[jvanderbot]

This is pithy and needs a citation as much as other responses. agriculture use is massive.

https://www.visualcapitalist.com/america-land-use/

I used to work with precision ag and fish ecology depts at univ of Minnesota. In much of the Midwest, it is farm upon farm as far as the eye can see. Both these depts primary focus was on reduction or mitigation of nutrient runoff from farms.

But, in urban areas, it is absolutely correct that a good portion of the lakes have issues due to lawn runoff (summer) and salt runoff (winter). The local lake manager said that winter salt is the single most damaging contribution of people in our one instance. A lake in the next county over was devastated by phosphorous from lawn treatment. One next door was being savaged by carp.

Water is a precious resource and has multi vector threats. Where you live it may have a bunch of different problems, but for much of my state, and surrounding Midwest states where farms are widespread, farm runoff dominates simply because on a per acre sampling, farms dominate.

[ttyprintk]

All believable, but if we’re talking overall, NASA says satellite imagery shows the irrigated area for turf outweighing the next eight crops combined.

https://earthobservatory.nasa.gov/features/Lawn/lawn2.php

Looks like Visual Capitalist is just hosting maps from McHarg, https://mcharg.upenn.edu/

I don’t know if McHarg collects data that can be compared with NASA.

[njarboe]

> All believable, but if we’re talking overall, NASA says satellite imagery shows the irrigated area for turf outweighing the next eight crops combined.

If you have ever driven across the Midwest you know this is incorrect. I could not find that statement in the linked article but did find this:

“Even conservatively,” Milesi says, “I estimate there are three times more acres of lawns in the U.S. than irrigated corn.”

Irrigated. Most crops are not irrigated. From the article:

"This means lawns—including residential and commercial lawns, golf courses, etc --could be considered the single largest irrigated crop in America in terms of surface area, covering about 128,000 square kilometers in all."

128,000 square kilometers is about 32 million acres. A lot for sure. One acre for about 10 people in the US.

But the total cultivated cropland (not counting tree farms) is about 650 million acres. 20 times the lawn total. Corn alone is 93 million acres.

Total [1]https://www.fsa.usda.gov/news-room/efoia/electronic-reading-...

[ttyprintk]

Yeah for the purposes of runoff, we're prioritizing irrigated area over non-irrigated because of the potential for control. There are plenty of problems in areas where irrigation is not necessary; arsenic in Arkansas, Texas, Louisiana, etc.

I should have linked to the research rather than NASA, where author Milesi was interviewed:

https://www.isprs.org/proceedings/xxxvi/8-w27/milesi.pdf

>> All believable, but if we’re talking overall, NASA says satellite imagery shows the irrigated area for turf outweighing the next eight crops combined.

> If you have ever driven across the Midwest you know this is incorrect. I could not find that statement in the linked article

Link rot is kicking in.

https://web.archive.org/web/20160330015359/http://sciencelin...

[jvanderbot]

That's very interesting. It should be pointed out that all of NASAs data is open (by law - source I used to work there, subject to a short embargo for phds to be written). So anyone could have the same data underneath. But this analysis is cool.

So, the questions that remain:

1. Are lawns more or less likely to be treated with chemicals that harm waterways

2. Are lawns more or less likely to produce runoff of those treatments

3. Given answers to above is the net effect more or less than agriculture on our water.

I'm not seeing much that answers those questions specifically. It does appear there's regulations against phosphorous lawn fertilizer nowadays. But that's all I can find on a cursory search. I'm happy to believe they both are equally important nowadays.

[ttyprintk]

Those would be valuable to know, but I bet separating the non-point-sources is unachievable. I mean, we may be detecting latent (> 1 year old) hydrological concentrations from the combination of lawn, ag, failing septic tanks, and point sources that conveniently become non-point.

On that last source: the design is to concentrate liquid manure, which as a point source is a liability, and spray it over an area. I believe this makes it a non-point-source for the purposes of carveouts in the clean water act.