NASA researcher says turf grass largest irrigated crop in the country - 3 times the acreage of

[JohnWxy]

irrigated corn.

http://www.faircompanies.com/main.aspx?uc=notampl&sec=1&id=400

NASA researcher Christina Milesi who has researched the size and impact of US lawns reports : "Even conservatively, I estimate there are three times more acres of lawns in the U.S. than irrigated corn."
~~
Milesi and her team discovered that the impact of lawns is big, especially with respect to water. To keep our nation's lawns watered requires 200 gallons per person per day of water, or double the daily indoor consumption for an average family of four.


I have to wonder how much fertilizer is consumed on lawns compared to agricultural uses.

[kirby]

1. That makes the assumption that everyone waters their lawn..

I know I dont or very rarely.

[JohnWxy]

5. I don't know if she assumed anything. They used satellite sensing data for their conclusions.

[kirby]

9. Well I read the article before replying and it did not mention that...

I was not aware they were using Satellite data. The article (and your summary) said

"Milesi and her team discovered that the impact of lawns is big, especially with respect to water. To keep our nation's lawns watered requires 200 gallons per person per day of water, or double the daily indoor consumption for an average family of four."

That sounded like one of those back of the napkin extrapolations you see in so many science articles.

Upon reading her research, I think appears they did extrapolate. They did not use actual satellite data from what I can tell. Where did you get your Satellite info from?

From the conclusion of the study:
http://www.isprs.org/commission8/workshop_urban/milesi.pdf

"In this study we mapped the total surface of turf grasses in the
continental U.S. and simulated its water use and C
sequestration potential under different management practices
for irrigation, fertilization and fate of the clippings. Rather
than trying to accurately quantify the existing fluxes, we
simulated scenarios in which the entire surface was to be
managed like a well-maintained lawn, a thick green carpet of
turf grasses, watered, fertilized and kept regularly mown. The
accuracy of the results is therefore limited by both the
uncertainty in the mapping of the total lawn area and by the
simplifying assumptions made while modeling turf grasses
growth."

[JohnWxy]

17. Sorry, been off-line for a while. HEre is one link:

Here is where I got the notion they used satellite data:

http://www.earthsky.org/teachers/article/lawns-single-largest-irrigated

"JB: Since 2003, Milesi has used satellite data and high-resolution aerial photography to calculate how much of the U.S. is covered by lawns – from those in people’s yards to commercial lawns and golf courses. "



http://www.sciencedaily.com/videos/2006/0404-greener_grass_less_water.htm

http://www.ivanhoe.com/science/story/2006/04/124a.html

as usual I was pushed for time then otherwise I would have included the links.

Of course they were extrapolaating - the alternative would be to go around and measure every lawn in the entire United States. Given that information, to be of any value, has to be timely measuring every lawn in the U.S. would get you data but a few years later than you would like to have it.

thanks for the links to her study. I didn't have time the last time I was on to go further (and read the actual report of their results - (rather than an article).

Here are some more quotes from the link you provided (it's interesting):

Two watering management scenarios were simulated. In one type of watering
management we followed the common recommendation that
during the growing season turf grasses require about 2.54 cm
(1 inch) of water per week (Schultz, 1999). In the simulations,
in the case of rainfall, rain made up for part of this amount.
The alternative watering management scenario, rather than
providing a fixed weekly amount of water, modulated the
irrigation based on the potential evapotranspiration (PET) and
precipitation, in this case calculated according to Priestly and
Taylor (1972). In this case, irrigation was simulated to be
triggered when the PET minus precipitation, accumulated since
the last watering event, exceeded 60% of the added water.
Irrigation then replaced 20% of the PET, bringing the water
availability to nearly 80% of PET. The effect of the two
different water management practices on the C and water
balance was evaluated comparing scenarios in which N added
through fertilization was constant and irrigation was either
fixed at 2.54 cm of water/week or modulated according to PET.
The simulation sites were assumed to grow either C3 (cool
season) or C4 (warm season) turf grasses, or an equal mix of
the two in the transitional region, based on adaptation zones
(Beard 1973).

