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Hello, everyone and welcome back. Today, I want to complete our discussion

Â on irrigation. If you recall, we left off talking about

Â irrigation systems and a little bit about soil water holding capacity, and some

Â methods to tell when to initiate irrigation.

Â And today, I want to continue on talking a little bit more about ways to determine

Â the amounts of water to apply. We want to focus a little bit on a couple

Â systems. One of them sort of takes off on the, the

Â use of the soil moisture indicator devices.

Â And then, the other one is the method that we call the water balance, or some call

Â the checkbook method. So recall, when we talked about

Â tensiometers. We said that they were, they were good

Â tools to give us an indication of the soil moisture, and we talked about how they

Â worked in having a tensiometer tool that's with a column of water that's continuous

Â with the moisture in the soil and in as the soil dries out, it draws on that

Â continuous column of moisture and registers a pull or a vacuum on the gauge

Â that we can measure. And we can relate that number to how dry

Â the soil is and if we have that system calibrated well enough, we can actually

Â tell when to initiate an irrigation. So, for example, I've given you some

Â numbers that might apply to sandy soils. Some numbers that we use here in Florida

Â for using tensiometers. So, for example, if the tensiometer on our

Â sandy soil at, say, 8 inches deep in the root zone for vegetables, when it reads

Â minus 8 to minus 15 centibars then that's sort of in that range, is where we want

Â the soil moisture to be. Now, notice I said minus 8 and that's

Â because this is a tension. And so technically, minus 8 is the correct

Â way to express the number. But by convention, most, most people that

Â use this system leave the leave the negative sign off and we just talk about 8

Â or 15 centibars. If the soil is a little heavier, for

Â example, a, a loamy soil, that irrigation or that ideal soil moisture regime might

Â be a little bit higher. So, if you have a tensiometer in the

Â ground and you're watching it over the course of the, the growing season and

Â you're watching the gauge then if the gauge approaches 8 or 6, the lower number

Â that indicates wetter soil. Remember the, the tension is what we're,

Â we're reading. And so as the tension increases and the

Â soil dries out and we approach a number of, say, 15 we would, for sure, want to be

Â initiating an irrigation event as that number, as that gauge approaches 15.

Â So, using a tensiometer to initiate an irrigation, or a TDR, or some other soil

Â moisture device often times takes a little bit of trial and error and hopefully you

Â have some research with these tools in your area so that you can then have some

Â numbers, some guidelines to go on. And so, it's important to have some local

Â recommendations as you consider using something like a tensiometer or a TDR in

Â your area for scheduling irrigation events.

Â Now, the reading with the, the tensiometer or the TDR or some other sort of moisture

Â indicator can give you a good indication of when to irrigate.

Â You still need to think about how long to run the irrigation system, how much water

Â to put on the crop because these soil moisture devices are, really seem part of

Â the picture and that's the soil, that's the soil moisture and we're not yet taking

Â a look at what amount of water the crop is actually using.

Â And so, what I would like to talk about now is to move over a little bit and, and

Â take a look at the other aspect the crop water use aspect.

Â Remember we've talked about ET or evapotranspiration and what that is.

Â Well, now, we are going to start using that knowledge in terms of figuring out

Â how much water to put on our crops. So, to do this, we're going to talk about

Â soil texture and we're going to talk about water holding capacity two things that

Â we've learned previously in the course. We're also going to be interested in the

Â rooting zone of our crop. Because that is the soil volume that we're

Â interested in knowing about the, the moisture content because remember

Â available water holding capacity in our soil.

Â And crops, different crops can have different rooting zones depending on the

Â depth of, of the roots in the crop. Some can be as far down as 4 feet deep, at

Â certain points during the, during the growing season.

Â We're also going to be with this system, we're also going to be measuring

Â evapotranspiration. We know what it is, but how do we measure

Â it? And we're going to learn about that.

Â Then, we're going to put all of this together, and we're going to visualize our

Â root zone and the water holding capacity in that root zone and we're going to think

Â of this in terms of a reservoir of water that the crop has to draw.

Â And knowing how much water the crop is using by our ET estimates, we can then

Â calculate and estimate how much water we need to apply to replace the water that

Â was taken out of our reservior by the ET. So how do we do this?

