Kentucky bluegrass is known to take 14 to 21 days for their germination which is longer than most other cool-season grasses. Successful germination and establishment are dependent on planting depth, soil moisture content, temperature, light, and nutrient. Mulches can help turf establishment quickly and successfully by controlling temperature and maintaining moisture. Phosphorus is well-known for energy storage and transfer which may affect germination and establishment. The objective of the study was to evaluate various phosphorus rates and turf mulches for establishment from Kentucky bluegrass seed. Two laboratory studies and one field study were conducted in the condition of proper and excessive temperature range for Kentucky bluegrass germination. Five different mulch materials and control of no mulch was treated to cover Kentucky bluegrass after seeding to retain soil moisture and temperature of soil surface. Black and white poly-vinyl chloride (PVC) film were used as material for mulch. The 15% pore space were made with holes of 0.4 cm diameter on black and white PVC to increase light transmittance, respectively. Before seeding, phosphate was applied at the rate of 0, 5, 10, and 20 g m-2 using Fused Magnesium Phosphate (0-17-0). Phosphorus application had negative effects on germination of Kentucky bluegrass seed when the air temperature is higher than optimal range for cool-season grasses and mulch material can lead to temperature increase which may inhibit Kentucky bluegrass germination.
Figures & Tables
Fig. 1. Mean germination rate of ‘Midnight’ Kentucky bluegrass for phosphorus (P) rate at the final rating date. Each mean was calculated from 15 observations (three replications×no mulch and four mulch materials). (A) Germination rate was measured from the laboratory study on season A that was performed under the condition of air temperature ranged from 16 to 22℃ as proper temperature range for cool-season grass growth. (B) Germination rate was measured from the laboratory study on the season B that was performed under the condition of air temperature ranged from 19 to 45℃ as excessive temperature range for cool-season grass growth. a, b: Means with the same letter within P rates are not significantly different according to Fisher’s LSD (P =0.05).