phosphorus

After I wrote this post about the differences in P fertilizer recommendations when using different methods for soil test interpretation, I heard from some readers that it seemed I was taking something simple—MLSN—and making it seem complicated.

Daniel Hahn and Romain Giraud wrote an article on LinkedIn about fertilisation decisions based on MLSN and STERF’s precision fertilisation (SPF). If you are at all interested in this topic, I hope you’ll read their article.

Doug Soldat joined me for an ATC Office Hours discussion about leaf nutrient analyses (tissue testing) for turfgrass. I’ve embedded the video at the end of this post, link to it here, or listen to the podcast version here.

These pots of variegated tropical carpetgrass (Axonopus compressus) received an application of granular 16-16-16 fertilizer twelve days before this photo was taken. The grass on the right responded with a lot more growth than did the grass at left.

On February 28, 2020, I cut some Wana manilagrass rhizomes to a two node length and planted those two node rhizomes in four sand-filled pots. After eight days, I applied the first fertilizer treatment.

On February 28, I planted ‘Wana’ manilagrass as two node rhizomes in sand-filled pots. All pots have had irrigation and rainfall. One pot has not been fertilized. One has received only N from urea.

I was reading the “Cultural Aspects of Disease Management” chapter in Management of Turfgrass Diseases by Dr. Vargas and came across this gem about soil pH: “Most of the literature tells you that the soil pH should be maintained at the optimum level for turfgrass growth (between 6 and 7).

The MLSN guideline for phosphorus (P) is 21 ppm. I usually recommend enough P fertilizer to keep soil P, as measured by the Mehlich 3 extractant, from dropping below 21 ppm.

After last week’s post about the soil test levels where P deficiency symptoms were seen, Paul Johnson wrote to remind me about another experiment: “This is always a topic of interest to me, beginning with the study I did in the early 2000s.

When I see a photo like the P deficiency one shared by Ben Pease (see photo below), I am really curious to know the soil test levels of the element.