Those actinomycetes sure do smell good.

Here in ATX, it rained the other day.  And boy-oh-boy did it smell wonderfully refreshing.  It reminded me of a much-maligned kingdom (or domain, depending one what taxonomic ranking system you use): bacteria!  Although bacteria can get a bad rap, we can thank them (particularly the actinomycetes) for one reason behind that fresh rain smell.

Here are some potential causes of our odoriferous joy:  

• ozone from a thunderstorm,
• petrichor  (click here to read multitudinous gargantuan technical words), and
• geosmin, which is produced by the Streptomyces bacteria, a genus within the group actinomycetes!
• Factoid: It is a type of terpene (we've discussed terpenes before).
• Factoid: It can give fish an unpalatable flavor.  
• AWESOME factoid: Wild Bactrian camels may be able to smell water up to 50 miles away because they can smell geosmin.  Thank you soil bacteria for helping the thirsty camels!!

Do you learn by listening? Listen here for an easy to understand explanation, covering the same stuff mentioned above. 

Besides that wonderful smell, there are other reasons why actinomycetes are awesome.  I imagine you've heard that bacteria such as rhizobium help legumes obtain nitrogen from the air.  Well, the actinomycetes genus Frankia helps non-legumes fix nitrogen from the air.  This means that they can help plants colonize infertile and newly forming soils.  Also, many actinomycetes can digest what others can't.  Those hard to decompose substrates such as chitin and cellulose are prime picking for these guys.  That is great news for compost with sawdust and branches!

Want more actinomycetes?  They can tolerate arid and salt-affected soils.  They work best in soils with a pH between 6.0 - 7.5, but are more sensitive to acidic soils.  Don't worry too much about acidity though, since fungi can take over the decay where actinomycetes leave off (info also from reference #1).

Also, this great article says that daily turning of compost, while good for some purposes, can inhibit growth of actinomycetes.  Although actinomycetes can either be mesophilic* or thermophilic*, they are mostly known to work in the later, cooler stages of compost creation.  If you see something that looks like gray spider webs in the outer edges of your compost, it just might be actinomycetes.  Please remember to say, "thank you!"  

Please enjoy your "rain smell" responsibly.

*Definiciones:

Mesophilic: microbes that function at temperatures above 113 °F

Thermophilic: microbes that function at temperatures between 50-113 °F (10-45 °C) (ref)

Basic soil physics lesson plan up and running

Hey guys,
I'd like share a lesson plan with you that I wrote for school-aged kids.  I don't see a way to post a PDF on blogspot, so I put it up here instead.  It is about one of my favorite soil topics- soil porosity and water storage!  After you read it, you can consider yourself better versed in basic soil physics!

Thoughts on the lesson plan? I'm thinking of writing up more, in hopes that I can put them to use in "real life" one day.
Thanks!
Amanda

UPDATE!  This USGS link is awesome and also teaches us about capillary action.

An even smaller snake?

I had no idea they would just get smaller.  Yes, you are using my fingerprints for scale!!

That, according to my hubsy a bona fide herpetologist, is a Texas Blind Snake (Leptotyphlops dulcis).   Another fossorial snake, a burrower.  According to Bastiaan M. Drees of Texas A&M, this little guy indicates a healthy environment. Quoting him, they eat "larvae and pupae of insects, termites, and earthworms."  

In a way, he/she reminds us how intimately we depend on soil.  For example, their residence in the soil seems to be partly determined by soil moisture.  They like it, but of course sometimes it floods them out.   This page says that they move deeper underground when the surface soil dries out in the summer, and this page says that they are spotted more easily after a rain (like today, what a coincidence).  I imagine it's cuz their burrows got plugged with el agua.  Soil moisture reminds me of a lesson plan that I want to share with y'all, but I don't know how to put PDFs on here....

Anyways, they are nice guys.  They stay small, don't bite the homo sapiens, and they eat garden pests.  Let's keep him!

If you want to read about the more gruesome aspects of their hunting style, and reads words like "chemoreception," click here.  

Are y'all encountering some awesome soil creatures as well?