The growth of turf grasses at the 865 sites was simulated for
the following five different scenarios:

Control: turf grasses growth was simulated with no
management (no irrigation and no N fertilization) except for
cycling of the clippings;

Removed-146N: the grass was irrigated during the growing
season so that a total of 2.54 cm of water per week was
provided, fertilized with 146 kg N/ha/yr, and the clippings
were removed from the system after each mowing event;

Cycled-146N: same as Removed-146N, except for the
clippings, which were left on the site after each mowing event;

Cycled-73N: same as Cycled-146N, except for the amount of
fertilizer, which was halved to 73 kg N/ha/yr;

Cycled-73N-PET: same as Cycled-73N, except for the
irrigation management, which was calculated based on
Priestly-Taylor PET.

More details on the simulation methods can be found in Milesi
et al. (2005).

The simulation results were extrapolated to the continental
surface assuming that turf areas in the vicinity of a simulation
site displayed similar C and water fluxes. The continental U.S.
was divided into Thiessen polygons centered on the simulation
sites and the output results at each simulation site were then
multiplied by the total turf area estimated within the respective
polygon.

3.1 Estimation of turf grass area

The total turf grass area estimated in this analysis summed up
to 163,812 km2 (± 35,850 km2 for the upper and lower 95%
confidence interval bounds). This estimate, intended to include
all residential, commercial, and institutional lawns, parks, golf
courses and athletic fields, accounts for approximately 1.9% of
the total continental U.S. area, which compares with 3.5-4.9%
of the total surface estimated to be devoted to urban
development (Nowak et al., 2001; National Association of
Realtors, 2001). Our estimate is compatible with the results
from other studies, in particular when considering the recent
growth in population and urban areas in the U.S. (Fulton et al.,
2001). DPRA, Incorporated (1992), assuming turf surface to be
directly related to the population, estimated a total surface of
188,180 km2, among which 94,090 km2 of home lawns
(Grounds Maintenance, 1996). A 1987 study by Roberts and
Roberts (1987), estimated a total surface of 100,000-120,000
km2. Another study, focusing only on residential lawns,
analyzing state-based average lot sizes of single family homes,
estimated a total home lawn area ranging between 58,000 km2
and 71,680 km2, considerably downsizing DPRA’s estimate of
home lawns (Vinlove and Torla, 1995). One of the earliest
estimates of total turf surface dates back to the late 1960’s,
when it was reported that 67,000 km2 of lawn existed
nationally (Falk, 1976).

Even when the estimate of total surface is considered to be
closer to the lower bound of the 95% confidence interval
(127,962 km2), it appears that turf grasses would represent the
single largest irrigated “crop” in the U.S., occupying a total
area three times larger than the surface of irrigated corn
(43,000 km2 according to the 1997 Census of Agriculture, out
of 202,000 km2 of total irrigated cropland area)."
------------------------------------------------------------------------------------------------------------------------------------------------------------


As you can see they were not assuming daily watering but in fact considered a two different scenarios. I think it looks like they put considerable thought into coming up with a pretty good estimate of water usage and (in another section of their report) the amount of area for lawns. At any rate I think you will agree it wasn't a quick and dirty swag. This doesnt' surprise me as these are serious scientists working for NASA.

Of course they extrapolated, (this is more practical than going around measuring every lawn in the U.S.) Extrapolating is not making off the cuff assumptions - but rather using a well thought out basis for such extrapolation.

[lapfog_1]

7. The cool thing about remote sensing...

They can TELL if you have been watering or not.

And how much.

All has to do with the water vapor and thermal imaging of the crop/forest/lawn.

And correlate with rainfall records and you have a fair idea how much water has been used since the last pass of the satellite.

( I say this as the former NASA person in charge of storing this exact data for the Data Acquisition Office, part of the EOSDIS program... many Terabytes of data when I left in 2000).

[kirby]

10. Actually, googling some more, I dont think she did this...

Here is the study...

http://www.isprs.org/commission8/workshop_urban/milesi.pdf

It looks like it was a computer simulation...

