MSU Extension Irrigation

So, today, we're here talking about the water supply options for specialty crop irrigation. My name's Lyndon Kelley. I work for Michigan State University of Purdue Extension. And listed on the title slide here is my phone number and websites of both the Purdue ag engineering irrigation page and the MSU Extension irrigation page. So when we're deciding on a source of water for irrigation for specialty crops, a lot of it depends on how much total water we need. Some sources can provide far more than others. Trickle irrigation, we often look at the total number of row feet that we're gonna be irrigating, and then divide it into the number of hours that we're planning to irrigate. That gives us a number that tells us how many gallons we would need. Often we wanna about double that number just because of expansion and, in the season, it becomes more complicated as we have multiple crops, to keep the irrigation going. In field scale, we tend to think about five gallons per minute per acre that we'd like to irrigate. When we do overhead irrigation, that number allows us to apply one inch of water every four days or 1/4 of an inch a day equivalent, which meets our sort of peak need for most summer weather. So a lot of the specialty crops use trickle and drip irrigation to maximize the benefit from applying the water just where the root systems of the plants that we're growing our crop, and avoiding watering areas between the crops. Here's an example of trees. This can be Christmas trees or a high-density fruit orchard, but each tree takes up about six 1/2 feet of area. If you think about a six 1/2 foot square, that's roughly 1/1000 of an acre, so each tree needs 27 gallons of water to be equivalent to a one inch rainfall on that area. And it's so we could actually count the number of trees and look at the amount of pumping time that it takes to provide that number of gallons. Surface water sources are often the first thing people come to as far as the potential source of water. Unfortunately, in a lot of situations, there's some downsides to these. Most of our surface water has some aquatic weeds and algae growth that becomes a potential clogging of the system or clogging of the distribution system emitters for drip and trickle or sprayers for overhead irrigation. Surface systems often use centrifugal pumps, which require a vacuum between the pump and the surface water, the top of the surface water. That means two things. A vacuum pump is required and we tend to need to have that centrifugal pump within eight feet of the surface of the water to be able to maintain that vacuum. The loss of that vacuum can happen if we're pulling water in too quickly or if our intake is too close to the surface. A lot of times we don't have that intake right in the middle of the flow, but at least three foot below the upper surface of the water. But we tend to form a vortex as water flows into those intakes. And, as soon as we suck air, we lose our vacuum and stop pulling in. Because of that, many surface centrifugal pumps are equipped with controls that, when we lose prime, we lose output. So they use a pressure indicator to shut the system down when we do lose prime. Surface water examples can be lakes, rivers, streams, ditches and ponds. All of these in both Michigan and Indiana are riparian sources of water, so they can used to the degree that you're not negatively impacting the neighbors. So the big advantage in surface water is that it's economical as far as the total pump-out pump cost. In some cases, an existing pond may be available, and that pond may have value to the farm other than just the water source. So it's popular to think about surface water. But often that pond is not centrally located from the system so that it's not in the middle of the cropland. It usually tends to be to the side. If it's a river, lake or stream, it's almost always on the side. Private ponds would be the one that has a chance of being centered, or drainage ditches. If you think about streams, creeks and drainage ditches, remember that municipal treatment plants upstream may be sources of contamination that you would have to deal with for human consumption crops. Also, beware of plant diseases that may be brought about by decaying material upstream from you. The bacterial stalk rot of corn is a common issue. And phytophra root rot is a major issue for vegetable production and fruit production from stagnant water bodies. Lake treatment for algae, commonly, they use 2,4-D or dicamba-based chemicals for eurasian milfoil control. And that has a potential risk for irrigation users downstream, so you'd need to be aware of that. The one place we see ponds really shine is where we have a high iron content in groundwater. In some areas of Michigan and Indiana on our west sides, we actually pump groundwater into ponds and let the iron precipitate out before we put it through drip and trickle systems. Ponds have some special challenges. When we're talking about creeks or rivers or drainage ditches, the water flows to you, but a pond is that reservoir, and it needs to recharge from the bottom. So, actually, when we look at a pond, what we have is a very big well or opening to groundwater. When we start pumping, that groundwater level will be equal to that in the soil adjacent to the pond. And as we pull it down, the level in the pond, then water will seep in the edges and hopefully recharge the pond. The actual size of the pond is not near as important as the recharge capacity. Because of this, when you first put in ponds, make