset of the second establishment experiment, as our data analysis confirmed. The plots were fertilized with 15-15-15 fertil- 2005 and 2007. Fertilizer applications were made approximately every 15 days during the first two months of establishment and every 30 days there- after. Nitrogen was applied from 15-15-15 fertil- izer at rates totaling 5.1 pounds nitrogen/1,000 square feet (25 grams/square meter) in 2006 and 4.1 pounds/1,000 square feet (20 grams/square meter) in 2008. izer at a rate of 1 pound nitrogen/1,000 square feet (5 grams/square meter) before each seed- ing. A total of 10.2 pounds/1,000 square feet (50 grams/square meter) each of nitrogen, phospho- rus (P2 O5 ) and potassium (K2 O) were applied in Irrigation In 2005 plots irrigated with both saline and potable water received 80% ETo. From March through August 2007, plots irrigated with pota- ble water received 95% of ETo, and plots irri- gated with saline water received 110% ETo. From March to October in both 2006 and 2008, plots irrigated with potable and saline water received 75% and 110% ETo, respectively. The additional volume of water added to the saline-irrigated plots compared to those irrigated with potable water corresponded to the leaching fraction necessary to prevent excessive buildup of salt in the root zone. The area was mowed with a rotary mower at a height of 2 inches (5 centimeters), with clippings returned. Weeds were removed manually during the entire four-year research period. Data collection and analysis Digital image analysis was used to assess stand establishment (3,6). Three pictures per plot were analyzed for green coverage and averaged for statis- tical analysis. Each image covered an area of 3 feet × 3.6 feet (0.9 meter × 1.1 meters). During the 2005 establishment period, photos were taken every two weeks in February and March and monthly from April to June. Establishment in 2007 was evaluated based on images taken on April 2 (18 days after seeding, May 2 (48 days after seeding), and June 19 (96 days after seeding). Turfgrass quality was assessed by means of a visual rating scale of 1 to 9, recommended by the National Turfgrass Evaluation Program, where 1 = dead turf and 9 = dark green, uniform turf (4). Turfgrass quality of each plot was determined monthly from May to October in 2006, from May to July in 2007, and twice a month from March to November in 2008. Normalized Difference Vegetation Index (NDVI) readings were collected monthly from June to October in 2006 and twice monthly from March to November in 2008 to substanti- ate visual quality ratings. A Greenseeker (Trimble Navigation Ltd., Ukiah, Calif.) was used to take measurements at approximately 3 feet (90 cen- timeters) above the surface at a normal walking speed. NDVI values were recorded and stored in a data logger (8). The mean vegetation indices from each plot were calculated and used for further sta- tistical analyses. Salinity buildup in the root zone was deter- mined on soil samples collected at depths of 0 to 4 inches (0 to 10 centimeters) and 4 to 12 inches (10 to 30 centimeters) in October 2005 and May and September in 2006. Soil samples at depths of 0 to 4 inches and 4 to 8 inches (10 to 20 centimeters) were collected in July 2007 and February, June, September and November 2008. Samples were subsequently analyzed for electrical conductivity, sodium and Sodium Adsorption Ratio (SAR). Results Turfgrass establishment Data analyses revealed that neither water treat- A photo of the study site in November 2008 at the end of the four-year study testing the effects of non-chemical water conditioners on turfgrass quality and root-zone salinity. 92 GCM November 2012 ment alone nor any of the combinations of water treatment, water quality and days after seed- ing had a significant effect on perennial ryegrass establishment in either 2005 or 2007. However, irrigation with saline water significantly delayed establishment. At the end of both establish- ment periods, coverage by perennial ryegrass was

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