Who grows crops in circles, as seen in this picture?
It’s because of the irrigation system used, which is called a center-pivot system. There is one pipe, which feeds a long boom pivoting around it. The relatively low cost of such a system outweighs the fact that you aren’t making efficient use of the field:
http://lindsaymanufacturing.com/zim_agsysystem_cntrpiv.asp
A variety of crops may be grown this way.
You also sometimes see irrigation systems that look for all the world like giant lawn sprinklers. They also have a circular pattern.
This is very common in the American Midwest, such as these aerial photos:
Colorado: http://terraserver-usa.com/image.aspx?t=1&s=14&x=112&y=1436&z=14&w=1
Kansas: http://terraserver-usa.com/image.aspx?T=0&S=16&R=17&C=14&W=1&ref=C&ClickAt=?19,24
Nebraska: http://terraserver-usa.com/image.aspx?t=1&s=15&x=106&y=728&z=13&w=1
You sillies!
It’s for CROP ROTATION!
;j
We have those crops in the UK too ( top picture)… . usually tomatoes. Apparently the seeds are practically indestructable.
Moderators, moderators!! This guy needs watching!
Way back when, in the bad old days before treatment plants for sewage were common,the sewers just dumped into the river. The river banks downstream from the outlet were lined with volunteer tomato plants.
They’re an attempt to make things easy for the aliens who joyride over to this planet to make crop circles…
Do the farmers plant outside of the boundaries of the irrigated area? And do they sow in a circle? Or do they sow in straight lines like Midwestern farmers?
IANAWF[sup]1[/sup], but it’s almost certainly impractical to drive a seed drill around in concentric circles, and there’s nothing to be gained by doing so. They plant straight parrallel rows like any other field. I would imagine that a farmer who knows they are going to irrigate a field this way may adjust the lengths of their passes when planting the field to avoid wasting too much seed on areas which aren’t going to get watered, but that’s a WAG.
As to what an individual farmer might do with the unused corners, who knows? Some of those aerial photos seem to show smaller rectangular fields or buildings located in the corners. IIWAWF, it would probably occur to me to use one of those corners as a place to put up a pole shed to house some equipment, or something like that.
It’s sort of an imprecise system anyway - if the sprinkler heads along the tube are all squirting out water at the same rate, the outer edges get less water per square foot than the inside of the circle because that part is traveling faster. This article mentions that they lose about 35% of the water due to wind and evaporation:
http://ga.water.usgs.gov/edu/irsprayhigh.html
[sup]1[/sup] - wheat farmer.
No need for a disclaimer that you’re not a farmer, as you’ve made that abundantly obvious in your other comments.
I’m not a farmer either, but I grew up on a farm and am still frequently out there. We don’t have any irrigation pivots, but several neighbours do.
-
Absolutely you drive in circles whenever possible, because the wheels on the pivot make deep ruts (no suprise, since they create their own mud) that are not fun to drive across at all. Now, I’m not sure if it’s typical to seed in concentric circles, since one could first run a cultivator in circles and work out the worst of the ruts, then drive your seeding equipment in straight lines - though note that some seeding equipment (i.e., discers) can’t be run in back and forth parallel lines, but needs to always be travelling the same direction as the last pass, which would dictate concentric circles, just as it dictates concentric squares in rectangular fields. Newer machines like air drills don’t have this issue. But you would run one circular round around the outside and then use that area for turning if you were doing parallel passes in any event (well, actually more likely the circular outside pass would be done last). Most guys around here have their pivots in hay most of the time, so they’re not seeding every year anyways, but I imagine this isn’t the case nearly everywhere.
-
Unwatered corners are used for whatever unirrigated land in the region typically is. If you’re in a near-desert where nothing grows sans irrigation, then it’d just be unused. Hereabouts it’s typically cereal grains, or unirrigated hay (just gives 1-2 cuts a year instead of 3, is all). Utility buildings are certainly a possibility as well.
-
It’s a very precise system. The nozzles put out differing amounts of water, depending on where they are. The inside nozzles put out enough less water to exactly compensate for the fact that they travel much slower. The only place this breaks down is at the end-gun, which is a huge-ass reciprocating sprinkler at the end of the pivot designed to extend the effective length of the pivot and to shoot water into the corners to a degree. These things are just giant versions of your typical lawn sprinkler of the variety that shoots bursts and slowly knocks itself in a circle, except that the bursts in question are big enough to soak a person right through instantly, not that the kids who were riding in the back of the pickup would know anything about that.
-
A lot of newer models (and, I believe, retrofitted older models) have sprinkler heads hanging far below the framework so that the water doesn’t have as far to fall in order to minimize evaporation losses. I don’t know what sorts of percentages they’re looking at, and of course those would vary dramatically depending on the weather. 35C, low humidity, and windy is going to evaporate a lot more water than 22C, high humidity, and calm.
Squash?
I don’t think that row crops, such as corn or soybeans, that are harvested by picking the fruit, seeds or whatever off individual plants are irrigated and planted in circles. These crops need to be cultivated as they grow to keep weeds down. Rows have spces for the cultivating machine wheels to run. This could change in the future for corn and for those farmers who simply chop the corn up for fodder.
This method of planting and irrigation is used for the seed grasses like oats, barley, wheat or the hays such as clover, alfalfa, timothy and the like that are broadcast seeded. These are harvested in bulk by cutting, drying in place and baling the hars and cutting and separating the seeds by combines for the seed grasses.