Evaluating your Irrigation System with the Mobile Irrigation Lab (video + Q&A)

For growers who do not have access to a mobile irrigation lab or a professional irrigation system evaluation, what first steps can they take to evaluate their system?

Kevin: Farmers can do an evaluation on their own, and it doesn’t have to be as involved as what’s shown in the video. Knowing what the pressure is at the pump is a key place to start, and understanding the pressure there and what you’re putting into the system. From there, understanding the pressure at some of the inlets is important; so for example, knowing the pressure at the very first inlet at the first submain. By knowing the pressure at the inlet versus the pressure at the pump you can determine if the system is losing pressure. This is especially important to compare at the pump and the first lines, and all the way to the ends of the lines. A simple way to do this is by having two pressure gauges at the pump: one before the filter, and one after the filter. These two gauges will tell you how much pressure you’re losing at the filter, and the second gauge after the filter tells you how much pressure is going into the system. As mentioned in the video, a pressure gauge, a pitot tube, and a poker are great tools to have on hand and you can stop a few places, poke a hole in the line and check the pressure. If there is a big pressure differential in the system, consider calling someone to inspect the system or do some more in depth checks to determine what’s causing the pressure loss.

Any tips on measuring irrigation water pH and conductivity and then checking soil pH and conductivity at various shallow depths – and any thoughts on correlations between soil and irrigation water pH and conductivity?

Davin: Knowing your water pH is really important, which is connected to water penetration. Basically, you can take water and soil samples. Soil samples can be taken pre-season and sent to a lab. The important thing is to sample soil that’s receiving irrigation water and is somewhere in the root zone. For water samples, you should test both groundwater and surface water if you have both sources. It’s good to test at the beginning of the season, especially with groundwater, and test when the water table is high, and also at the end of the summer when the water table has been drawn down. There will often be different chemistry at that point as things get more concentrated. These are important to see if you’re getting good water penetration and if you need to do any amending. 

Do you need any equipment from the grower when you come to our orchards? Would the loan of an ATV help?

Kevin: The Mobile Irrigation Lab is pretty self contained; I have the tools I need and my truck is small enough to typically fit down the orchard rows or I can walk. It can be helpful to have a gator if the acreage is significant but usually I’ll drive around the perimeter. The only thing I really need is an irrigation design plan on hand, which is helpful if the grower can’t come out and meet me in the field. This also allows me to give the grower more information in the report based on what I measure in the field. 

I’m trying to wrap my head around the extent or parameters or what types of drip irrigation / drip systems there are… is there a resource with a comprehensive list of all types of irrigation?

Kevin: Basically when it comes to micro systems, there’s micro sprinklers or micro drip. Typically in agriculture, there’s agriculturally produced micro sprinklers or drip, and there’s also urban or landscape irrigation. You can go to any manufacturer like Toro or Rainbird and they have lists of their micro sprinklers or micro emitters. Or you could visit an ag irrigation store in your area and see what’s available. Where I’ve traveled in different areas of California, people use different forms of the same thing. If you’re using a drip emitter, there’s a couple different manufacturers that make them, so it’s just about choosing which one you want based on different specifications like how much pressure will be run through it. Is it going to be really low pressure or do you need more pressure? There’s a lot of variety out there and a number of manufacturers, but it really comes down to micro sprinklers and drip emitters.

Davin: If you’re looking for the best system design, starting at the ag irrigation supplier and designer is a good resource. They’ll run through the design options with you. UC Cooperative Extension also has a lot of information on the different system types.

Do you use automatic flush valves at the ends of your lateral lines?

Davin: No, they’re all hand valves.

Do you do any treatments at the pump to maintain your lines (acidification, for example)?

Davin: In order to maintain clean lines, we’ve added chlorine to the system and left it in the lines. We haven’t had to do any acidification to break up buildup in the filters, but we do wash the filters frequently.

Kevin: It depends on your geography and what’s in your water, like if you have calcium issues or if there’s potential for bacteria from surface water. If it’s a bacteria issue, you’ll want to treat it with chlorine. Typically calcium is treated with acid injections. This is another good reason to test your water; there are labs all over the state and you can send your water in for testing. If you have a drip or micro system, it’s pretty apparent and you can see white residue around the emitters and can assume it’s a calcium issue. Flushing the lines, opening them up and looking at them is important, especially at the farthest reaches of the submains. If you see globs of bacteria, you’ll probably need chlorine. University of Cooperative Extension has done a lot of research on different types of chemical injections based on what’s in your water and what issue you may be having.

How do you get rid of silt from the small drip lines and how often do we need to clear these?

Kevin: Typically when the system is designed, the person designing or installing the system will take the water source into consideration. Starting with the right filter is really important – understanding the quality of the water and the issues that might be in that water and having the right filter for that system is important. Once the system is already installed, the best thing to do is open up the ends of the lines and flush them. I used to recommend that growers go through the system several times a year, but if you have several hundred acres and lots of submains, that’s a lot of manual labor. To do a basic check, the best place to go is the very end of the submain (at the very last line), where all of the debris accumulates in larger quantities. Moving up to the second, or third, or fourth line you’ll see a big difference with less and less debris as you move along to each line. So, focusing on checking the ends of the lines and keeping those clean is key because that’s really where the debris tends to end up.

How often would you recommend that a system check is done?

Kevin: I would recommend that folks check their systems regularly, especially with changing environmental conditions, like if you’re pumping groundwater where pressures can change quite a bit from aquifer levels dropping lower or higher, or drawdown effect from neighboring pumps. Paying attention to the pressure at the pump each time you irrigate and having a flow meter is really important because those will tell you – for instance if last time you irrigated it was 35 PSI and now it’s 30 PSI, you’ll be able to see that you’re not putting as much water on based on certain conditions. Doing a visual sprinkler check is another way to do this. Some people will even check every time the pump gets turned on.

Davin: We don’t turn the pump on without checking the system. We flush the filter and the submains on every startup. Sometimes we even check the sprinkler twice; even then, you’ll have problems that occur. You just have to do whatever your capacity allows. All our systems are micro emitters or micro rotators, so we can visually see pressure differences once you’re accustomed to looking at how a system like this is supposed to accomplish. This is different from drip tape where you’d need to wait to see a wet spot to see if it wasn’t working correctly.