Cool-season grass in a tropical climate
Of testing methods, Mehlich 3 as an extractant, and “bespoke testing”

"Think of the soil as a nutrient bank"

Bill Kreuser has written an interesting article about the ideal fertilizer ratio for turfgrass. You will want to read the entire article, which discusses turfgrass nutrient demand, nutrient uptake, soil nutrients, and suggested nutrient ratios for various turf situations. Here are a few highlights:

We first need to recognize that nutrient uptake is controlled by plant nutrient demand and not fertilizer applications.

Fertilizing with P and K is a waste of resources when the soil test reports indicate nutrient levels are already adequate.

Think of the soil as a nutrient bank. When fertilization exceeds plant nutrient demand and other mechanisms of nutrient loss (leaching, denitrification, fixation) then soil test nutrient levels increase. Likewise, soil test nutrient levels will decline when plant uptake and nutrient loss exceed fertilization.

Uptake of all soil nutrients is dependent on turfgrass growth rate ... Since turfgrass is chronically N deficient, N fertilization promotes leaf growth and increases demand for other nutrients.

I encourage you to compare your Mehlich-3 soil test results with the Minimum Levels for Sustainable Nutrition (MLSN) guidelines generated by PACE Turf and the Asian Turfgrass Center. Briefly, if soil test P is much greater than 21 ppm and K is much greater than 37, then there is little reason to apply anything other than straight N.

Try to use the diversity of fertilizer ratios to your advantage.


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