Another tool used by some superintendents is tissue testing. I personally work with a lab in Pittsburgh, PA on all our water, soil and tissue testing. Dr. David York (a Penn State and Cornell graduate) does all our testing and recommendations. In order to obtain such a report, every 2-3 weeks I overnight ship two cups of fresh grass clippings from a particular green. Dr. York has a device that analyzes the clippings and breaks down the percentage of each nutrient found in the grass. This tells me exactly what is getting into the plant. Soil testing is also beneficial on a much more occasional basis; about 3-4x per year for greens. Many nutrients have relationships that impact one another. For example, low Calcium will prohibit Potassium from getting into the plant. To combat this, I have been applying a lot of Calcitic lime. With the amount of rainfall we receive, the calcium is regularly stripped from the soil and leached out. The more rain, the more inputs are required. While tissue testing isn't an inexpensive process, it does help us make decisions on what we need to apply rather than guessing. Overall, it saves money. Greenkeeping is no doubt an art and science with this being the science of it.