Â To get started we need to start at a point that the scientists, the biological

Â engineers call reference ET, and this is simply the water that's lost from a fairly

Â well level grass crop. Grasses are usually used as the, the

Â starting point. Sometimes alfala is mentioned in the

Â literature as a good reference crop. So, this is Reference ET.

Â This is the amount of water that's lost from a well-manicured, uniform grass

Â cover. So, here are some well, let me back up a

Â second. There are a couple of ways to estimate

Â this number. You can use some sophisticated equipment

Â to measure evap evaporation from that surface, that surrounding area.

Â But more likely, the biological engineers and the scientists that work with this

Â system had more depended on measuring certain parameters, certain climatic

Â factors and physical factors associated with that well turf well-manicured turf

Â area, and they feed that information into some models for example, the

Â Penman-Monteith equation. And they can calculate ET, reference ET.

Â And this is becoming more of an accepted way around the world to, to estimate a

Â reference ET. And this Penman-Monteith is a very common

Â way of, of doing it. Here are some numbers.

Â I just picked some numbers for Northern Florida around in this area the campus

Â area, and you can see they're expressed in inches of water lost, or ET per day.

Â And so, this is, if you can imagine, just visualize an inch-depth of water being

Â lost from that grassed surface, that would be an inch ET.

Â You can see though that we're talking about fractions of an inch.

Â And so, in January and February which in this part of the, you know, the world here

Â in Northern Florida is very cool. Short days relatively cool temperatures.

Â And then as the, the season progresses, the temperature gets warmer, the day gets

Â longer, the sunlight, the radiation, solar radiation gets more intense and the

Â evapotranspiration numbers increase. And that makes, you know, that's pretty

Â logical, as it warms up and you get more sun, longer days and so forth, the

Â evapotranspiration, the loss of water from the, from the grass should be more.

Â And as you go into the summer and, of course, here in this part of Florida in

Â the summer time is very, very hot and humid.

Â And so, you can see you can get up almost to 2 10th of an inch of water loss from,

Â from the grass surface. Notice also though, it's kind of

Â interesting that as you get into the later part of the summer, August and September,

Â you see the numbers actually go down. Well, August and September are some of our

Â hottest months. But also, the way the, the, the equation

Â works it factors in the climatic conditions of that time.

Â And that time during the year, we get a lot more cloud cover, the relative

Â humidity is higher, and those factors combined to actually reduce the

Â evapotranspiration. And that might seem fairly logical to us

Â also. And then later in the season, as the days

Â get shorter and the temperatures are cooler and less solar radiation, the

Â numbers go down and you can see, there's a very small amount of water lost from the

Â turf reference turf during that month. And so, you can convert these values to

Â gallons per acre per day, recalling that there's 27,150 gallons, plus or minus of

Â water in an acre inch of water. So, those numbers can give you the will

Â give you the, the information you need to convert the ET in inches to gallons per

Â acre, per day. So, for these ET, reference ET values, we

Â need to use values that are developed in your area.

Â For example, you would not want to use reference ET values developed very far

Â away, particularly if it's in a drier climate than yours.

Â Fortunately it's getting more and more common now to have these kinds of

Â reference ET numbers available through the Internet.

Â And so, some farmers have access to these ET values on a day-to-day basis.

Â If you do not have that available to you, there are published values, tables of

Â reference ET for various areas. And, at least they give you a rough idea.

Â You might have to use averages monthly averages or something like that if you do

Â not have access to real time data. For example, The University of Florida has

Â the, what we call FAWN, the Florida Automated Weather Network, and if you go

Â on this website you can see, on a day-to-day basis the ET values for several

Â actually several dozen weather stations scattered around the state.

Â So, so, it's very likely that a farmer would be in fairly close proximity to one

Â of these weather stations and be able to get fairly accurate and timely reference

Â ET values. So now, that's the ET, that's the

Â evapotranspiration of a well-manicured turf grass.

Â But we're not growing turf, we're growing other kinds of crops, cotton, corn,

Â peanuts vegetables for example. And so, how do we adjust that reference ET

Â value to a evapotranspiration value that's more close to our particular cropping or

Â production system in the field. And that's done by applying a, a

Â coefficient called K. And these coefficients adjust the

Â reference ET based on, mostly on the stage of, of crop growth and it's mostly re,

Â related to how well-developed the crop is and how much of the ground is covered by

Â that crop. These coefficient values would have to

Â come, you know, for your crops and, and for your production area.

