Hey folks I hope you're doing well today.
I'm going to be talking about cover crop nitrogen scavenging credits that farmer in the central coast region of California
can get as part of this new regulation called Ag. order 4.0.
I'm really excited to share with
you some of our research results because I think
it's really going to help farmers to get these
credits in a much easier way than we knew about say even a year ago.
So I'm going to focus on three main things. First I'll talk about the different types of cover crop nitrogen scavenging credits
and then I'll talk a little bit about the research
that we did to help farmers get the credits.
And then lastly I'll walk you through a scenario of exactly how a farmer would get that credit.
All right now let's keep in mind that cover cropping with non-legumes in these systems
is considered a best management practice because itﾠ
can help us to reduce nutrient losses especially
nitrogen losses down into the aquifers.
There are some other benefits to soil Improvement and many other things from
growing cover crops also
Here's a table that I put together that talks about these credits or these incentives that's why the carrots are there.
So there's a standard cover crop credit
which is a smaller incentive a smaller carrot, and then there's the calculated credit which is
a much bigger incentive
Now the way that they're similar is that they both require the cover crop
be a non-legume and that the cover crop be grown from October to April for at least 90 days.
And then it also provides or produces a shoot biomass
of four and a half thousand pounds per acre of oven dry biomass.
Now the way they differ is that the calculated credit which is the bigger carrot
the bigger incentive that also has a carbon to
nitrogen ratio requirement of 20 to 1 or more.
All right so the goals of this research were to
try to develop methods where we could estimate
cover crop shoot biomass
and carbon to nitrogen ratio
without the farmer having to send anything off to a laboratory or do other complicated analyzes.
So what we're trying to come up with are simple and fast,
and relatively accurate methods,
that are farmer-friendly and field-based.
Ones that you can go out into the field
take some measurements and you'll know right then and there
you've met the requirement or you haven't met the requirement, you need to wait another weekor so.
So things like that.
So to try to address this we did research from Santa Barbara County
up through Monterey County and then to Santa Cruz County.
And our research collected nearly 300 samples.
It came from organic farms, conventional Farms,
also from five replicated trials at the USDA organic research farm where I work.
And these were mainly focused on overwintered cover crops, but we also had some summer and fall cover crops in there.
The cover crops we focused on were Merced rye on the left here and Pacheco triticale.
You can see Merced rye tends to close its canopy faster than Pacheco triticale does.
And here the cover crops are a little bit later as they're starting to get
some height to them, and then this is quite a bit
later in the season when they're actually getting
close to where they could actually set some viable seed.
So a farmer wouldn't usually let their cover
crop get this this old but I just wanted to show
you how they look different. So Merced rye is quite
a bit taller than Pacheco triticale is.
Alright so here's a really really nice graph. I love this
figure because what it shows us is that we can
estimate shoot biomass from shoot length. So this
is a figure for Merced rye. Let me orient you a little bit. So here's the shoot length
on the x-axis in centimeters or on the upper one in inches. And then on the y-axis we have
oven dry shoot biomass in kilograms per hectare or pounds per acre.
and you can see here's the
Ag. Order requirement of 4500 pounds and you can see as the shoot length
goes up the biomass goes up also.
So Merced rye needs to have a biomass or shoot length I should say
of about 31 inches in order to hit the Ag. Order requirement for its biomass.
Now here's the same thing for Pacheco triticale, for it to
hit the biomass requirement it only has to be
about 27 inches tall. What you can see with both
of these cover crops is that shoot length is an
excellent way to predict oven dry biomass.
So that was a real nice finding from our research.
A little bit about shoot length. Now so cover crops
like cereals like this they produce many different
stems, we call these the side ones, we call those tillers.
When I'm talking about shoot length I'm focused on the main stem shoot length and soﾠ
we are actually measuring the length of that
main stem as if it was completely straightened out
and the reason for that is that when you go out to
sample a field you often will find plants some
of them are straight up other ones are crooked
and all over the place, so our measurement was
focused on the the shoot length of the main stem
as if it was completely straightened out.