Conclusion:

"In this study we mapped the total surface of turf grasses in the
continental U.S. and simulated its water use and C
sequestration potential under different management practices
for irrigation, fertilization and fate of the clippings. Rather
than trying to accurately quantify the existing fluxes, we
simulated scenarios in which the entire surface was to be
managed like a well-maintained lawn, a thick green carpet of
turf grasses, watered, fertilized and kept regularly mown. The
accuracy of the results is therefore limited by both the
uncertainty in the mapping of the total lawn area and by the
simplifying assumptions made while modeling turf grasses
growth."

[lapfog_1]

11. Well, they could have.

modeling is ofter easier. I suspect that they only used the summary products to determine the actual amount of lawn in suburban areas. That would be a natural product as part of the overall crop identification program.

Of course, they could have estimated that as well for their model.

The cool (but harder) thing to do would be to directly interpolate the actual data, rather than modeling it.

Then see how it matches with what various city water departments have as their data on water usage.

[XemaSab]

13. The other cool thing about remote sensing

is they can see pot farms under redwood canopies. :P

[lapfog_1]

15. Depending...

on a lot of things.

But they can see those camouflage nets the growers put up hoping to fool people.

:)

[90-percent]

2. Question

What percent of the area of the USA is paved?

I recall it was supposed to be 1% of the area of the USA is pavement!

Staggering, if true.

-90% Jimmy

[county worker]

3. If you fly across the country you can look down and see many sod farms.

They plant grass in circles so that the irrigation pipes can go in circles.

[JohnWxy]

6. I never even thought of that. I wonder is they included sod farms. I was just thinking of

residential yards. Good point.

[kristopher]

14. Irrigation for lots of crops is the same pattern.

Around here we have corn, soybeans etc and the irrigation dinosaur moves around the central feed.

[Richard D]

4. All that area . . .

. . . should be turned into food producing gardens, ideally organic and permacultured.

[drmeow]

8. I'm still trying to find a landscaper

to turn my lawn into xeriscape. I can't do it by myself. After that I will be very proud to have reduced my contribution to the amount of lawn space in the country (I'm keeping some lawn - for now).

[XemaSab]

12. If you were in California I could TOTALLY hook you up

but he only does California natives.

Have you tried www.highcountrygardens.com for plants? :shrug:

[drmeow]

16. I actually got estimates last year

but of the two I liked, one didn't respond to my e-mails until I called him and then was very dismissive (obviously had not real interest in the job even though they'd had to lay off the guy I had first started to work with), the other got fully booked. Now I've got other things I'm doing (solar panels on the roof, have to replace the garage door, and want to fix some outside stuff and paint the house before hand - who wants to paint after putting in new landscaping!). I've still got the name of the guy from last year and another name now. I just haven't found the time to get the other stuff fixed (and getting partner to pick a paint color is going to be a NIGHTMARE). SIGH - this has been on the house to do list for 6 years - since the day we closed. But it WILL get done. If I can get the house painted this year I can make the plans to get the landscaping done next year if this year doesn't work out.

But thanks for the offer :)

[ScottyMax]

18. Acreage and fertilizer

I think there was roughly 85 million acres planted to corn
last year. I have heard that the acreage for planted household
lawns is roughly 20 million acres and another 7 million for
parks, golf course, and commercial lots. In terms of irrigated
acres I would say that the vast majority of lawns are
irrigated while much of the corn planted is planted dry
(relying solely on rain for water resource). Areas of less
rainfall like nebraska use the most in terms of irrigated
acres. As far as fertilizers go I would think the corn would
use considerably more than lawns. Corn typically requires
about 200 lbs of N fertilizer to obtain competitive yields.
This number varies obviously with soil type, crop rotations,
ect. I can't remember the last time I fertilized my lawn and
it certainly wasn't at the rate of 200 lbs N per acre but
maybe the rest of the world does things differently. Unlike
irrigated corn all corn is fertilized with synthetics like UN
32 in very heavy amounts excluding a very small amount of
organic farms which still use fertilizer just organic. 

[AlecBGreen]

19. hi ScottyMax

welcome to DU! :hi: :toast: :party: