Making it Rain: Irrigation at Harmony Valley Farm

By Gwen Anderson

“Water is the driving force of all nature.”  --Leonardo Da Vinci

This year's irrigation crew: Vicente (left) and Manuel M. (right)

Ever since there have been farms, farmers have been finding ways to get the life-giving force of water to their crops.  The blessing of a nice, gentle rain at just the right time is a great boon, but you can’t be guaranteed anything of that sort in farming, despite your skill and grace at rain dancing.  As farmers, it is our job to care for our crops, to give them what they need at the time they are needing it, and that includes water.  To learn more about how we water our crops, I spent some time talking to Farmer Richard and the leader of the irrigation crew, Vicente.

Here at Harmony Valley Farm, we have two main ways to deliver water from its source to our crop fields: subsurface and overhead.  Subsurface, or drip, as we call it, is when a small hose is buried in the ground under the crop.  This hose, called drip tape or drip line, has tiny holes in it that allows water to be fed directly to the roots of our crops.  The other method, overhead irrigation, is something most people are familiar with: sprinklers.  We have two methods of using sprinklers, either many small ones connected in a line or one very large one we call “the gun,” which slowly pulls itself across the field with water pressure.

Drip line in our squash field.
Richard dug it up a little bit so we could see it in action.

Both types of irrigation have their advantages and disadvantages.  Vicente prefers the drip tape because it is a onetime set up and stays with the crop for the whole season.  When it comes time to water the crops, you just hook up the pump, check for leaks, and let it run.  The main disadvantage to this type of irrigation is that it is not reusable.  Every year, we need to purchase new drip line to replace what we used the year before.  Every spring, we bury the drip lines in the fields where we will plant the crops we use it for, and we have to pull it up at the end of harvest.  If you watched the garlic field tour video we posted to Facebook a few weeks back you saw some of our harvest crew removing the drip tape from the soil as the lifter brought the garlic out of the ground.  Due to the onetime use nature of drip tape, the price to use it to irrigate crops that are planted and harvested once, like radishes and cilantro, would be high.  Instead, we save the drip tape for long season crops, like onions, garlic, peppers, tomatoes, and potatoes.

This years onion crop, with cover crops planted to reduce
weeding needs and sequester carbon.

There is also the problem of leaks in the drip line.  If the line isn’t buried deep enough, or if a tractor gets off course even a fraction of an inch, the drip line can get ripped by our cultivating equipment.  While the pump is running, Vicente checks the fields to make sure water is running through the whole drip line.  If there is a spot in the field that isn’t getting water, it takes a little bit of detective work to find where the water stops, sometimes just by digging up portions of the line.  Vicente says it is easier to find the leaks in beds that have plastic mulch on them.  This is because the drip line isn't buried as deep as on a regular bed since we don’t have to use the cultivation equipment on beds with plastic mulch.  When the leaks are found, he cuts the ripped section of the tape out and replaces it with a hard plastic coupler to reconnect the two pieces of the spliced tape before burying the drip line again.  In recent years, we’ve been trying different techniques to alleviate the problem of ripping the drip tape with the cultivators.  Burying the drip tape deeper is one of those measures.  Another trial technique this year has been planting cover crops in the wheel tracks of some of our fields with drip tape in them.  Not only does it mean we don’t have to run the cultivators through those fields as often, but it has the added benefit of more green, living plants sequestering carbon out of the atmosphere.  That is a win all around!

Drip line is buried when the plastic mulch is laid.

The drip tape does allow us to do something we can’t do with sprinklers and the rain gun.  We can fertigate!  Fertigation is when we use the irrigation lines to “spoon feed beneficial nutrients right to the roots of the plant,” as Farmer Richard says.  Unlike other methods of applying fertilizer, with fertigation we aren’t applying it to everything that has access to the top soil, like weeds.  We can also use this method of applying fertilizer when the crops do not need to be watered.  We hook the fertilizer up to the pump, run it through the field with minimal water to facilitate the delivery, and turn the water off when the fertilizer has been administered.  No need to run the pump for 7 or more hours like Vicente would if the field was needing water.

