Viridescent - the Asian Turfgrass Center blog

Calcium for Turfgrass: is there enough in the soil?

The answer, almost certainly, is yes. These calculations of how much calcium the grass uses, compared to how much plant-available calcium is in the soil, leave little doubt that there is almost always more than enough calcium in the soil to meet the needs of the grass.

How much calcium does grass use?

Let's take a turfgrass site at which clippings are removed, and estimate how much calcium is removed, or harvested, in one year. A reasonable estimate for annual clipping yield of maintained turfgrass is about 400 g m^-2. A reasonable estimate for calcium in the dry matter of turfgrass clippings is about 4500 ppm = 4.5 g kg^-1 = 0.45%. So if we harvest, over the course of a year, 400 grams of clippings from each square meter, and if those clippings contain on average 0.45% calcium, then the mass of calcium harvested from one square meter each year is:

400 g x 0.0045 = 1.8 grams of calcium removed each year

How much calcium is in the soil?

We've just calculated that in the situation where we remove the clippings from a maintained turfgrass area, we may be removing about 1.8 grams of calcium from each square meter each year. Let's now imagine that our root system is 10 cm deep, and that the bulk density of the soil is 1.5 g cm^-3. In one square meter, then, to a depth of 10 cm, we have a volume of 100 L, and a mass of 150 kg. Let's say this is a sandy soil, with a relatively low cation exchange capacity, and that the plant-available calcium (the calcium that is in soil solution and on cation exchange sites) is at a concentration of 400 ppm = 400 mg kg^-1. How much calcium is that?

150 kg of soil x 400 mg/kg = 60,000 mg of calcium = 60 g of calcium

Three Decades

That's how long it would take, 33.3 years, to be precise, for the grass to use 60 grams of calcium if harvested at the rate of 1.8 grams of calcium per year. There is much more calcium in the soil than is required for healthy turfgrass, even in soils that have relatively low amounts of calcium.

Chemical Fertilizer Programs for Sand Based Rootzones - the 1 minute version

Last week at the Tennessee Turfgrass Association conference I gave a 30 minute presentation with the title Chemical Fertilizer Programs for Sand Based Rootzones. But this topic doesn't always require 30 minutes to explain - I like to distill this topic into the most important principles. There is plenty of experimental and empirical evidence to show that these four principles, if followed, will give excellent results.

1. Apply the right amount of nitrogen
2. Ensure soil pH is more than 5.5 and less than 8.3
3. Ensure soil potassium (as measured by the Mehlich 3 extractant) is kept above 50 ppm
4. Ensure soil phosphorus (as measured by the Mehlich 3 extractant) is kept above 35 ppm

The End (of the 1 minute version of this topic)

If you are especially interested in mineral nutrition for turfgrass or soil nutrient analysis for sand rootzones, you may want to read or watch some of these more lengthy expositions.

Simple Fertilization: Use the Nutrients Already in the Soil, from the Hawaii GCSA newsletter

PACE Turf Potassium Sufficiency Video, on Youtube

Soil Testing: It Does Not Have to be Difficult, on Youtube

Creating an Excellent Playing Surface: Managing the Plant, especially section 2 regarding nitrogen application

Does Potassium Fertilizer Really Increase Roots?, from TurfNet Monthly

And for those who really want to reduce P and K, consider the implications of The Park Grass Experiment and the Fight Against Dogma, written with Dr. Frank Rossi and published in the USGA Green Section Record

Potassium for Turfgrass: interview with Dr. Larry Stowell of PACE Turf

Dr. Larry Stowell and I recorded this video interview about potassium fertilizer for turfgrass. How much potassium is enough? How should you decide how much potassium to apply to meet the plant requirements, without wasting money by applying too much? Is potassium fertilizer necessary at all? Watch this video to find out, and check out PACE Turf for a wealth of valuable turfgrass information.

Why "Liquid" Fertilization is Better Terminology than "Foliar" Fertilization

When applying fertilizer to turfgrass plants, there are two general types of application: liquid and granular. Granular products are applied in a dry form, while liquid products are applied as a spray application.

