Kentucky bluegrass cultivar root and top growth responses when grown in hydroponics

The fine texture and fibrous nature of turfgrass root systems make it difficult, tedious, and time consuming to measure root production, distribution, and plasticity. Timely, labor-efficient methods for turfgrass root assessment would be helpful. The objectives of this study were to: (i) evaluate Kentucky bluegrass (Poa pratensis L.) cultivars and experimental lines for root production, depth, and distribution in hydroponics; (ii) determine ability to redistribute roots as solution levels decline; and (iii) assess production of clipping yield, verdure, and top growth. Fifteen Kentucky bluegrass cultivars and one experimental line were studied in hydroponics experiments. 'Georgetown' produced the most root mass at 1460 mg, while 'Kenblue' and NE 80-88 had the least production at 1122 and 1099 mg, respectively. Total root production varied by 25% among entries. Root production was greatest for all cultivars in the range of 0 to 300 mm, declining with depth, but all entries produced roots at depths >600 mm. NE 80-88 had 90% of its root growth in this range, while 'Touchdown' had 71%. Root production declined considerably at depths >450 mm. 'Birka', 'Dormie', 'Eclipse', and Touchdown had the greatest roots, while 'Aspen', Georgetown, NE 80-88, and 'Park' had the least. Touchdown had the most roots (i.e., 27% of root mass) remaining in the hydroponic solution at the end of each experiment, while NE 80-88 had the least at 8.7%. Total top growth varied among the Kentucky bluegrass cultivars by 42%. 'America' produced the most total top growth at 9.2 g, while Kenblue had the least at 5.4 g. Aspen produced the most clippings with a yield of 3.7 g, while 'Challenger' and Eclipse had the lowest production at 2.1 g. Results from these experiments indicate hydroponic systems can be used to effectively separate Kentucky bluegrass genotypes for rooting and top growth responses. Furthermore, these results support the potential to select Kentucky bluegrass genotypes with improved rooting characteristics, such as root distribution and plasticity. Additional research is needed to relate results developed from hydroponics studies with field conditions.