What do we use to fertilize our fields?  I could write a whole article on fertilizer alone, so I’m just going to stick to a few highlights.  Any of the fertilizer we use with fertigation needs to be water soluble, or able to be dissolved in water.  There are two ways to do this: either have the fertilizer already be liquid, or use a water soluble solution.  The main fertilizers we use for fertigation are either liquid fish and seaweed, or a fish powder.  When the crops are starting to put on fruit, we give them extra potassium, the mineral plants use to produce fruit.  We also provide our crops with a vast assortment of beneficial microbials and other micro nutrients that do everything from promote total plant health to deter pests.  

Sprinklers running to sprout radish and cilantro seeds.

Overhead irrigation, or our sprinklers and “rain gun”, is mainly used to germinate seeds and when the crops are small.  This is the type of irrigation we use on our weekly planted crops, like radishes, and crops with small seeds, like carrots.  To use the sprinklers, Vicente and the irrigation crew lay out aluminum pipe in the field that needs to be watered.  These pipes are connected to a pump that has been placed in a water source near the field, either the Bad Axe River, a creek, or the well at our Hammel property.  Once the field has been watered for the appropriate amount of time, the pipes and pump are picked up and either stored or moved to another field to start the process over again.

The rain gun works in much the same way, except the pipes are not laid through the whole field.  Instead, the rain gun follows a thick, sturdy hose that needs to be laid out in the field we want watered.  Vicente uses a tractor to slowly pull the hose through the field, with one of his irrigation crew members ready to radio him when the hose is to the end so it doesn’t break.  Once the hose is laid and the gun is ready to use, the pump is turned on and the gun sprays water over the field, slowly following the hose back to the pump.  As the gun “walks” through the field, it coils the hose back up on a reel so it is nice and tidy for the next time Vicente and his team need to use it.  This particular method of irrigation is only used when the fields are very dry.  Luckily, we haven’t had to use the rain gun this year.

"Rain gun" being used in our kohlrabi field in 2017.

The advantages of overhead irrigation are reusability and portability.  The aluminum pipes are long lasting, thus we can use them season after season.  Since the pipes are also portable, we don’t need to worry about damage from our cultivation equipment.  However, that portability comes with its own challenges as well.  I mentioned earlier that Vicente runs the water pumps for at least 7 hours, and may need to run it for as much as 12 hours if the crop is very dry.  That can make for a long day if the pipes aren’t out first thing in the morning.  As leader of the irrigation team, it is Vicente’s responsibility to turn off the pumps at the appropriate time and to check on them during the watering process.  It is a responsibility he takes seriously.  “Sometimes, when I’m finished for the day, and I’m tired and want to go to bed, I can’t go to bed because I have a pump out there that I need to turn off.  I have to wait until the gun gets to the reel and shut off the pump so things don’t get over watered.”

Over watering isn’t the only reason to stay up and check your pumps, either.  If the pump needs a tractor to run it, you need to make sure it doesn’t develop a mechanical problem, or you risk damaging the tractor.  Also, if a hose comes loose and you don’t have an automatic shut off switch installed, you could be pumping water directly into the ground near the pump instead of through your field.  “I’ve never done it,” Farmer Richard told me, “but I’ve heard stories of if you didn’t get up in the middle of the night and catch it, the next morning you’d have a hole deep enough to fit two school buses in.”

Beautiful peppers from 2012, the fruit of the irrigation
crew's dedication and effort.

During a drought year, like the one we had in 2012, that lack of sleep can really add up.  “You start doing that for about 6 days in a row and it gets old,” Farmer Richard told me.  Vicente and his crew were working around the clock for two months to keep our crops watered and healthy.  “That was terrible,” Vicente admitted, but he was dedicated to ensuring the crops were getting taken care of.  Farmer Andrea recalled one night that year the irrigation team was having trouble getting a water pump started, and Vicente was exhausted.  She had told him to go home, but Vicente said “I can’t go home, I need to get the water going.”  After some reassurance, Vicente took her advice.  “It was a very hard year,” Farmer Andrea stated.  “He was up early shutting off pumps and switching things over, because he had to in order to stay on top of the water needs.”

