This pretty much covers everything

In January 2016 at the Northern Green Expo in Minnesota, I got to talk about light, water, temperature, and nitrogen. Those are the factors that influence growth, and getting the growth rate right is what greenkeeping is all about.

There were five different seminars, all linked by that common theme. I prepared this extensive handout.

The (New) Fundamentals of Turfgrass Nutrition

Most seminars, presentations, articles, and even semester-long courses about turfgrass nutrition discuss the functions of different elements. Potassium is involved in stomatal regulation, phosphorus is essential for root development, calcium for cell wall strength, and so on. All true, but largely irrelevant for the turfgrass manager. What the turfgrass manager must know is not the function of each element, but the quantities — is enough of this element present to meet the grass requirements, or is it not? If it isn’t present in adequate quantities, how much must be added to ensure the grass has enough? In this seminar, the fundamentals of turfgrass nutrition will be explained, with a focus on an understanding of the amount of each nutrient that is required.

Nutrient Use by the Grass and Nutrient Supply by the Soil

Grass grows in soil, and nutrients used by the grass come either from the soil or from fertilizer. When the soil contains enough of an element to meet all of the grass requirements, none of that element is required as fertilizer. When the grass can use more of an element than can be supplied by the soil, that element must be applied as fertilizer. This seminar will explain how to estimate the maximum amount of an element the grass can use, how to identify the quantity that can be supplied by the soil, and how to use those two amounts to get an estimate of the amount that may be required as fertilizer.

Calculating the Fertilizer Requirement for Any Turfgrass, Anywhere

This presentation builds on the fundamentals of the turfgrass nutrition talk, and the nutrient use and nutrient supply talk, by explaining a system by which a turfgrass manager can calculate the amount of any element required by any turfgrass, under any growing condition, anywhere in the world. Some common misapprehensions about turfgrass nutrition and soil testing will also be discussed. The minimum levels for sustainable nutrition (MLSN) guidelines for interpreting soil test results, and the temperature-based turfgrass growth potential (GP), which were introduced in the two previous seminars, will be discussed in even more detail.

Soil Water Management: Timing, Amount and Syringing

Fifteen years ago, it was rare to use a soil moisture meter. Today, it seems that almost every turfgrass manager has some idea of the soil moisture content. In this presentation, Micah Woods will show that daily irrigation can use less water than infrequent irrigation, while maintaining a lower soil moisture content than deep and infrequent irrigation. Woods will explain how soil moisture meters can be used to prove that, how they can be used to measure the real evapotranspiration rate, and why syringing turf for the purpose of cooling the surface is a waste of time, water, and energy.

Instead of Shade, Let’s Talk About Light

Shade from trees, buildings, clouds or mountains affects a lot of turfgrass areas, and shade can make it impossible to produce the desired turfgrass conditions. Rather than talk about the impossible, in this presentation Woods will talk about light. Specifically, he’ll discuss photosynthetically active radiation (PAR), the photosynthetic photon flux density (PPFD), and the daily light integral (DLI). These sound complicated but are quite simple and can be easily measured or estimated. With an understanding and ability to measure and communicate about PAR, PPFD, and DLI, it makes it a lot easier to manage those previously impossible shade problems.