I'll make another video with more details on this.
So how would a farmer go out there and measure their field so that they can get their biomass estimate?
What I would suggest so here's an example with a Merced rye field and a Pacheco triticale
field, and what I would suggest is a farmer go
out there, you walk a diagonal across the field
and you take 10 samples.
At each point along that sampling area you'd put you'd put your hand down
to the ground,
you'd put your hand around some plants,
you'd dig them up,
and then you randomly choose one of the plants.
You put it in a bag
and bring those 10 plants out
of the field and you're ready to measure your
the length of the main stem on each of those 10 plants.
You're also going to use those 10 plants
to do something else you're going to estimate the carbon to nitrogen ratio
and what we're going to do to try to get a good number on this
is we're going to use this thing called the Feekes scale.
It's a growth stage scale for
tracking the development of cereal crops it's widely used throughout the United States.
And what it does is it gives us a number from 1 all the way up to 11
for the different stages from the seedling stage to tillering to stem elongation
you know heading out and then flowering and then grain filling and ripening.
So what we found is that the Feekes growth stage
is an excellent way to estimate the carbon to nitrogen ratio of the cover crop.
So here's a graph for Merced rye.
And we've got the Feekes scale here on the bottom on the x-axis,
then we've got the carbon to nitrogen ratio here so you can see there's the 20 to 1 number
for the Ag. Order that's required
and notice that our fitted regression curve this black line here
that crosses that requirement of the Ag. Order right about Feekes 9.
So we can use Feekes 9
as an indicator of when the carbon to nitrogen ratio requirement has been met
for both Merced rye
and here it is again for Pacheco triticale.
See it crosses right around 9.
So this is very exciting
because we can use this and farmers hopefully find it quite helpful.
I'm going to walk you through now a scenario
for how a farmer would be able to get this calculated nitrogen scavenging credit for a
Merced Rye cover crop like what you can see right here.
Let me give you a little bit of information. So this is a cover crop, let's just say it was
planted in October 15th
92 days after planting it was sampled so it meant that 90-day requirement.
So the shoot length 36 inches the Feekes growth stage is 10.
So what we first need to do is we need to estimate the amount of oven dry biomass.
and we're going to do that using these this table from the Ag. Order.
Now this table is based on this figure that I showed you earlier.
And what you can see for a average shoot length of 36 inches
here's our biomass in pounds per acre.
So we put that on our little sheet here.
Now we need to get a table for the carbon to nitrogen ratio.
So we can see we've got a here's a table with the Feekes scale
and then we've got our estimated carbon to nitrogen ratio
as well as the estimated nitrogen concentration.
So for a Feekes growth stage of 10 which is actually above what's required for the Ag. Order
we would have a carbon to nitrogen ratio of 27,
we put that along with its corresponding nitrogen concentration into our sheet here.
Okay so next we need to just calculate the amount of nitrogen uptake by the cover crop.
So to do that we take our biomass which we've already estimated
and we multiply it by 0.98 and then we multiply that by the percent nitrogen
and we get 87 pounds of nitrogen per acre
were taken up by the shoots of that cover crop.
So that's the total nitrogen uptake.
We're going to take our nitrogen uptake, the total amount
and then remember from our calculated credit we get 97 percent of that
so multiply the 87 pounds per acre of uptake multiplied by 97 percent so there you
have it 85 pounds is a pretty nice credit.
I think in many cases farmers will get even more than that,
you know up close to 100 or more
but this just shows you for the standard credit you only got 30 pounds
for the calculated credit you can get close to three times more.
Anyway so there you have it so that's how you would calculate
the calculated cover crop nitrogen scavenging credit
for a Merced Rye cover crop.
Hopefully you find this helpful
I'll be happy to answer any questions that you might have about this.
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