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April 2011

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.

Woods_rossi_park_grass

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.


Sandcapping or topdressing: which is better?

Woods_fwy_sandcap I have often advocated sand topdressing rather than sandcapping for golf course fairways and roughs. Why? Because sandcapping at the time of construction makes for a much higher construction cost, higher maintenance cost, and invariably leads to deteriorating playability over time. Conversely, a sand topdressing program provides better playing conditions, easier maintenance, and all for a much lower cost. I am not referring to drainage. Drainage is required for both a sandcapped system and a topdressed system. But sandcapping is not drainage.

Sandcapping a turfgrass area with 10 to 15 cm of sand has a high upfront cost and then forces higher maintenance costs as well, for that sandy rootzone will require more fertilizer, more irrigation water, and more surface organic matter management than would an area not sandcapped. And what happens if the organic matter is not controlled? See below. What used to be a fine zoysiagrass is now a mixture of cowgrass and sedges. A layer of organic matter built up at the surface creates a perfect growing environment for weeds that thrive in wet soils. And all that sand underneath? One might as well bury money in the ground. Once the organic layer builds up over the sand, there is no benefit whatsoever to having the sandcap.

Sandcap
Dr. Alec Kowalewski has recently published some intriguing articles that show just how effective sand topdressing can be as an alternative to sandcapping. Not only does he demonstrate the substantial cost benefits of a topdressing (or built-up over time sandcap) program compared to a sandcap installed at the time of construction, his research also shows how turf quality improves and drain line spacing can be extended when a topdressing program is implemented. 

"Preliminary findings from this research," he wrote, "suggest that as little as 1/2” (1.25 cm) of sand can be used to improve athletic field playability by substantially decreasing the surface moisture content." His results show that once 2.5 cm of topdressing sand has been applied, drain line spacing at 3.9 meters provided sufficient drainage and surface stability. After a 5 cm topdressing layer was established, and assuming surface slope is at 1% or greater, then drain line spacing could be extended to more than 6 meters while still producing the desired surface conditions.

For full details, see:

Kowalewski, A. R.; Crum, J. R.; Rogers, J. N. III. 2010. The built-up sand-capped athletic field system. MSU Turfgrass Science Program. April 7. p. 1-7.

Kowalewski, A. R., J. N. III Rogers, J. R. Crum, and J. C. Dunne. 2010. Sand topdressing applications improve shear strength and turfgrass density on trafficked athletic fields. HortTechnology. 20(5):p. 867-872.

Kowalewski, A. R., J.R. Crum, J. N. III Rogers, and J. C. Dunne. 2011. Improving native soil athletic fields with intercept drain tile installation and subsequent sand topdressing applications. Soil Sci. 176(3): p. 143-149.

Ballmark With sandcapping at the time of construction there is a high upfront cost, turfgrass and playing conditions that deteriorate, and there will be the need for a disruptive and costly renovation to remove the organic layer that will invariably develop at the surface. Planting grass onto native soils and then topdressing with sand results in lower construction costs, lower maintenance costs, and better playing conditions over time with longer intervals between disruptive renovation projects. It is the surface conditions that matter for the playing of sports on grass, and topdressing with sand is a proven method to create the desired surface conditions.