Â I've given you an example of how a set of K, K values, or coefficient values might

Â look. I didn't identify any particular crop but

Â just realize that the coefficients are slightly lower early in the season and

Â then they grow with the, the development of the crop.

Â And for some crops that have a really, really high water use the numbers can

Â actually go slightly over 1 1.1, 1.2 at certain parts of the of the year, of the

Â growing cycle. So, depending on where we are in the, in

Â the growth cycle we would use the, the coefficient to adjust our reference ET.

Â So, let's look at an example for a sprinkler-irrigated crop, some crop on

Â sandy soil. Now, let's say that we looked up on the

Â Internet or on the website or we have access to some good reference ET data, and

Â we found that at this particular time during the growing season, the reference

Â ET was 0.15 inches. And we can do the calculation and see how

Â many gallons that is per acre per day that's lost from that crop.

Â And then, we also know that where the plants are growing, they're actively in

Â the active growing stage, and our coefficient, our published tabulated

Â coefficient for that time of the growing season might be 0.8.

Â So, we multiply those two together and get 3,200, 3,200 gallons per acre of crop

Â evapotranspiration. Now, we've converted it now to the crop

Â basis. Now, throw a little curve ball in here for

Â you. Remember, we talked about irrigation

Â systems, and the fact that they're not all a 100% efficient.

Â So, if we know how much water our crop is now using, and we want to replace that

Â amount of water, which is really the objective of irrigation remember, to

Â replace ET. But we know that our irrigation system is

Â not a 100%, then we need to adjust our crop water ET to account for that

Â relatively small efficiency. So, our 3,200 now becomes 4,270 gallons.

Â Because we may, we recognize that with a sprinkler irrigation system, we may lose

Â some of that water that we're pumping to evaporation in the air.

Â There might be some leaks. And so, if we know about the irrigation

Â system, then we can adjust. And, and even the book values of 75 may

Â get adjusted depending on your knowledge about your irrigation system even though

Â it says, sprinkler, if you're using drop nozzles, remember those are more efficient

Â than impact sprinklers on the center pivot.

Â So now, we know, we have another number we call our irrigation requirement.

Â It's a little bit greater than our actual crop water need, but we need to supply a

Â little extra to take, to take account for that small amount of water that's going to

Â be lost in the system. Now, sometimes the use of this approach

Â doesn't necessarily have to be done on a day-to-day basis.

Â You can, you know, you get into a week where the weather is fairly uniform.

Â You could do this on a, you could adjust the, the, the irrigation based on maybe a

Â two or three-day period. And so, I just wanted to make that point

Â that, you know, the weather is fairly uniform, you may use values ET, you know,

Â reference ET values, that might be the average of a two or three-day period or a

Â week a seven-day period. Now, we also have to realize that there is

Â the soil aspect to this. We now have calculated out how much water

Â we need to apply to that crop to replace that ET value for that crop.

Â But what if it rained yesterday, or last night, or the day before?

Â We need to, now, we've taken a look at the crop side of things, but now we need to

Â consider the soil and how much water is in the soil so that we can better gauge

Â whether or not to irrigate during a particular time.

Â So, let's just kind of step back and, and take a look at the soil.

Â Again, let's assume we're working with sandy soils.

Â And our sandy soil has a 0.75 inches of available water per foot of soil.

Â So remember, the last lecture we talked about available water holding capacity and

Â depletion values. So, we're going to, we're going to need to

Â recall that information. And let's also say that our root zone is 1

Â and a half feet deep. So, our crop is fairly well-developed, and

Â the roots are 1 and a half feet deep. So now, our root zone and the available

Â water that's in that root zone now, is 1.12.

Â And you just multiply 0.75 by 1.5, and you get 1.12.

Â So, that's how many inches of water we have available in that soil.

Â And again, we can convert that to a volume.

Â And let's further assume that we're going to, we're [laugh] we're little bit risk

Â averse. Okay.

Â So, recall back about allowable depletion. And so, 30%, we're going to allow, we're

Â going to allow our reservoir, our 1 and a half foot deep reservoir of water that's

Â available to the crop. We're going to allow that to deplete 30%

Â and at that point, we recognize we want to be irrigating.