sure to do some testing. The best time of the year to dig ponds is in late August when things are at their driest. And before you dig the whole pond, look at the best potential area and excavate down to your depth to see if the hole will fill and how quickly it will fill. Local excavators that have dug ponds before and have had success are gonna be your best choice of people to do this work, and your best source of information on what the potential is. They will often start in the best location and then follow the water as it enters the hole to make the pond have as much recharge as possible. When we think about using this water, the other issue that we have when we're using surface water is, if we go into drip and trickle systems, we're gonna need some type of screen or filter system. In most situations, a simple screen can work for overhead irrigation to pull out debris that would accumulate in the system. But in the case of drip and trickle, well water needs to have at least a disc filter. In line and surface water, we probably need something that has a automatic cleaning feature to it. So the picture here at the lower portion of the screen here is a large fruit tree orchard using a double bank of sand filters. Those sand filters require a double bank so that they can clean themselves. And you're operating on just one side of the filter at any point, and they have automatic cleaning. Often when we get into sand filters for trickle irrigation, the cost of the filtration system is greater than putting in the well that may not require the sand filter. It all depends on your specific location and the water in your area. Some of you are gonna have food consumption crops that we need to be aware of the Good Agricultural Practices or the GAP requirements. So you need to read through those GAP requirements before we choose our source of water. A lotta times we get into crops that we want to use the water for cooling purposes or we wanna be able to irrigate directly to the fruit to keep summer hot temperatures from affecting quality. In these cases, the water needs to meet the requirements of the GAP requirement. It has to do with the testing procedure in many situations, and a well is needed at that point to be able to meet the requirement. So most of the people I work with that talk about water supplies for vegetable production will steer you very quickly towards a well for this concern that, in the end, you'll need the well to be able to meet the GAP requirements or the sales contract requirements. Groundwater sources end up being the potential of meeting the requirements for both cooling, cleaning and irrigation. And because of that, many systems are installed using groundwater. Capacities are tremendously different. We see wells being our most common source of water in Michigan. About 2/3 of the water for irrigation purposes in Michigan is now coming from wells. And we've had a steady conversion, eliminating the use of surface water in a lot of areas in preference to well water. Wells have the capacity to go into the 1,200 and 1,400 gallons per minute on 12 inch wells, if in very productive aquifers. And most of northwest Indiana and southwest Michigan has these glacial aquifers that can provide the water in those quantities, if needed. Glacial wells are wells driven or dug into the glacial sediment. They use typically a stainless steel screen to prevent the sand from coming into the water column, and the pump is actually at the bottom inside the screen pulling the water. Rock wells, on the other hand, which are required in some places in Michigan, are drilled down into the bedrock, and then uses the bedrock to clean the water. So we're actually pulling from fractures within the bedrock. These wells use a solid casing all the way down to the bedrock and then seal themselves to the bedrock, and is a more costly form of a groundwater well. But in many cases, it's the only thing available in mid-state, both in Indiana and Michigan. Shallow suction wells and horizontal wells sort of both fit in the same category. They're capable of producing up into that 500, 600 gallons per minute. Basically, sock wells are a nylon sock over the top of a drainage tile. And we basically suck water from that pipe traditionally with a centrifugal pump. But now, in many cases, we're using a small well connected to the horizontal well, allowing us to use a submersible pump, and has advantages of eliminating the suction line. Shallow suction wells at one time were very popular, but are basically four and five inch wells equally spaced from the centrifugal pump to keep the vacuum equal between them, and they actually suck water from the screen. In both the case of horizontal wells and suction wells, the centrifugal pump needs to be placed within about eight feet of the natural water level within that well when it's not pumping, to allow that vacuum to be formed. Water quality for these wells tends to be much better and much more suitable for use in trickle irrigation or overhead irrigation compared to pond wells, ponds that are installed. So a sock well may be an option in the same locations that a pond would be, but would have the advantage of eliminating the filtration system and improving water quality for the irrigation process. One of the things that we need to talk about is this idea of using a existing well that's also used for human consumption, a home well. In these cases, it's necessary to, in both Indiana and Michigan, to install a Reduce Pressure Zone valve to protect the home water supply. This Reduce Pressure