Leaf cuticle characteristics and foliar nutrient uptake by a cool-season and warm-season turfgrass

A series of field, greenhouse, growth chamber, and laboratory studies were conducted to increase our understanding of foliar absorption in high-maintenance turfgrasses and evaluate how various seasonal, anatomical and physiological dynamics may affect the permeation process. The following objectives were proposed on creeping bentgrass and hybrid bermudagrass putting green turf: (1) to comprehensively analyze the morphology and chemical make-up of the leaf cuticle; (2) to directly measure the seasonal uptake of foliar-applied nitrogen, applied as 15N urea, under field conditions; (3) to document the extent of N loss via ammonia volatilization following foliar-applied urea; (4) and to investigate the use of various inorganic and organic sources of N and their effect on foliar N absorption efficiency. Older leaves possessed significantly greater cuticle proper thickness compared to younger leaves. Presence of epicuticular wax crystalline structures highlighted potential impact on absorption efficiency of foliar-applied chemicals and fertilizers. The long-chain primary alcohol (1-hexacosanol) comprised 90% of creeping bentgrass leaf cuticle wax and variably influenced foliar N absorption efficiency. Foliar uptake of urea-N and absorption into plant tissues occurred rapidly, generally peaking at 4 h after treatment. Foliar absorption of N supplied as urea was affected by month of application and year, ranging variably from 36--69% for creeping bentgrass and 38--62% for hybrid bermudagrass and volatile loss of NH3-N was negligible (< 3%). Foliar uptake of the various N compounds by creeping bentgrass ranged from 31--56% of the N applied at 8 h after application. Foliar absorption of KNO3 into aerial plant parts was lower than most of the organic and inorganic sources tested, while many of the compounds supplied N to the plant in similar proportions.