Â Now, there is still water left in that reservoir, but on sandy soils, sometimes

Â farmers like to, to play it a little bit on the safe side and not let it go down

Â too much. Surely, 50, 50% might be acceptable but

Â recall, I painted 60% yellow on the allowable depletion.

Â And so, somewhere in there, depending on your you know, comfort zone as it will,

Â you're going to, you're going to determine some kind of a, a depletion.

Â And so, if we take 30% and we calculate that out then, now our reservoir that

Â we're managing is going to be about 9,000 gallons.

Â And on heavier soils, we might choose to have a little bigger reservoir and it

Â might be, you know, maybe 50% like 15,000 gallons.

Â So, this is the amount of water we're going to allow the crop to, to use and

Â withdraw and as soon as we see about 9,000 gallons disappear, we're going to

Â replenish that reservoir and add it back. So now, recall our irrigation requirement

Â is 4,270 gallons per acre per day. And we're going to, we're going to

Â irrigate when that's depleted. So, if you follow the calculations here,

Â if we do not get any rain it's going to take this crop at this level of ET about

Â two days to exhaust that allowable depletion, and it'll be time to initiate

Â another irrigation. The irrigation application rate of the, of

Â the system that you're using needs to be factored into this.

Â Now that we know how much water we need to put on we can determine how long to run

Â the system how long it takes for the pivot to go around, for using the lateral move,

Â hand-move system, you know, how long to allow it to stay in one position before,

Â before we move it. So, with this kind of information, we can

Â then determine the length of the irrigation event.

Â Now, just a few other points to make about this whole method here.

Â As the crop grows, the root zone is going to change, so early in the season, later,

Â later, and eventually it reaches sort of a, the full capacity.

Â So, that means our reservoir is going to change a bit during the season so we have

Â to account for that. Also, if we get a rainfall somewhere along

Â the line, we've got to add that in to our to our equations so that if that rain

Â added two days worth of ET, then, the that two-day period has now been satisfied

Â again and we start all over letting the crop use the, use the water down.

Â And so, rainfall has to be factored into this.

Â Also, this, this whole system relies on the fact that we're not farming in a in

Â field with a soil with a hard pan, or somewhere where there's a water table that

Â can contribute to the, the irrigation or the water needs of the crop.

Â So, if that, if that is the case then we've gotta factor in how much water is

Â being supplied to the crop from that from that water table.

Â And also note that the, the effect that increasing irrigation efficiency has on

Â this whole system. So, as farmers in, increase the efficiency

Â of their irrigation system by changing some of the technology and switching out

Â certain nozzle packages for example as the increase, as the efficiency increases then

Â that reduces the irrigation requirement. So, I hope you see how that math works

Â out. So, if you're in a situation where you can

Â make some changes, and for example, if you can get some incentive support to make

Â those changes, it's well-worth doing it because you'll save water.

Â And this is called the, the checkbook approach.

Â So, it adds in the irrigations and the rainfalls, and it subtracts out the amount

Â of water that, that the crop uses and you can add and subtract as you go along.

Â In fact there are websites out there and I've given you some references to some of

Â these on, on our course website that will help you get started with this particular

Â water balance or checkbook system to show you how, how to setup a spreadsheet and

Â how to keep track of it in, in real time. Now recall, we, we chose a, a fairly

Â comfortable 30% allowable depletion. Some growers I know, on sandy soils are

Â very reticent to go beyond that, in fact, you know, in other words, they like to

Â irrigate very frequently. So, some growers are inclined to keep our

Â reservoir filled and, and topped off with very frequent irrigation.

Â And I guess there are a couple reasons to caution against this general approach to

Â irrigation management. For one thing keeping the soil moist maybe

Â all the way up to the surface through that kind of an approach, encourages fairly

Â shallow root zones. And so, lodging to wind and things like,

Â problems like that might be enhanced with that kind of a irrigation strategy.

Â Also when you keep the reservoir filled or very, allow it only to deplete very

Â slightly, as the reservoir is filled, that means there is no, there is no free board

Â to, to, to hold rainfall. So, when a heavy rain comes, and your

Â reservoir is always is, is already filled, then the rainwater has to go somewhere and

Â it's going to push the water down. And much of the water that was in the

Â reservoir is going to be pushed below the root zone of the crop.

