Goosegrass and Compaction

I have been working on goosegrass biology and control for a couple years and I found this article previously published in turfgrass trends.  The article is title “Goosegrass Shows No Tolerance to Compaction.”  Not to bemoan the work– it is good work, but it misses a few crucial points.

First, just because a plant declines in measured variables does not mean it does not tolerate the condition.  Lots of weeds/plants in general will decline in root growth and general biomass when under a stress– such as compaction or low fertility.  Such species are not “obligate” to the condition they are “facultative”.  In other words, the species does not necessarily like the conditions, but they tolerate it in order to survive.

Second, tolerance to a condition is better measured in terms of fecundity– especially with an annual species.  Fecundity is simply reproductive success.  So if it produces seed, even if lower than normal amounts it can “tolerate” the conditions.

Third, goosegrass does not have to have similar rates of growth and development when compared to compacted and not compacted, it just has to have less in a decline than the species it is competing with.  It is like the joke- if we are being chased by a lion, I don’t have to out run the lion, I just have to out run you.

The full scientific paper – Goosegrass and Bermudagrass Competition under Compaction — was published in Crop Science in 2009.  Very well written article but it basically says the same thing– goosegrass does not tolerate compaction.  I have to disagree with their assessment– one problem is they did all their studies in high sand soils — almost pure sand and a 91% sand native soil.  Second, compaction can vary with soil depth.  In a sand soil, compaction can occur at the surface layer but traffic may not cause compaction at lower depth.  Another problem is that I cannot find where they reported where they got their goosegrass seed for the study.  There are definite ecotypes of goosegrass that have been selected for greater compaction tolerance just like there is herbicide resistance selection.

Certainly I have a bias since I find goosegrass being the only species that will survive in highly compacted, concrete type soil.  I will post goosegrass growing in strange places later.



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