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Organic Matter and Anoxia

While preparing for our anoxia studies here at the PTRC, one trend that is speculated on in the literature is the role of organic matter (OM) in the rhizosphere and how it pertains with the accumulation of CO2 under the tarp or during ice encasement.  A small-scale pilot study was initiated to determine if there was a correlation between %O2, % CO2 and %OM.  We took cup-cutter sized samples from 5 different golf greens from 2 in-use golf courses and from our research greens here at the PTRC.  The goal of this trial was to determine if there were correlations between %OM and the accumulation of CO2 in a sealed environment.  So far the data is showing us that %OM does indeed play a role in how quickly we see a decline in O2 and an increase in CO2.  Looking at the scatterplot matrix, we can see that %OM is negatively correlated with %O2 (r=-0.85) and is positively correlated with % CO2 (r=0.79).  So what does that mean to turfgrass managers?  It appears that all the cultural practices that you do to prevent OM build-up in your greens is not only beneficial during the growing season, but may actually be helping with preventing winter injury from anoxia.  Why?  Currently the school of thought is that OM is a food source for the soil microbial community and as the food source increases so does the population of microbes that are respiring in the rhizosphere.  This increase in soil respiration rates are most likely the cause of correlation between the increase in CO2 production under tarps or during ice encasement.  We plan on repeating the experiment a second time this winter, and if we can reproduce the same correlations we may be asking for more golf courses to participate in the study next fall.  It would be great to correlate management practices with %OM and time to anoxia.  That way we could have some cold hard facts to present to our greens committees when we want to increase our OM management programs on our greens.

Scatterplot Matrix

Scatterplot_Matrix.jpg

How does Anoxia affect annual bluegrass'cold tolerance?

When turf is overwintering their metabolic rates slow down, however the plants respire in order to maintain plant viability.  During the respiration process plants use up the carbon reserves in the crown to provide energy for cellular maintenance.  Respiration requires the plant to absorb oxygen (O2) from the atmosphere and release carbon dioxide.  In an environment with constricted air flow this can lead to a potentially lethal decrease in oxygen levels.  There is speculation that this can occur under the impermeable winter cover systems that are used to prevent low-temperature injury and winter desiccation.  A controlled environment study to evaluate the effects of anoxic (no O2 available) and slightly anoxic (low O2 available) conditions on annual bluegrass commenced on December 4th 2014.  Three different atmospheric conditions were evaluated: air (20.9% O2: 0.04% CO2), 5% O2: 10% CO2, and 0% O2: 15% CO2.  One and a half 4” cup cutter plugs were placed in hermetically sealed 2L Mason Jars, and the jars were charged with their corresponding gas treatment.  Cold tolerance was evaluated on days 15, 30, 45 and 60.  The lethal temperature (LT50) of the turf was evaluated and compared statistically based on gas treatment.  The results from year one data shows that the 5:10 (O2: CO2) treatment and the air treatment had no statistical differences, while the anoxic treatment (0:15) had a reduced LT50 value.  This year one data show that cold hardiness in not affected by low (5%) O2 conditions, however once anoxic conditions are detected time for action is immediate.  With 15 days exposure to zero oxygen conditions the relative cold hardiness changed from -12C to -7C.

Day

Gas Treatment

LT50( C)

60

0:15

-2

A*

45

0:15

-4.5

B

15

0:15

-7

C

30

0:15

-7.25

C

45

air

-8

CD

30

5:10

-9.75

DE

45

5:10

-9.75

DE

60

air

-9.75

DE

30

air

-10

DE

15

5:10

-10.5

E

60

5:10

-11.75

E

15

air

-12

E

 *Temperature values not marked with the same capital letter are significantly different at P = 0.05.

Hermetically sealed jar