Â And if you have fertilizer, particularly mobile nutrients like nitrogen in the root

Â zone, in your reservoir, then those nutrients are going to be pushed below the

Â root system. So, those are two reasons for being a

Â little more careful about managing the water and leaving some free board in that

Â reservoir. So, for sprinkler irrigated for example,

Â for a pivot, from what we've talked about here, we need to know something about the

Â application rate of the system. For a pivot obviously, we can adjust the

Â travel speed to achieve the desired irrigation rate.

Â If you have heavier soils you're, you're going to be dealing with the potential for

Â a larger reservoir so you may be able to go more days in-between an irrigation

Â event, particularly if you choose a 50 or a 60% allowable depletion.

Â The rate of the irrigation is important. Remember, we talked about hydraulic

Â conductivity of soils, and so we want to make sure that our rate of application of

Â water is not going to exceed the hydraulic conductivity of the soil and end up with

Â flooding or, even worse yet runoff from the field.

Â And also, just another comment about the crop stages you know, some crops, like

Â some vegetable crops are very sensitive to even small or short timed drought stress.

Â And so, we need to be particularly careful during those stages of the production

Â cycle that we're, we're practicing good irrigation management and keeping enough

Â water available in the soil. Okay, here's another example.

Â This one is a little bit different. This is drip irrigation.

Â This one is different from center pivot or sprinkler irrigation because with drip

Â irrigation, we're just irrigating and managing a small volume of soil under the,

Â the plastic mulched beds, for example. I've given you a reference here that is

Â probably one of the, the only ones that I can find out there, it happens to be from

Â Florida dealing with drip irrigated crops and calculating amounts of irrigation

Â based on the water balance approach. So, let me just kind of take you through

Â this one as well by giving you sort of my rendition, my artist's rendition of a bed.

Â So, here's the soil, the brown, and this bed is going to be covered by a plastic

Â mulch. We are growing tomatoes we have drip

Â irrigation. Here is the drip tube.

Â Remember what drip irrigation is. This plastic tube then extends down the

Â row and wets a small area. In this particular case I've chosen an

Â area of soil under the, in the, in the bed of one, one foot by, by one foot.

Â It's actually going to spread out a little bit more in the bed than, than I, I was

Â able to show here in this picture, particular diagram.

Â So, let's assume we're growing tomatoes on 6 foot centers and, remember back to our

Â linear bed foot discussion, so here's another really practical application of

Â linear bed foot. And so, you should know now to take 43,560

Â square feet divided by 60 and you get 7,260 linear bed feet.

Â So, that's how many feet of drip irrigation we're going to have in this

Â field. And again, let's assume that we're working

Â on a sandy soil with 0.75 inch per foot water holding capacity.

Â 27:48

We're going to choose 50%, just to change the numbers here 50% allowable depletion.

Â And if you do the arithmetic you should be able to do the arithmetic, and come up to

Â 24 gallons per 100 linear bed feet of allowable depletion per hundred feet.

Â That then computes to 1,700 gallons per acre.

Â And the way that works is just visualize this, this long tubular area of wetted

Â soil under that bed. And so now, instead of thinking about a

Â uniform depth of available water, we're, we're dealing now with this long narrow,

Â thin area of wetted soil under that bed extending the full length of all of the

Â rows and all adding up to 7,260 linear bed feet.

Â And so, if you chop that up into 100 foot sections, the amount of available or water

Â in a 100 feet would be 24 gallons. So, our capacity, our reservoir is 24

Â gallons per 100 feet and that's 1,700 gallons per acre.

Â And so, I've given you a couple numbers there to help you with those calculations.

Â So, it'd be good to just go through and prove to yourself that you can come up

Â with the, the numbers. So now, let's just continue on.

Â Let's assume our crop ET was calculated to be 4,200 gallons, and our irrigation

Â efficiency with the drip irrigation is much higher than our sprinkler system, so

Â let's pick 90. So then, our irrigation requirement is

Â going to be 4,700 to account for a little bit of losses.

Â Now, with drip irrigation the losses are very minimal as far as evaporate,

Â evaporation because remember, these drip tubes are buried slightly in the soil and

Â they're under that plastic mulch so evaporation is going to be relatively

Â small but, you know, there could be some leaks.

Â So to account for that we'll choose a 90% efficiency.

