All across California, from front yards to farm fields and orchards, you can see patches of soil or entire fields where nothing grows.  Or better to say:  nothing is being grown, on purpose.  Circles of dirt around trees in parks and yards, strips of dirt in orchards, and fallow fields bare of vegetation through the rainy winter months.
This doesn’t happen naturally.  Nature abhors a vacuum.  A tablespoon of soil generally contains dozens of weed seeds, and others blow in from elsewhere.  A decent rain or water from a sprinkler or dripper is generally all it takes to sprout some of those seeds — which ones exactly depends on the time of year.
So how do landscapers and farmers maintain these patches of soil where no weeds grow?
The average person doesn’t know much about herbicides — weed killers — except for a single one:  Roundup.  And it’s true that Monsanto’s flagship product is the most widely used agricultural and lawncare chemical in the United States.  It’s certainly the most vilified, and was recently declared a carcinogen by the state of California.
I’ve heard people use the sentence “That soil is dead from Roundup” when describing the ubiquitous bare soil areas.  But Roundup is not the responsible party.  Roundup “kills plants, down to their roots”.  But after they die, new weeds sprout to take their place.  And that is where “pre-emergent” herbicides come in.
I’ve been farming for 25 years, and watching conventional growers farm the whole time.  But somehow it was just two years ago that I learned about pre-emergent herbicides.  These chemicals actually kill weed seeds just after they sprout, by killing their roots.  The plants never even emerge from the soil.
Conventional farmers spray these herbicides — the most common one is called Treflan — on their fields weeks or even months before planting, just below the surface.  The herbicides bind to the soil particles and stay there for over a year, or until the soil is disturbed by digging or tilling. Then they carefully plant their crops deeper than the herbicide.   If they make a mistake and put the herbicide too far down, or plant their crops too shallowly — boom, the crops die too.  If they do it right, the crops they plant will the only things growing in that field until harvest.
On organic farms, controlling weeds is a constant challenge, and a major expense.  There are definitely times when I pass conventional farm fields and wish we had some easy way of controlling weeds like they do.  And in the future there may be something — at least one company is promising to deliver an organically-approved herbicide that works “as well as Roundup”.
From a purely scientific perspective, pre-emergent herbicides are relatively “safe” for humans.  And although they are highly toxic to marine life, they don’t wash out of the soil into surface water.   I have no problem killing weeds, and we do it here all day long, in any manner of ways.  But putting a chemical into the soil that will stay there, essentially forever, and kill any plant that manages to sprout…that’s just creepy.
I guess that’s why I’m an organic farmer.