Summary
Field and laboratory studies with creeping bentgrass (Agrostis palustris 'Penncross') growth in a sand/peat (4:1) medium recommended for putting greens showed that turf inoculated with the arbuscular mycorrhizal fungus Glomus intraradices was able to tolerate drought conditions significantly longer than non-mycorrhizal turf.
- Mycorrhizal turf recovered more quickly from wilting than did non-mycorrhizal turf.
- Leaf water potentials remained higher in the mycorrhizal turf and declined at a slower rate than in non-mycorrhizal turf.
- Protection against drought was conferred by G. intraradices when turf was grown under conditions of low phosphorus fertilization (11 mg/l), but the benefits disappeared when the P concentration of the fertilizer was quadrupled to 44 mg/l.
- Of eighteen free amino acids and amides studied, y-amino-n-butyric acid was the best indicator of water stress.
- Mycorrhizal turf maintained significantly higher chlorophyll concentrations (avg 29% more) than did non-mycorrhizal turf during the ten-day-long drought in the field.
Why This Research Matters
This study is particularly relevant for turf managers, golf course superintendents, and anyone growing grass in water-constrained conditions. The 29% higher chlorophyll retention during a ten-day drought is a practical measure of how much longer mycorrhizal grass stays green and healthy without irrigation.
The finding that benefits diminish at high phosphorus fertilization levels is also consistent with broader mycorrhizal science: when plants receive abundant nutrients from external inputs, they reduce their investment in the mycorrhizal relationship. This underscores the value of using mycorrhizal inoculants alongside reduced fertilizer programs -- both for cost savings and for maximizing the symbiotic benefit.