Â So, we're going to get an irrigation requirement of 4,700.

Â Alright, now, there's, there's a curve ball coming here.

Â Because this is the amount of water that, that tomato crop is going to use during

Â the day and we need to, we need to replace that ET.

Â The problem is, we're dealing with a really small root zone.

Â Our, our reservoir is very small, compared to our previous example with sprinkler

Â irrigation. So, this amount of water cannot be applied

Â in one irrigation event, or it will exceed our reservoir.

Â And if we did that, then we're going to have a lot of depercolation and, and

Â potential leaching of nutrients. So, what do we do?

Â So, we can calculate up, we can use those numbers, and we can calculate out that we

Â would require 2.8 irrigations, we could use 2.8 irrigations during the day.

Â In other words, we split up the amount of water that the crop needs during the day

Â into several irrigations during the day. I rounded it up to an even three

Â irrigations, and then divided 4,700 by 3 and get almost 1,600 gallons per acre in,

Â in an irrigation event. So, see the problem that we have now when

Â we have a small reduced reservoir that we will with drip irrigation.

Â Now, that, that, that has an advantage because we're irrigating only the root

Â zone under the plastic mulch, we're not irrigating out in the inter-row area out

Â here as we would if we were using sprinkler irrigation.

Â This is where weeds could grow, we could have, remember our picture of the, the

Â rainstorm and the movement of water off a, a mulched field in the alleys.

Â So, not irrigating this area out here has tremendous benefits to the farmer.

Â So, we can easily do this split application method.

Â It's much more difficult to do it with a center pivot.

Â And if we get around one time during the day that's probably about our limit.

Â But with drip irrigation, because we're irrigating small zones, we can separate

Â our field out into zones and we can control them with a computer, we can turn

Â that system on several times during the day and irrigate this, this particular

Â zone several times and that's easy to do with drip.

Â So, we know that with drip irrigation, we have now the capacity to take this system

Â and split it all up. And if we know the flow rate of our drip

Â tube, and I just chose one half gallon per 100 feet per day I mean per minute.

Â So, let me say that again. 0.5 gallons per 100 feet per minute as the

Â flow rate of our emitters and I just multiplied that out to an acre.

Â So, that half gallon emitter equates to about 35 gallons per acre per minute.

Â And we know we're going to put on 1,570 gallons.

Â And so, we divide by the flow, and our, our gallons per acre drop out of the

Â calculation, and we end up with minutes. And we can see that each of these

Â irrigation events, if it lasts 45 minutes, we will apply this much water which is

Â exactly what we need. And we repeat that three times during the

Â day. Remember, the plants are using water, the

Â irrigation or the water, the plant crop water amount is being used during the day.

Â And so, it makes sense to be able to split that up and apply, apply this much water

Â that was used during the early part of the day with one irrigation event and then,

Â the next portion of the water that's used with the next irrigation event, and, and

Â so on. And we have to kind of think a little bit

Â about when is the best time to start that first event, the second even, and the

Â third event based on the, the rate of water use during the day.

Â In other words, we'd probably would not want to put 2 of 3 irrigation events in

Â the morning. And so, you have to kind of think a little

Â bit about, most, most recommendations call for splitting those up during, during the

Â day. So, we would probably choose to, to

Â schedule maybe the first irrigation in the morning, and then the next irrigation

Â perhaps, maybe around noon or one o'clock in the, in the afternoon.

Â I'm using Florida, North Florida conditions in, in the summertime in the

Â spring and summer. And then, maybe a later application maybe

Â three or four o'clock later in the afternoon.

Â Our days are, are long and so an irrigation late in the afternoon is a very

Â effective and, and very good way to, to do it.

Â And then like we talked about with the sprinkler system, we're going to be

Â adjusting for, for rainfall. Now, with both of these systems now let's

Â just sort of step back and so we've, we've taken a look at the soil part of the of

Â the irrigation management strategy and we've identified that reservoir, we'll

Â call it that we want to manage for the, for the water for the crop.

Â We're going to let the crop use some water and then we're going to replace it back

Â based on the rate, the ET of the crop. And we've also looked at the crop and how

Â to calculate up during the growing season how much water is used.

Â So, if we factor those two things together, the ET of the crop, the water

Â demand or the use by the crop, and our ability to manage and handle and hold

Â water in our soil, then we have a very efficient way of managing irrigation

Â systems. And if we can account for rainfall, we can

Â put all of this information in a spreadsheet and we can manage it that way.