This snake

This snake came out to play as we were ripping up some invasive jasmine for a new chicken play yard.  He and his cousins were out en masse!  He is a rough earth snake (Virginia striatula), a native in this area, and he eats earthworms almost exclusively.  


At first I was sad to learn that this guy eats one of our most beloved and useful soil friends. Earthworms are what we call a keystone species, because they are almost exclusively responsible for their function in the soil- creating aeration macropores.  Macropores are an important part of healthy soil structure (more here and here).  But then I turned that frown upside down when I realized the implications. We must have a TON of earthworms if their population is sustaining a huge number of rough earth snakes.  Yay!

Rough earth snake facts (from here):

• They are fossorial (live underground), and viviparous (give birth to live leetle baby snakey-poos).

More worms facts:

• There are over 7,000 different species of earthworms around the world.
• They like soil with lot of calcium for their slime production (we've got that here, my soil was formed from calcareous clays and marls), and moist, well aerated soil with ground cover (like that invasive jasmine we just killed,oops).
• They are sensitive to salinity, sandy soils, ammonia fertilizers, carbomate insecticides (and others), and sudden heavy frosts on unprotected (unmulched or otherwise covered) soils.  Tillage is the WORST for them, and their population will suffer dramatically from this.
• This web page is awesome for kids and adults.  The lesson talks about how worms can adapt to different soils and temperatures.  Also, it tells us that some of our U.S. worms may not be native! They probably came over from Europe, along with their fellow homo sapien immigrants.   

Biodiversity factoids:

• Many scientists believe that there are more species below our feet than above them.  
• Forested soils generally house a larger diversity of soil animals (fauna) and more fungal-dominated microflora than grasslands, but
• grasslands support greater soil faunal mass per unit area with higher activity (measured as more CO2 generated through respiration) than forested areas.
• Tilling reduces habitat for soil animals, and cultivated fields have fewer soil organisms and lower soil organism biomass.

(Worms and biodiversity facts from reference #1)

The Skinny on Pine Needles

Pine needles were recently thrust into my consciousness by two friends. So, if you don't mind, let's discuss the skinny on pine needles, shall we?

But before we delve, side note! I did learn one consideration in its sustainability of use during my internet perusing.  Harvesting pine needles off the ground, like harvesting any other crop, ultimately reduces the nutrients in the soil, so conscientious pine needle collectors may want to give something back for the taking.

Moving on, did you know how awesome they are? They are a pretty good mulch! Look at all these reasons! Particularly on hillsides, since they interconnect with each other and stay put. But many people believe that pine needles, as mulch, add acidity. Perhaps they read this link (look under wheat straw). But what if you didn't think it was acidic at all, because you read this link? Or what if you were like, who cares, I read this pine needle apologist! So I asked the expert who wrote this, where he originally writes that pine needles should be put on acid-loving plants. He is Dr. Don Rakow, Executive director of Cornell Plantations at Cornell. He explained his text succinctly:

Pine needles have been shown to be slightly acidic, usually in the range of pH 6.0 – 6.5. This is not very different from average rainfall pH. The acidity is related to the presence of hydrogen ions in the volatile terpenes in the needles. For a review of a somewhat rigorous series of experiments that examined this subject, check out: Pine Straw (Pine Needle) Mulch Acidity: Separating Fact From Fiction Through Analytical Testing by Scott Jacobs.

So there you have it, it is acidic, but only temporarily and not enough to worry about. So all the supposedly conflicting information from reliable sources out there, were all right in their own way. So I guess this is another YES WE CAN, agree moment, heee.

By the way, you may be curious about terpenes.  They are "compounds produced by plants from isoprene, a hydrocarbon that has its five carbon atoms arranged in a branched chain." They smell really good, and in the leaves of a conifer tree suffering from air pollution, they change in chemical composition and amount (more evocative terpene-talk here, from where I got this info). Wow.

Pine needles by any other name would still smell like terpenes.

(P.S. One day I'll read the instruction manual on my camera, and maybe get a better pic for you)
(P.P.S. Speaking of soil myths and mulch, here are some interesting tidbits on mulch selection from an Australian soil blogger)