The term foliar fertilization is often used to describe liquid applications made to the leaves, or foliage, of turfgrass. But this can be misleading,with the implication that all the applied fertilizer is being taken up by the foliage. 

The reality is that only about 50% of the fertilizer applied to turfgrass foliage enters the plant through the leaves. And in many cases much less than 50% is absorbed by the leaves. Recent research by Branham et al. found that 14 to 37% of the applied nitrogen was taken up by turfgrass leaves in Illinois. Research at Arkansas by Stiegler et al. found uptake of 36 to 69% of foliar-applied nitrogen. These results are similar to the experimental results of Professor Jörg Schönherr who has done extensive research into foliar uptake of nutrient ions. Uptake is the highest at 100% humidity, so once the liquid solution has dried on the leaf, foliar uptake of the applied nutrients ceases. 

Even with the limited foliar uptake, I still prefer liquid applications to granular applications. With liquid applications, precise doses of nutrients can be spread evenly at low rates to all areas of the sward. It is impossible to get such even distribution of nutrients when applying granular products. 

When I was the superintendent at Shanghai Links, we made liquid fertilizer applications to all areas of the course as the main source of nutrients. We would allow the fertilizer to dry on the leaves, so we would get some uptake by the foliage, and we would then apply enough water to rinse the remaining fertilizer from the leaves and into the upper reaches of the soil, where the remaining nutrients could be absorbed by the roots.  

Ten Years Ago on a Golf Course in Japan: part 1

I was a golf course superintendent in Japan from September 2000 until August 2001. Now, ten years later, it is interesting to see some of the photos from that year and to remember what it was like. We were working with a maintenance crew of about sixteen people in July of 2001, and I think five people on the crew went on to be golf course superintendents themselves; two interns from the United States, and three of the Japanese crew. 

We had a great team. July 22 was a Sunday that year, and on Japanese courses then, it was not typical to have much afternoon or "twilight" play. Golf tended to be (and generally still is) a structured event, so tee times (Japanese courses usually do a two tee start, off #1 and #10) would generally be booked a few weeks in advance, with the last tee times usually set at midday. Even on a busy day, after 14:00 or so the course would begin to clear as the last golfers played their final nine holes. 

We were able to get a lot of work done on these afternoons. Soil tests of the fairways showed that the soils were low in magnesium and potassium. We were able to find sul-po-mag (0-0-22) from a Japanese agricultural supply company and apply it to fairways to increase the potassium and magnesium availability. And we had to do a lot of work to manage soil compaction, improve water infiltration, and stimulate growth on the bermudagrass fairways. At the time Habu CC was one of the few courses in Japan that used two passenger carts, and at which the carts were allowed to be driven on the fairways. We were doing about 4,000 rounds per month, all with carts driving onto narrow fairways of this course in the mountains of Chiba. So ten years ago today, we waited until the last golfers had moved off these holes and then worked until the sun went down.

What's the Most Accurate Way to Measure Available Nutrients in the Soil?

Have you seen this picture before? I used this photo in the announcement for turf science seminars I gave at Japan last winter, and a golf course superintendent asked me this week about what is shown in this photo. This is a cation exchange membrane in general, and is specifically a PRS (Plant Root Simulator) probe from Western Ag Innovations. In my research at Cornell University, I used these exchange membranes to measure potassium flux in the soil. 

The results of this experiment were summarized in a paper we published in Applied Turfgrass Science. Exchange membranes are quite sensitive to changes in nutrient supply, and one could make a strong case for exchange membranes being a more accurate way to measure the really available nutrients in the soil compared with conventional soil testing techniques. Potassium supply to the roots, for instance, is affected by the activity of K⁺ in soil solution, leaching, soil temperature, soil water content, root uptake of K⁺, release of K⁺ from mineral forms in the soil, and other contributing factors. Exchange membranes, by measuring the nutrient flux over time, are able to capture much of the true variabiability in nutrient supply, similar to what grass roots would experience.

