Minimalist turfgrass nutrition
That’s the title of my seminar today at the Alberta Property Manager’s Conference. Minimalist is not a word I would often use, but when I looked at the conference program, that was the title I saw. Rather than requesting a change, I decided to talk about it, and explain why minimalist isn’t the way I would describe this. These are the slides – also embedded below – and this is what I’m going to discuss.
We can start by thinking about what we are trying to accomplish with turfgrass nutrition. We want to produce a surface, and that is done by adjusting the growth rate of the grass while preventing nutrient deficiencies. To prevent nutrient deficiencies, one needs to ensure the grass is supplied with all of each nutrient that it can use. Excepting nitrogen of course, which is what we will use to adjust the growth rate.
It follows that the minimum amount to supply is all that the grass can use.
Adding more than the grass can use, or more than the soil can hold (and adding fertilizer does not simultaneously increase the soil’s ability to hold it) has no effect on the grass. It’s a waste. It follows that the maximum amount to supply is also all that the grass can use.
Because the minimum amount to supply and the maximum amount to supply are the same, I refer to this as the right amount, or just what the grass requires. Why is this sometimes referred to as minimalism? It is because use of conventional guidelines results in fertilizer recommendations that can be more than the grass can use or more than the soil can hold. Compared to the conventional guidelines, the approach I describe might be considered minimalistic.
How can we accomplish the supply of nutrients in just the right amount? If there is no soil testing, then one can assume the soil will supply nothing, and it makes sense to supply 100% of what the grass can use. The grass uses nutrients in the amount that it grows. One can put an upper estimate on growth and nutrient use by looking at N supply to the grass. One can also measure how much the grass is growing.
If there is soil testing, then one knows the quantity of nutrients in the soil. Now the amount that it makes sense to supply as fertilizer is the amount the grass uses, minus the amount in the soil. If the use is large and the soil amount is small, the fertilizer recommendation will be high. If the use is small and the soil amount is large, then none of that element will be required as fertilizer. This simple calculation needs an adjustment though, because we never want to use up all of an element in the soil. We don’t want the quantity to go to zero. This is where MLSN comes in, as a reserve amount in the soil.
I use the MLSN guidelines to make these calculations, because the MLSN guideline level gets added to the grass use amount. In this way it acts as an extra amount of nutrients that will remain in the soil, never touched by the grass.
This is a simple calculation that can be demonstrated by an analogy about apples, or about beer. You can read about the apple or beer analogy in the 4th MLSN newsletter. Also, sign up for the MLSN or other ATC newsletters here.