There’s a lot of lawn fertilizer information and Doc breaks it down in the video below.
“With regard to lowering nutrient inputs thereby reducing the potential risks for negative environmental impacts, as well as certain diseases, the fluid nutrition and foliar feeding programs were far superior; producing comparable results with 25 to 80% less Nitrogen, 5 to 90% less Phosphorus, 55 to 85% less Potassium” http://archive.lib.msu.edu/tic/tgtre/article/2001aug11.pdfhttp://archive.lib.msu.edu/tic/tgtre/article/2001aug11.pdf
“Several studies completed at Michigan State University demonstrated improved turf quality when liquid-based nutrient inputs were combined with granular fertilizers, especially organic sources, than when liquid-based fertilizers were used alone. A 15-year study completed at Ohio State University concluded that an organic fertility program produced greater soil microbial activity than an inorganic fertilizer program, while both programs produced equal levels of organic matter. These results suggest that including granular and liquid inputs in your fertility program could have beneficial effects.” http://www.usga.org/course-care/regional-updates/west-region/2017/what-can-granular-fertilizers-do-for-you.html
“In controlled environment studies, relative humidity was generally above 80 percent with constant temperature. The high humidity would lead to longer spray-droplet drying times and allow for greater fertilizer uptake. The urea-nitrogen uptake efficiencies for field studies in Arkansas ranged from 36 to 69 percent compared to those in Illinois that ranged from 6 to 34 percent. Both studies indicate that most of the nitrogen uptake occurred within four hours after application; however, why do the results differ? In addition to differences in climate, scientists in Arkansas used hollow cone nozzles that produce smaller droplets than the flat-fan nozzles used in Illinois. Smaller droplets would provide more uniform coverage and greater uptake. The height of cut also differed for the two field studies. In Illinois, bentgrass cut at a half-inch was higher than the eighth-inch height of cut in Arkansas” http://www.usga.org/course-care/how-efficient-are-foliar-applied-nitrogen-applications-21474860541.html
“Some slow-release sources, especially ureaformaldehyde (UF) and natural organics, such as Milorganite, give only poor to moderate response in cool weather. The reason for this is that the water-insoluble-nitrogen (WIN) in these sources becomes available to the plant as a function of soil microbial activity” http://pubs.ext.vt.edu/430/430-399/430-399.html
“Foliar Absorption of Nitrogen by Creeping Bentgrass Putting Green Turf Utilizing N Labeled Inorganic and Organic Sources. Chris Steigler, Mike Richardson, Doug Karcher and Aaron Patton, University of Arkansas. This research evaluated the potential for foliar absorption of N/labeled inorganic sources (urea, ammonium sulfate, potassium nitrate) and organic sources (three amino acids). They found only about 40-50 percent of N applied at 0.10 lb. N/M of a liquid application was foliarly absorbed 8-hrs after application. All sources were similar except the potassium nitrate which has low foliar uptake. In summary, if you apply 0.10 lb. N/M, on 0.05 lb. N/M will be absorbed through the leaves. Why pay a premium for products that are “specially formulated” to increase foliar absorption? Also, urea worked as well as the other products, so it appears that only a small portion of your total N budget can be foliarly absorbed.” http://www.usga.org/articles/2010/07/course-care-does-grass-know-the-cost-2147488611.html
“But we recommend a spoon-feeding strategy, which is nice for turfgrass because we’re not shooting for yields but performance and color, which is beneficial,” https://www.golfcourseindustry.com/article/gci1113-foliar-nutrition-fertilizers/
A regular fertilization program that includes foliars sets superintendents up well when a drought comes, Huntoon says. They allow for easier control of nitrogen input, cut down on mowing and improve turf quality, saving money and labor. https://www.golfcourseindustry.com/article/gci1112-foliar-fertilizers-benefits/