Zone valve is the required valving that is placed between the home well and the outgoing lines to the irrigation or, in some cases, livestock watering. So if you're thinking about using a line coming from a municipality for irrigation purposes, make sure to take into account the cost and the maintenance of the Reduce Pressure Zone valve that's there. The other issue that we see when we see home wells being used, home wells are typically designed to not run 100% of the time, and they cycle pushing water against a pressure tank. When we use those for irrigation purposes, often we are using the start mechanism too often and have trouble maintaining the system. So before you overuse your home well and end up having to make major repairs to that, consider having a dedicated water source for the irrigation purposes. So, we talked about the Reduce Pressure Zone valves, we talked about backflow valves that are required, and then the chemigation valve in the lower center, all devices to protect the water supply from anything that may be mixed with the water as it's going out into the distribution system. For all purposes, once water has left the source, we don't want it going back. Even if there is no chemigation or fertigation used, we don't want the water that's went into the irrigation system or the trickle system to come back down into the well or back into the surface water source. In a few situations, producers have considered capturing water from hoop houses. This does not work tremendously well in greenhouses because, when our peak uses happens, we don't have a lotta rainfall. Thus, our collection is low right at the time we need that most amount of water. There's a number of pieces of equipment that are needed to actually make this work. The one place that you see some potential would be where we're using fall or early winter hoop houses to extend our season. The increase in rainfall in the fall gets us closer to meeting the water needs of the plants that are in the hoop house structure. Either way, we would need to have collection tanks. And the collection tank needs to be sunlight-resistant so that we don't allow the water to heat up and cause algae problems. We're gonna need a jet pump to lift the water to our dispersal system, filters to avoid plugging. There's a lotta things in rain water that are not something we wanna directly drink, so we need to also think about some type of system and filtration to keep our equipment going. And then often we need some kind of backup to be able to accumulate water when we don't have enough rainfall to be able to keep the system working. There's good information in the MidWest Plan Service bulletin on private water well systems. Also, from the North Central Region, there is a trickle irrigation bulletin. Both of these have very good information for people getting started with irrigation, and allows people to take, at their leisure, investigate the process. While we're talkin' about information available, the sprinkler irrigation system's MidWest Plan Service 30 is an excellent book covering both pumps, wells, piping systems, energy sources for irrigation, and then also the overhead distribution systems like side roles, hand moves, solid set systems, linear moves, big guns and center pivots. So we've listed the places where you could get the MidWest Plan Service book 30 to sorta supplement your reference material on irrigation. We're gonna talk a few minutes about distribution systems for those people that haven't selected one yet. Make sure before you start that you're not locking yourself into something or making an investment that you're going to regret. A lotta times, especially in dry years, we see a lotta used equipment come out that are what we call hand move big guns. These are stationary pieces of equipment. And if you supply them with enough water, they may be able to water 150 feet from the pipe. So that 300 foot circle may be a very attractive way to water, but when you start looking at how to keep that uniform and do it continuously, there's some pretty big challenges. They're very intensive, both from a labor standpoint and from an energy standpoint. Both Michigan and Indiana have a number of places and crops grown that we wanna try to prevent frosting. And we see a lot of interest in irrigation systems that can both water the crop and build ice layers to protect the crop from freeze damage. We need to make sure we have adequate amounts of water to keep that ice wet. Otherwise we may actually do more damage than good. And this becomes a much greater amount of water to apply at any one time than what the irrigation needs. A lot of the blueberry installations now have both overhead water for frost protection and trickle systems for irrigation purposes. These are set in place, so we often think of them as solid set, not moveable. What's more common to see in Michigan for vegetable production is hand move systems. But you'll see vegetable farms that will have almost semi-loads of aluminum pipe in the three to six inch diameter range, and in each section of pipe, either 30 or 40 foot long, will have a stand and a impact sprinkler. These are very flexible systems. They allow you to configure the irrigation needs for that year and for that crop, and then reutilize the equipment. But then it's very high in energy cost, high in labor, and relatively low in uniformity. So it tends to be a little bit of a water wasting system. The investment per acre tends to be fairly small if we're using used equipment. We don't see a whole lot of new equipment in this area