Â And more and more farmers now, because of the advent computers and access to

Â internet and the availability of this kind of these, these kinds of data today, more

Â and more farmers are now starting to use this, this method more than, more than

Â ever and it makes a lot of sense because irrigation and irrigation management are

Â costly inputs on the farm. And with the increased emphasis on water

Â quality and loss of nutrients with the expense of the nutrients, and the

Â environmental issues, and the fact that those nutrients, particularly things like,

Â nutrients like nitrate move with the, or with the water front, anything that we can

Â do to make increase our level of irrigation management is very, very

Â positive. Now, finally, we've done a good job with

Â all of this, but we'd still like to, to check ourselves and there's a couple ways.

Â We've talked about the blue dye as an indicator of where the water is in the

Â root zone, and we also talked about our soil moisture sensors.

Â This is a really good place to put our soil moisture sensors to work for us.

Â So, for example, if we have tensiometers and we're managing our irrigation by the,

Â the balance method or the checkbook method, if we have tensiometers placed

Â strategically in our crop, then we can watch what they're doing in reaction to

Â our irrigation management. So, for example, if we're maintaining

Â these, these two tensiometers in the range where they need to be for that, for sandy

Â soil, for example, then we know we're doing a good job up here and we can use

Â this to kind of check as it were. If this tensiometer, the deeper one, stays

Â too wet, then we know we're probably putting on too much too much water.

Â Maybe we got a rain, and we can't do anything about that.

Â But these two this placement of tensiometers can help us tell us, give us

Â some feedback as to how well we're doing with managing the water through the, the

Â checkbook method. And also, we can, we can use a dye.

Â This blue dye is easily obtainable from companies on the internet and it's called

Â marking dye. And you can put it into the irrigation

Â system or you can put it on the ground or you can put it in the, in the soil and

Â then you can watch the dye. So, here's an example I think I've shown

Â to you before. If we were managing our water and we had a

Â pattern like any of these out in the front, we're doing a pretty good job

Â because we're keeping, I'd like to see these closed up a little bit better but

Â this is very sandy soil and the chances are, it's going to go just as deep as fast

Â as it does wide. If you had a situation like this and you

Â were growing a vegetable crop with close spacings, you might want to increase the

Â spacing of the drip emitters on your drip tube, maybe go from 18 inches to 12 inches

Â for example. That would close up these patterns very

Â effectively. If we, if we were managing our irrigation

Â and we dug down and we saw something like this particularly if this blue area

Â extends down you know, deeper than, for sure, deeper than our root zone then we

Â know, we don't quite have our amounts of water calculated out correctly and we want

Â to, we want to readjust. So, these are two good systems to ground

Â truth and test what we're doing and help up adjust what we're doing.

Â Okay, so if we close up I just want to leave us with this notion again, we've

Â mentioned it several times throughout the course it's the water.

Â If we can keep the water in the root zone, then we can do a really good job of

Â keeping those mobile nutrients like nitrate in the root zone, irrigators need

Â to have tools to help them now. We can no longer practice irrigation every

Â third or fourth day by the, by the clock and that's not very efficient and we have

Â other issues and problems that we need to stay on top of notably water quality

Â environmental protection issues. So, having those kinds of tools, learning

Â how to use those tools is very important to become an efficient in water

Â management, management. So, irrigators also should know how to

Â apply some of these concepts that we've, we've talked about, how to mange these

Â soil moisture indicators, how to do some of the basic kinds of calculations to help

Â you understand, at least understand water holding capacity, available water holding

Â allowable depletion. Maybe you don't jump into checkbook right

Â away but at least understand some of the preliminary concepts and steps and work

Â yourself up to be able to, to do that. So, understanding something about the

Â soil, and understanding something about the crop water needs is critical to this.

Â And then, combining the, the water balance approach, the checkbook approach with a

Â soil moisture sensing device, gives us a really, really high level of capacity to

Â be efficient in our irrigation management. And again, just to let you know that there

Â is a lot of information on the internet about these irrigation systems and

Â methods. And you need to spend some time learning

Â about them through those resources that are out there but you need to ground truth

Â them with the experts and the specialists in, in your particular area.

Â