However, the crops were beautiful.  Farmer Richard admitted to liking drought.  “These excess rains just promote disease like nobody’s business.”  Even Vicente said “we should have another year like that.”  In the end, the beautiful crops are what make all the work worth the effort.  It doesn’t have to be a drought year for the effects of ones efforts to be seen, either.  “When the crop is good, and I know it is producing nice,” Vicente told me, “that is what makes me feel good.”

An irrigation pump (right) connected to a water filter (left)
running water to the drip line in our squash field.

While both types of irrigation have different uses, they do share some of the same challenges.  With either type of irrigation, we use water pumps to get the water to where it needs to be.  Vicente is in charge of all of the equipment, and needs to ensure it is safely put away when not in use.  We do our best to keep an eye on the weather, but sometimes rain catches us off guard.  If it rains a lot and we have left a pump at a site near the river, we just might loose the pump to the water.

Administratively, we need permits from the Department of Natural Resources to pump the water to our fields.  The DNR assesses whether our water usage is going to have a negative impact on other people who also use the waterways in question.  There are strict guidelines the DNR uses to ensure this, and if we are awarded the permit, we are only allowed to pump the amount of water allocated on our permit.  Due to this, we have to report our water usage at the end of the year.  We lease land and use several different water ways, so we have several different permits.  The water usage reports are filed separately for each permit.  Vicente keeps records of where he pumps water, what kind of irrigation he uses, and how long he runs it.  He then calculates the water usage and turns it in to me at the end of the year.  It is my responsibility to enter the information into our records and file the reports with the DNR.

Vicente checking the sensor in the squash field.
No need to turn the water on here!

We’ve gone over the different methods we use to irrigate our crops and some of the challenges inherent to doing so, but how do we know when to do it?  Vicente uses a device called a tensiometer to measure the amount of water that is saturating the soil.  The sensor is buried in the ground at root depth, which for most of our crops is 6 inches, and then marked with a flag so Vicente can find it later when he needs to take a measurement.  He uses a portable sensor reader that he hooks up to the sensor that will display the kPa (kilopascals) reading.  Our tensiometer is set up to read 0 to 200 kPa.  0 kPa means the soil is as full of water as it can be.  Depending on the type of plant, the kPa reading they like to be at is different, so Vicente has a chart with the tensiometer to help him out.  Onions “drink a lot of water,” as Vicente says, so he waters them when the sensor reads 25.  If the sensor reads more than 25, it means he needs to get to work immediately and give the onions a drink.  Celeriac is another crop with a desired kPa level of 25.  Sweet potatoes, on the other hand, are a tropical crop and require a lot less water, 200 kPa according to Vicente’s chart.  Most of our crops land in the 45 kPa range.

Due to the nature of the sensors, we keep them where they are “planted” for the season. We do our best to have a sensor in every field, especially in fields where we have drip lines.  While the tensiometer is an invaluable tool used for irrigation, we sometimes have to just water the plants when they look thirsty.  Vicente keeps a close eye on the crops that don’t have sensors in them, and when they start showing signs that they are in need of a drink, he and his crew set up the irrigation systems.  Richard says that generally, our crops need about an inch of water per week.  “Are they going to die if 8 days go by and they haven’t had an inch [of water]?  No, but they might stop growing.”

2018 Sweet Potato Crop, which Vicente stated he was very
proud of due to the excellent production we had.

Luckily, here in Wisconsin, there isn’t a great need for irrigation like in some of the other arid states.  Mostly, we use irrigation to promote consistent growth in our crops and to germinate seeds.  “We don’t want to baby our crops too much,” Richard stated.  “If you continuously water one or more times a week they tend to have shallow roots, so when it does get dry they are not prepared for it.”  In the end, you see the literal fruits of the irrigation team’s labor in your CSA boxes every week.  Vicente and everyone here on the farm work hard to make sure you get the best tasting, nutritionally dense produce we can offer.  It is a job everyone is proud of.  I think Richard summed it up best when he told me “there is some nervousness around irrigation, but when it works, it is wonderful.  Our crops just grow like crazy.”