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October 2015
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November 2015

Two completely disparate things

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.

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.

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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.


Mineral nutrients in the leaves vs. those in the soil

Last year I shared an elemental cartogram of relative mineral nutrient amounts in turfgrass leaves. An elemental cartogram is a periodic table of the elements with the area of each element modified by a theme, and in this chart the area is modified by the amount of mineral nutrients.

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One thing I notice on the cartogram of mineral nutrients in bentgrass leaves is this: where are the micronutrients? We can see the macronutrients clearly: N, K, and P. Then the secondary nutrients: Ca, Mg, and S. But the micronutrients are in the leaves in such small concentrations that they don't register on this cartogram, in which their quantity is compared to those of the macronutrients and secondary nutrients.

The quantity of an element required as fertilizer is the difference between the amount the grass requires and the amount present. I wondered how the cartogram of elements in leaves would compare to a cartogram of nutrients in the soil. For that, I looked up the Global Soil Survey data, and generated a cartogram using the median values of the elements measured in the Global Soil Survey.

Selection_044This looks a bit different, and is illustrative of a couple things related to fertilizer. First, N is low in the soil, but the plant uses a lot of N. Comparing the two charts makes it clear why N is applied as fertilizer to most turfgrass sites. Second, K is relatively large in the cartogram for leaves, and much smaller in the cartogram for soil. Because the plant demand for K is relatively high, compared to the amount in the soil, K is often required as fertilizer. Third, Ca and Mg and some micronutrients are much higher in the soil than they are in the leaves, providing an illustration of why these elements are rarely required as fertilizer.

Waterfall charts provide a more explicit example of these calculations, but the cartograms are kind of fun to look at.


The 2015 Global Soil Survey report and data are now available

Selection_040The end of August marked 2 years of the Global Soil Survey. This report gives a summary of the results so far, shows a map of the locations -- now up to 9 countries! -- from which samples have been submitted, and announces that the survey will end on 31 December.

Thanks to all who have participated in this project for contributing samples from good performing turf at their sites. We now have a dataset which can be used for comparative analyses and as a reference for soil chemical conditions of professionally managed turfgrass.

A few related links:


This pretty much covers everything

Selection_039In January at the Northern Green Expo, I get to talk about light, water, temperature, and nitrogen. Those are the factors that influence growth, and getting the growth rate right is what greenkeeping is all about.

There are five different seminars, all linked by that common theme.

The (New) Fundamentals of Turfgrass Nutrition

Most seminars, presentations, articles, and even semester-long courses about turfgrass nutrition discuss the functions of different elements. Potassium is involved in stomatal regulation, phosphorus is essential for root development, calcium for cell wall strength, and so on. All true, but largely irrelevant for the turfgrass manager. What the turfgrass manager must know is not the function of each element, but the quantities -- is enough of this element present to meet the grass requirements, or is it not? If it isn't present in adequate quantities, how much must be added to ensure the grass has enough? In this seminar, the fundamentals of turfgrass nutrition will be explained, with a focus on an understanding of the amount of each nutrient that is required.

Nutrient Use by the Grass and Nutrient Supply by the Soil

Grass grows in soil, and nutrients used by the grass come either from the soil or from fertilizer. When the soil contains enough of an element to meet all of the grass requirements, none of that element is required as fertilizer. When the grass can use more of an element than can be supplied by the soil, that element must be applied as fertilizer. This seminar will explain how to estimate the maximum amount of an element the grass can use, how to identify the quantity that can be supplied by the soil, and how to use those two amounts to get an estimate of the amount that may be required as fertilizer.

Calculating the Fertilizer Requirement for Any Turfgrass, Anywhere

This presentation builds on the fundamentals of the turfgrass nutrition talk, and the nutrient use and nutrient supply talk, by explaining a system by which a turfgrass manager can calculate the amount of any element required by any turfgrass, under any growing condition, anywhere in the world. Some common misapprehensions about turfgrass nutrition and soil testing will also be discussed. The minimum levels for sustainable nutrition (MLSN) guidelines for interpreting soil test results, and the temperature-based turfgrass growth potential (GP), which were introduced in the two previous seminars, will be discussed in even more detail.

Soil Water Management: Timing, Amount and Syringing

Fifteen years ago, it was rare to use a soil moisture meter. Today, it seems that almost every turfgrass manager has some idea of the soil moisture content. In this presentation, Micah Woods will show that daily irrigation can use less water than infrequent irrigation, while maintaining a lower soil moisture content than deep and infrequent irrigation. Woods will explain how soil moisture meters can be used to prove that, how they can be used to measure the real evapotranspiration rate, and why syringing turf for the purpose of cooling the surface is a waste of time, water, and energy.

Instead of Shade, Let's Talk About Light

Shade from trees, buildings, clouds or mountains affects a lot of turfgrass areas, and shade can make it impossible to produce the desired turfgrass conditions. Rather than talk about the impossible, in this presentation Woods will talk about light. Specifically, he'll discuss photosynthetically active radiation (PAR), the photosynthetic photon flux density (PPFD), and the daily light integral (DLI). These sound complicated but are quite simple and can be easily measured or estimated. With an understanding and ability to measure and communicate about PAR, PPFD, and DLI, it makes it a lot easier to manage those previously impossible shade problems.

 


Monthly Turfgrass Roundup: October 2015

Here's a roundup of turfgrass articles and links from the past month:

Bill Kreuser shared a video about pigments/colorants.

You can read the abstracts of the newest turf research projects.

Not what one wants to hear after an educational conference: "as clear as mud".

Rain and fungus, a report from NCSU.

Light or temperature?

Benjamin Warren wrote about golf's urban future.

Bentgrass in hot places.

Frank Rossi spoke with Doug Soldat and Bill Kreuser on TurfNet Radio: listen when you have time.

I spoke at the Japan Turf Show. Here are my presentations.

Edwin Roald's conversation on Bogey Nights is a good listen, about golf for the modern era and lots more.

Is it necessary or advisable to apply potassium after a heavy rain? Four related posts on this.

1: I'd be applying potassium all the time, part 1.

2: part 2.

3: part 3.

4: How soil K changes over time.

This chart shows the average PPFD for every hour of the year so far, along with the DLI.

Details of the 2016 Sustainable Turfgrass Management in Asia conference announced, with registration available in January.

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For more about turfgrass management, browse articles available for download on the ATC Turfgrass Information page, subscribe to this blog by e-mail or with an RSS reader - I use Feedly, or follow asianturfgrass on Twitter. Link and article roundups from previous months are here.