In our experiment, we found that the very sensitivity and accuracy of the exchange membranes makes them less practically useful than a conventional soil test in predicting whether potassium should be applied or not. To summarize the results of our experiments with cation exchange membranes, we found that:

1. Potassium supply increases when potassium fertilizer is applied.
2. The effects of potassium fertilizer can be long-lasting, even in a sand with low CEC (1.2 cmol_c kg^-1). We detected increases in potassium supply rate six months after an application had been made. I think most people would expect the potassium to leach or otherwise have no effect on supply rate six months after application in a low CEC sand.
3. Potassium supply rate can be sufficient to meet plant requirements in many sands because of potassium release from mineral forms in the soil.

How Much Potassium Does Turfgrass Need?

Potassium is the mineral element found in the second-highest concentration in turfgrass leaves; only nitrogen is at a higher concentration. But how much potassium fertilizer is enough? Dr. Doug Soldat from the University of Wisconsin wrote a post for the Turf Diseases website entitled How I'd Manage Potassium on Cool-season Turf, and he has expanded on that in an excellent article in the May/June issue of The Grass Roots.

Dr. Soldat makes a quick review of when and how potassium is likely to provide improved cold, heat, drought, and wear stress. You might be surprised to find that the research results aren't very strong or conclusive in supporting the idea that high levels of potassium fertilization confer these increased stress tolerances to cool-season grasses. There is no doubt that potassium is an important mineral element, but if there is already enough potassium available to the grass, adding more doesn't seem to have much of an effect. For example, we can read in textbooks that more potassium will lead to a more extensive root system, but is that really the case? 

Does potassium fertilizer really increase roots?, I asked, in this article from TurfNet Monthly. My conclusion was that potassium fertilizer will do nothing to increase roots, and in fact may actually cause a decrease in rooting, unless the potassium was being applied to correct a potassium deficiency. Potassium application to turfgrass is likely to increase rooting only when it eleminates a potassium deficiency. I would classify a turfgrass soil as requiring additional potassium at about the 50 ppm level using the Mehlich 3 soil test extractant. If the soil is less than 50 ppm potassium, we might expect some response from a potassium fertilizer application. If the soil has more than 50 ppm potassium, the grass can almost certainly get all the potassium fertilizer it requires from the potassium that is already in the soil, and potassium fertilizer would be unlikely to influence turfgrass performance. 

New Information on Diseases and Cation Exchange Capacity

I've been really busy in the past month, returning to Thailand after the exciting Masters Tournament, traveling to Singapore, Vietnam, and Sri Lanka, studying, and writing. Thanks to @daisukeiw who sent me the image above of the layout for my new series in Golf Course Seminar magazine. Pitchcare Oceania have just published a panel report on cation exchange capacity (CEC) and have featured some comments from me about CEC in sand rootzones and how it can be estimated most accurately by using an equation in which the only variables are soil pH and soil organic matter content.

I've also made some international updates to the Turf Diseases website. Some of my recent posts on that site are:

Large Patch Resistance of Zoysia?

A Cornucopia of Disease in Southeast Asia

Healthy Grass = Little Disease

Potassium, Hokkaido, and Snow Mold

Turfgrass Diseases in India

What is the Most Interesting Disease in the World?

Mites, a Corpse Plant, and Native Grasses

Large Patch on Zoysiagrass

More About Seashore Paspalum

A Most Unsightly Disease

The Wow Factor, Seashore Paspalum, and Dollar Spot

Fertilizer and Weeds at Park Grass

An article I wrote with Dr. Frank Rossi about the Park Grass experiment at Rothamsted has recently been published in the USGA Green Section Record. (Download the article here). This experiment has been ongoing for more than 150 years and it involves fertilizer treatments applied to grassland and the many measurements that have been made over the years on the experimental plots. One of these measurements is the botanical composition of the plots, and the results are amazing.

