Objective

To evaluate the effects of various application rates and timings/frequencies of an all natural biodegradable product, Brookside H2OExcel, for improved creeping bentgrass turf performance and prevention of localized dry spot when applied to turf grown on a sand-based rootzone.

Experimental Procedures

This field study was conducted at the William H. Daniel Turfgrass Research and Diagnostic Center at Purdue University, West Lafayette IN, from late May-early Aug., 2013. The study area consisted of a sand-based rootzone conforming to USGA rootzone specifications and a mature stand of creeping bentgrass (Agrostis stolonifera L. ‘Pennlinks’) which was maintained according to typical moderate putting green management practices for the region. It was mowed regularly at 0.140 inches with clippings collected, fertilized with approximately 3.0 lbs N/1000 ft2/yr-1. Insecticides and fungicides were applied on a curative basis when needed due to pest outbreaks.

Five experimental treatments (four H2OExcel treatments which varied by application rate or frequency and a widely used commercially available soil surfactant, Cascade Plus, applied at the low label rate) were tested. All treatments were applied with a pressurized CO2 (35 psi) sprayer equipped with a TeeJet Air-induction nozzle calibrated to deliver 2.0 gallons of spray volume per 1000 sq ft. The specific application rates and dates are footnoted in each of the data tables. Immediately following application all treatments were irrigated into the rootzone using a hand-held hose to apply ½ inch of water.

Data collection, experimental design and analysis: Volumetric soil moisture content was measured regularly throughout the study period. Additionally, plots were assessed for overall visual turfgrass quality, wilted/brown turf and turf injury. Canopy greenness by reflectance was measured and values presented are a color index value.

Lastly, the ability of the wetting agents to improve and/or sustain the wettability of the rootzone media with depth (0 to 6 cm) was determined at the beginning and end of the study using the water droplet penetration test. The severity of hydrophobicity was judged based on the following scale of water droplet penetration: 0-5 sec = wettable, 6-60 secs = slightly hydrophobic, 61-600 sec = strongly hydrophobic, and > 600 sec = water repellant.

Each treatment was replicated four times in experimental plots (3 x 6 ft) arranged in a randomized complete block. Prior to initiating the study, turfgrass visual characteristics and soil moisture was measured. Treatments were then assigned to individual plots to ensure homogeneity of values prior to application. All data were subjected to analysis of variance using the SAS system (Statistical Analysis Systems Institute Inc., Cary, N.C.) and mean separation performed using Fisher’s protected least significant difference test at the (P<0.05) level.

Results

Visual quality (Table 1)

• Turfgrass quality (TQ) ratings ranged from 6.3 to 8.3 depending upon the individual rating date. These values varied throughout the study and there were no strong treatment trends or rankings.
• For the study mean, or in other words the average value for the 10 individual rating dates, the values ranged from 6.9 to 7.6. For the H2OExcel treatments, TQ values ranged from 7.2 to 7.4 and no H2OExcel treatment was statistically different from each other and none was different than the untreated control, 6.9.
• Further, all of the H2OExcel treatments were statistically the same as the commercially available soil surfactant, TQ values 7.2 to 7.4 vs. 7.6. Only the commercially available soil surfactant was different than the untreated control, TQ values 7.6 vs. 6.9.
• There were no visible turf injury symptoms associated with any treatment.

Turf wilt (Table 2)

• Across all rating dates, the mean wilted/dry turf values ranged from 0 to 10.5% plot area affected.
• There were not substantial treatment differences observed on most rating dates.
• Among treatments, only the commercially available soil surfactant resulted in consistently less, (values typically 0% wilted/dry turf) wilted/dry turf than the untreated control.
• On 25 July, the date of the most severe wilted turf, two treatments were superior to the untreated control. These were the commercially available soil surfactant had 0% wilted turf and the H2OExcel 1.0 oz/14 day, 2.3 % compared to 10.5% in the untreated control. The aforementioned H2OExcel treatment was not significantly different from any of the other three H2OExcel treatments, ranging from 2.8-4.3 % wilted turf.

Turf color as measured by NDVI (Table 3)

• For quantitative canopy greenness or color there were few conclusive differences among treatments.

Volumetric water content (Table 4)

• Rootzone water content varied throughout the study and means for the entire study ranged from 14-19%.
• For overall study treatment means, the products ranked commercially available soil surfactant (19.0 %) > H2OExcel treatments (15.8-16.3 %) > untreated (14.0 %).

WDPT (Table 5)

• There were no substantial treatment differences on the first two sampling dates for any treatment at any depth. WDPT times increased with increasing sampling date, meaning that hydrophobic rootzone conditions were increasing as the growing season progressed.
• By the third sampling date, the only treatment that was consistently superior to the untreated control for decreasing hydrophobic conditions was the commercially available soil surfactant.