I’ve ever been flying in an airplane and looked out the window to see big green circles in the middle of a field, I wondered what it was. Today, I’m with my buddy Trey, a farmer, and I’m learning about center pivot irrigation systems. It’s a way to transfer groundwater to the field, using a circular pivot to apply it to the crops when they need it. To build the pivots, they first pour a pad for the pivot itself and then they dig ditches to run pipes to the pivot point. They also run wire alongside the pipe all the way to the pivot point to provide power. A father-son team then arrives to assemble the irrigation pivots. Trey has built 400 pivots in Alabama alone! to attach the sprinkler heads to the pipes and then attach the pipes to the trusses
Wow, can I help? No, no you don’t want me to help. No, stay out of the way so I’ve got to figure out how to establish myself as a trusted individual.
Give me, give me three on each side. Yeah, three uh law and three chord. Okay, got it. Three long, three shortest.
My first job, I think I’m in. They grew more tolerant of me and started letting me do more stuff. So, we laid out all the parts for what ended up being the first of three 200 foot sections of the pivot. After laying all that stuff out, we started putting together this pyramid that would eventually be the center of the pivot.
Faster, next we assembled an electronics box that would eventually run the whole pivot and we attached that to the side of that pyramid. Jose didn’t picked up the whole thing with a forklift and drove it over to the cement pad where he put it down and bolted it to the concrete.
Meanwhile, we jumped back over and started stringing together the large rods that would eventually support the whole pivot arm. These rods are in tension and I thought it was really cool the way we clasped them together with these little bracket mechanisms.
All right, teach me what my next job is. Andy yeah, he’s got a gasket on each one. See, he’s got a flat flat. Yeah, inside on the bottom is different. Okay, just make sure not to pinch it. Yeah, all the bolts on one side. Okay, that all the way down right. So, I’ve learned what happens is there’s like one task you learn and then you do it a hundred times. That seems to be the way this works.
When we finished organizing the pipes, the tension rods and the structural supports that holds it all together, we then unspooled electrical wire and attached it along the length of the pipe. We then started connecting these plastic tubes which I’m pretty sure is how we’re going to attach the sprinklers.
I was a little upset because these things are soft right and so they’re cross threading when you put them in the metal which is difficult but Jose was explaining to me that that’s on purpose because if there’s a storm and this whole irrigation system flips over or something these things will break off and you won’t damage the pipe so that’s on purpose.
Another thing that I’m observing here, this pipe has a little spigot in every hole. This pipe does not, it’s empty. It’s got one there, it’s empty. It’s got one there and so at this point I’m starting to understand.
I’m thinking as this Arc sweeps around the field, the the arm that’s closest to the pivot center this one’s not going to move as much as those out there so if you have the same flow rate in each location you’re going to water the inside of the field more than the outside of the field and that’s bad.
Oh no, we have hoses. What does this mean? And these are the sprinkler heads. Oh, they’ve got numbers. So, it feels like we’re going towards this. There appears to be a weight on the nozzle, the sprinkler head so that holds it down over the crop. I guess I guess I was wondering what those were. They’re weights.
At this point stuff started to get serious. Jose was on the forklift and he picked up one of the spans of the pivot which I learned they called Towers. We’d been hustling all day but there was a definite increase in the expected pace coming from the bosses.
How do you do it? I couldn’t get the bolts in because I didn’t know what parts of the truss were in tension and what parts were in compression. Jose of course understood everything. Man, that’s a man that’s done that a lot. So, we’re building trusses and I am the inexperienced man on the job. This feels stressful.
Boy, this is happening fast. The gloves are in the way. Coming in, coming in, just a whole pile of them. Once the tower started coming together, it was amazing to see how the pipe is an integrated part of the mechanics of the overall structure. So, it does two things, it provides the water and it also provides structure.
I’m jealous of the aprons, very jealous of the apron. At one point I made a mistake and complained about the 90 degree heat. Nice, this is not hot.
The next big step was to attach the sprinkler heads to the pipes and then attach the pipes to the trusses. the circle so they can get the same amount of water that’s right
Trey had that put in so we had two more Tower sections to build. By now, I had started to understand the process a little bit more and I even got to wear one of those little aprons which carries the nuts and bolts. I was really happy about that. We got the wheels up and running on the second one and then we took it over and attached it to the first. It was literally coming together. The third and final Tower section had a wrinkle to it which the first two sections didn’t have: it had a large spouty thing on the end. This was the outermost section at the end and it was essentially a large type sprinkler. I was starting to understand the engineering involved in this little contraption. It goes to one side and then cams over and reverses direction, and it’s all controlled by these little weights on the side.
The next day, I received the final blessing from my Jefe: he let me drive the forklift which, in my heart, was the best gift that Jose could have ever given me. After everything was in position, Trey just needed to finish connecting all the electrical lines and then run the well pipe up through the center of the pivot point. A few months later, I was able to come out and see how they actually performed in action.
I had two more big questions for me with this pivot. First, how do they distribute water evenly since the sprinklers at the end of the pivot would be covering a lot more ground while it makes a circle than the ones near the center of the pivot? I had noticed earlier that they spaced out the sprinklers closer together as they got further out and there were gaps up towards the center of the pivot. I learned that each nozzle had a regulator in it, a 10-pound regulator. The further you get from the center, the bigger the orifice is on the nozzle. This way, the plant needs to see the exact amount of water as that plant up there near the circle.
When I was at the pivot point, I could see the pipes get heavier as they filled up with water and it was spraying a lot wider than I anticipated. I was even allowed to run up the leg and see the phone set up. I heard the pivot moving and I saw the water coming out of it. It was a lot of flow and it was way more water than I thought.
I asked Jose if he liked his pivot and he said he did. It was more than I thought - there was a lot of engineering involved. It was really fun to see.