When nitrogen in the form of ammonium sulfate is applied as the only fertilizer, finer grasses predominate and weeds are not present. When potassium is applied, dandelions and other weeds proliferate. Lime also causes an increase in weedy species. 

The recommendations for complete fertilizers along with lime treatments that are commonly made for for cool-season lawns and other general turf areas are probably contributing to an increase in weed abundance as well. Is it possible that less fertilizer could also lead to less weeds and less herbicide use? That is certainly something to consider, and Dr. Rossi and I suggest that the results of the Park Grass experiment are worthy of further attention from turfgrass managers.

Why I Study Japanese

There are two monthly magazines that go to almost every golf course in Japan. One is Golf Course Seminar, published by Golf Digest Japan, for which I write a column about turfgrass science; the other is Monthly Golf Management, published by Ikki-Web, who also produce the annual Greenkeeper almanac. The Greenkeeper 2011 has five sections, the first three being reviews of major tournament preparations, what appears to be a turf science quiz, and reviews of some turf science meetings held at Japan in 2010.

It is the final two sections that make up 80% of this 358 page book, and these are the sections that I find the most interesting, and that I can, with my rudimentary Japanese, understand to some extent. These sections include the fertilizer and pesticide and mowing programs (and much much more), giving the entire maintenance schedule, really, for 26 golf courses, and then a Golf Course Data File with general information, including grass types down to variety, for 949 courses at Japan.

What specifically do I find most interesting in this book?

1. The very fact that it is published, that there is a demand for such data, that the publishers go to the effort to compile it and print it, and that so many golf courses share the information.

2. The huge variations in fertilizer application ratios and timing. Some courses are using less than 10 g N m^-2 per year for creeping bentgrass in a growing environment in which I believe 15 to 20 g N m^-2 are required. Some have an N-P-K ratio of approximately 8:1:8, which I understand, or 8:1:4, which I think in most situations would be optimum, and some have approximately 8:1:16, which I think is too much K, but I understand that also. Then there are those with approximately 1:1:1 ratios, or 3:4:2 ratios, and then I wonder what those greenkeepers are trying to accomplish by applying so much phosphorus. Or the course applying just over 6 g N m^-2 annually, but more than 13 g Mg m^-2? Why? Or how about 33 g Ca m^-2 and 1 g Mg m^-2? That is a 30:1 ratio, but in the grass Ca and Mg will have a nearly 2:1 ratio.

3. The mowing heights and number of greens mowing events are given by month, and I find it interesting that at a particular course with an unusual fertilizer ratio, the putting greens were mown 31 times in July, 16 times in August, and only 9 times in September. Did the fertilizer applications have anything to do with that? This is voyeuristic, I know, but for a turfgrass scientist who is interested in the practical aspects of turfgrass maintenance, I find it fascinating to have all this information in front of me and it gives me a tremendous number of ideas for information to discuss in training programs or magazine articles or even research projects or consulting programs.

4. I may be completely missing it, but I see nothing in the course data guides about what the soil pH or nutrient levels are, nor anything about soil organic matter content, nor anything about irrigation water quality. For some reason, these types of data are given much more weight in the United States.

5. Penncross is the preponderant bentgrass variety growing on putting greens. There are 949 facilities listed in Section 5, the Golf Course Data File. This represents nearly half the golf courses in Japan. Of these, 649 have Penncross greens.

6. The book is fascinating but seems to be lacking something that greenkeepers can actually use to help them improve playing conditions. The book is 358 pages packed full of data about golf course operations, and specifically grass types used and maintenance practices employed, on golf courses in Japan. Yet the information is, to some extent, of little practical use, because it is all passive, just in a book; it is not necessarily correct — writing out the detailed maintenance program for a course does not necessarily mean it is a correct program or one that should be copied; and for a greenkeeper who is managing Penncross, it may be of some solace to know that so many others are also managing the same grass, but it doesn't change the fact that almost any variety other than Penncross would have better performance in Japan.

Still, it is fascinating, and I look forward to seeing The Greenkeeper when it is published each fall, and it is books such as this that make me wish I knew more Japanese.