These things aren't related, except as a follow-up to podcasts I listened to. The topics on my mind: synthetic nitrogen and soil carbon, and disagreeing with some stuff.
I recently enjoyed listening to these TurfNet Radio podcasts. I think you will too.
- The Turfgrass Zealot Project, Wilber, Tritabaugh, and Hess
- Frankly Speaking, Rossi and Koppenhaver
- Frankly Speaking, Rossi and Branham
Dave Wilber, in his monologue, mentioned that he "disagrees with some stuff" that I've been working on. I'm interested to have that conversation with him. Can you guess what it is that we may disagree about? I can, but I don't think the details will come out until we talk.
I'd usually say, the wonderful thing about blogs, and comments, is that one can respond and disagree and make corrections and arguments almost in real time, without waiting, and I was going to ask Dave to please do that. But I think he must have a good reason for waiting to give the details of his disagreement, plus it leads to more anticipation for that forthcoming podcast!
And it reminds me of something I disagree with, and that I was disappointed to see, and that I will go ahead and share. It ties in with the "clear as mud" comment from Mark Hunt after seminars at GIS this year. I'm disappointed when I hear those kind of comments, especially when the topic is turf nutrition, because I don't think turf nutrition needs to be complicated, and I think it is unfortunate that seminars can leave someone with that impression.
I didn't go to GIS this year, but I was glad to see so many of the presentations made available for download on the GCSAA website. I wish more presentations were shared. By the way, most of my presentation slides from the past few years are available at SlideShare, SpeakerDeck, or through the /seminar tag on the blog. When those GIS presentations were available, I downloaded and read the ones I was interested in, most especially The Knowns and Unknowns of Nutrient Uptake by Roch Gaussoin. There is a lot of valuable information in that presentation, and lots of things I agree with, but one statement on slide 44 can't possibly be right.
The statement I refer to is this: even if there is an optimum level of nutrients in the root zone, it may not be readily available. If that statement were true, then by definition there is not an optimum level of nutrients.
So that's something I disagree with. I look forward to a discussion with Dave Wilber in due time to see which of the things I've been working on are ones he disagrees with. By clearing up all the disagreements, we should move closer to the right understanding.
The second topic was discussed when Frank Rossi spoke with Bruce Branham. It relates to the N source, and the question is, when inorganic N is added to turfgrass, does that cause an increase or a decrease in soil organic matter/soil carbon? I also had a question about this from Ben Polimer:
You can listen to Rossi and Branham discuss this topic in a lot more detail. I have three thoughts on the matter.
1. The research in question is on field crops, not grassland. Turfgrass systems are different. Soil carbon probably doesn't increase forever under turfgrass, but after establishing turf, the soil carbon is expected to increase for some years.
2. It seems that inorganic N applied to turfgrass causes an increase in soil organic matter. If inorganic N addition reduced organic matter, one could solve thatch problems and eliminate the need for coring and reduce the sand topdressing requirement by adding inorganic N fertilizer.
3. Data from Table 3 in Hopkins et al. (2008) are plotted above. The plot shows soil organic carbon from selected subplots of the Park Grass experiment receiving different fertilizer treatments, with the soil organic carbon measured in 1876, 1959, and 2002. Park Grass is not turfgrass, but it is permanent grassland, cut for hay twice per year. In a comparison of soil organic carbon from samples collected in 1872, 1959, and 2002, one can see that the addition of inorganic N fertilizer -- ammonium sulfate -- to plots 18d and 1d has led to increased soil organic carbon compared to those plots that have not received inorganic nitrogen.