Previous month:
May 2017
Next month:
July 2017

June 2017

How much N is in rain and snow?

I was having a discussion about this last week. "I think it is a tiny amount," I said, "although sometimes I hear really large amounts when people tell me how much N comes in rain. I'll be sure to look it up." I just looked it up, and it is generally a small amount, although there are locations with more.


There are some excellent sources for N deposition data. I looked at:

For an example, I downloaded data for Benton County, Oregon, and Garrett County, Maryland. Compared to the amount of N used by grass, or applied as fertilizer in a year, this isn't very much. I'd guess annual N rates would be about 10 to 15 g/m2 at those locations. Adding 0.1 to 0.3 g N/m2 would be less than 3% of the annual N rate.


This guide has some maps that show the N deposition by location. There are a few hotspots that may get 20 kg/ha; that could be a substantial amount of N, say 10 to 20% of the annual amount used by the grass.

I looked up data for Tower Bridge in London using the APIS site. That was an annual total of 15.7 kg N/ha. That will be a substantial amount of N for turf in that location. I'd say that would be about 20% of the amount a golf course putting green might use in London.

Of turf, roots, and fertilizer

I'd like to make three points.

1- Surfaces can be great, and the roots can be negligible.


If the objective of greenkeeping work is to produce the desired surface, then one only needs enough growth to produce that surface. One also only needs enough roots to produce that surface. Any aboveground growth beyond that required to produce the surface is unnecessary, even problematic. For roots I won't go so far as to say extra ones are problematic, but I might say roots beyond those needed to produce the desired surface conditions are irrelevant.


2- Surfaces can be awful, and roots can be amazing. I've seen some incredible roots on some surfaces that didn't come close to meeting the level desired.



I'd rather have good surfaces than amazing roots.

3- I've been reading about an increase in roots and a simultaneous reduction in organic matter. Jerry Kershasky and I had a recent conversation about this:

Let's say one generates massive roots. Like those on the poor surfaces in section 2, above. Or by increasing the N rate (an easy and underrated method for stimulating root growth) as shown in the precision fertilisation guide from STERF.


How can one generate massive roots and at the same time reduce soil organic matter over time? I suggest it is impossible to do both. In the short term I can see where one can do that -- I've seen it myself. But long term, how can increasing the organic matter through production of more roots than would otherwise be produced lead to less organic matter in the soil? I'm not that credulous.