used to create those solid set systems. Big gun travelers is the same idea of those stationary big guns except they're designed to be pulled across the field. Thus, instead of having a 300 foot circle out there, we can create a 10 acre rectangle. So, typically, it's gonna throw water 150 feet of effective area each side of the traveler lane. And then we're gonna use systems that can cover 1,320 feet. So the typical 80 acre field would have eight runs in it. And if each run takes 10 to 12 hours, we could actually put an inch of water on in about four days of continuous running. Extremely high in labor and high in energy requirement to do this. But big gun travelers have been a starting point for many people's experience in irrigation. They are commonly used in the Christmas tree industry and other industries where only a few years out of the crop rotation is there really a tremendous benefit to irrigation. And big gun travelers allow you to cover a lotta acres without a lot of permanent investment. There's two types of big gun travelers, soft hose systems, where the system actually collapses the hose, and typically 3 1/2, four, 4 1/2 inch systems available. These, the main line, it goes down the center of the field often a varied line with risers, stationed with the risers 300 feet apart. The hose is then bled, in the picture to the top of the diagram, and then a cable is strung for 1,320 feet and anchored to, in our case, a tractor, but an anchor at the south end or the far lower end of the field in our diagram. The cable is slowly wedged in, pulling the irrigation hose and the distribution big gun across the field to create that 10 acre parcel of irrigation. In the case of hard hose travelers, no cable is needed and there's 1,300 feet of hose used to create the pattern. The hose is actually used to wench the hard hose traveler across the field. Thus, the supply is always on one end of the field in that 1,320 acres. Center pivot irrigation dominates most of the irrigation in both Michigan and Indiana with about 3/4 of the acres being irrigated under center pivots. The trend towards center pivots comes from an efficiency in both labor, energy and water. All three of these are conserved to the greatest point when using center pivot irrigation, although it's still overhead irrigation. So, drip and trickle tends to shine, especially in plasticulture where we can control weeds at the same time. Center pivot irrigation really shines where we have large areas. If we think about a 160 acre field, if we draw the biggest circle in that 160 acre field, it would be a 1,320 foot. So we could have a seven span machine covering 1,320 foot making that circle. Then there's an end gun or a large gun on the very far end from the pivot point that's turned on to cover the corners, bringing our coverage area up into nearly 140 acres from that machine. And typically, when you fly over the arid Nebraska areas, these create the circles that we often associate with irrigation. The big thing to remember, that if we cut that machine in half and think about 660 feet inside of a 40 acre circle, even though the machine's cut in half, our acreage is cut to 1/4 of the potential that we had with the bigger size. Thus, it's much cheaper to use center pivot irrigation in the largest fields and pretty cost-prohibitive when we get down to small fields less than 40 acres to install center pivots. One way to try to reduce that cost would be to tow the pivot to multiple locations. The challenge is that that needs to be designed to be done in the peak of a season at least twice a week. And so we rarely see systems be very effective that have more than two center points and are towed back and forth. The one place that these really shine is where we have a crop rotation that really only has one crop that really benefits from the irrigation. By moving the pivot just annually, just once a year during the off-season, to the new location, you can always keep your irrigation investment on your high-dollar crop. And thus, we see a lot of towable center pivots that are just towed on an annual basis. We're gonna talk later about drip and trickle but I wanna make just a couple points. Drip and trickle really shines when we're lookin' at smaller plots, less than 40 acres, oh, man, clear down to garden size plots. And it really works well where we do not have total saturation of the soil with roots between the rows of the crop. So Christmas trees is one that we often think about in this situation. Plasticulture, that idea of actually covering and preventing weed growth, and helping the soil build some heat within that row really shines. The drip and trickle tape is placed underneath the plastic and ends up being able to weed control system, a watering system, and with the use of fertigation, putting fertilizer through the irrigation water feeding system. So here's a diagram. There's really not a lotta competition. It's just one system works better than the other. We think about corn, where we have total root saturation. In a very humid environment, we lose very little water to the air, and we have some benefits from actually washing or cooling the crop. So overhead irrigation works really well in corn and soybeans. But when we start looking at specialty crop, here are examples of Christmas trees, and we have a spacing that has a huge amount of non-rooted area between the rows. Doing overhead irrigation in these situations would we have tremendous amounts of waste. So, applying the water right to the row with a drip system becomes much more cost-effective.