Turfgrass and Urban Soils @ UW-Madison

Fall is the time of year when surface soil temperatures cool, forcing turfgrass roots to grow deeper into the soil in search of warmth. This photo was taken the morning of Sept.  27. It shows new roots (with many root hairs) growing vigorously through the bottom of a 12 inch deep PVC pipe. The pipes are used to measure evapotranspiration and identify low water using grasses. The turf is mown at three inches with no irrigation, fertilizer, or pest control.

The picture nicely illustrates the point that fall is an important time for root growth. We have been removing these PVC pipes all year long, and did not notice any active root growth through the bottoms until now, with surface soil temperatures at  60 F and falling, and average daily air temperatures consistently below 50 F. Recently completed work in our lab revealed that nitrogen fertilization does not significantly enhance root growth in the fall, as has been largely assumed. In fact, we found some evidence the the contrary.

The best approach to encouraging deep roots in the fall is to create or foster healthy soils by minimizing disturbance during construction and managing compaction by aerification, adding organic matter, and limiting traffic — especially when the soil is wet.

Congratulations to Dan Lloyd for completing his Master’s Degree earlier this August, he’s now getting settled in at the University of Missouri as a research technician in Dr. Xi Xiong’s lab. At the UW, Dan’s research took a close look at the beneficial claims often associated with fall-applied N. He applied N (as ammonium sulfate) to different grasses in the field and in highly controlled growth chamber on either September, November, or October 15th in Madison, WI and St. Paul MN (thanks to Dr. Brian Horgan and Andy Hollman!). He came up with some pretty interesting results. For the field study, Dan found that usually less than 20% of applied N made its way into the plant for applications of 0.5 to 1.0 lbs N/M in October or November. This is in contrast to 50-100% uptake with the September applications. However, the September application resulted in growth surges that would be undesirable in many cases. We also found that N applied on October 15th in WI and MN kept the grass a nice, healthy green until snow fell — but 0.5 lbs N/M was just as good as 1.0 lbs N/M. By November, the color from the September application was fading fast and the November applications never induced a color response in fall.

During the growth chamber study,  he found that N applied in cool temperatures (Sept. – Nov.) had no positive influence on root growth or photosynthesis rate.  Dan’s work has cast some doubt on the universal conventional wisdom that late fall is the best time to fertilize. We will continue to investigate optimal timings and rates for fall applied N, but for now it seems safe to conclude that the best strategy for efficient fall fertilization is to use slow-release sources that meter N out slowly in small doses that the plant can absorb. In Wisconsin, golf course superintendents should consider skipping large fall applications on putting greens and just continue liquid “spoon feeding” every two weeks or so until mid-October. Homeowners should consider making a single application of a fertilizer with about 50% slow-release N in late September or early October.

This research found that late-fall N application are ineffcient. Good color responses can be achieved in the late fall by making small N applications and presumably by using slow-release fertilizers.

Dan with his winter gear on in June inside a cold growth chamber. In this shot, he was measuring photosynthetic rates of different grasses in response to fall-applied N

Check out the full news story on Brad Debels’s masters project at: http://www.news.wisc.edu/16933

On Thursday and Friday this week, we had the pleasure of hosing the Wisconsin Alumni Association’s “Grandparents University”. Thirty-eight kids (ages 7-11) brought their grandparents out to the research facility to learn about bugs, dirt, and grass. Everyone had a blast, and was a good chance to connect with alumni and future alumni. Fred Madison and I taught everyone about soils and different soil types on Thursday and then we got to play around in a 6 ft. deep soil pit on Friday. Check out the pictures below courtesy of Tom Schwab.

Is it drought? Sure looks like it. Actually this is a P deficiency on an A-4 bentgrass putting green. Soil test levels were adjusted prior to planting. So far, we’ve found that at least 10 ppm Mehlich-3 P is required for adequate growth. Purple, drought-looking deficiency symptoms develop rapidly below 10 ppm. However, there is essentially no difference between the plots with 11 ppm and 25 ppm. We don’t see a gradient of turf quality like we often do with N (different shades of yellow to green depending on N rate). It appears that P is more of a “light switch” nutrient. There is either enough and the grass looks great, or there is a deficiency and the turf quality declines rapidly. Also note the green “river” running through the picture below. It is the result of a leaky spray boom dripping phosphorus early this spring. Tiny drops from the leaky sprayer were enough to “turn on the switch”. This green river has remained green all year so far.

We’ve been busy preparing reports and making plot signs for the 2009 UW-Turfgrass/WTA Field Day. Should be another great event with all the latest research on display. Don’t miss out! Mail in your registration today or call Audra at 608-845-6536.

This summer, we’ve been working hard to get our 50 x 50 automated rain shelter up and running. The structure was assembled in 2008, so far this year we’ve installed a state-of-the-art individual plot controlled irrigation system. Next steps are installing the crane rail on top of which the shelter will move. This system will allow us to evaluate different grasses with very tightly controlled inputs of irrigation and precipitation.

A few weeks ago four of our five putting green mowers broke down with various unrelated issues. A normal rate of failure might for us might be one or two mowers per season. So when we had four in one day, it turned into a Kodak moment. Thanks to Chad and Dave at Blackhawk CC for lending us a mower while these were being repaired.