Weekly Irrigation Newsletter — Irrigation Scheduling Update for July 28, 2025

Steve Melvin Author

07/29/2025 Added

6 Plays

Description

Nebraska Extension Educator Steve Melvin demonstrates how to apply the irrigation scheduling method outlined in "Irrigation Scheduling Strategies When Using Soil Water Data" (Nebraska Extension NebGuide EC3036). (Video No. 2 of series)

Searchable Transcript

Search:

[00:00:00.000]Hi, this is Steve Melvin,
[00:00:08.000]Extension Educator with the
[00:00:09.280]University of Nebraska
[00:00:10.230]Extension and this is
[00:00:11.960]the July 28th week of
[00:00:13.940]irrigation scheduling updates.
[00:00:16.630]You'll probably hear a little
[00:00:18.880]extra
[00:00:19.440]noise in the background today
[00:00:21.210]because around my office is the
[00:00:22.890]Merritt County Fair going on
[00:00:24.640]and certainly makes for a
[00:00:25.790]little more noise in the office
[00:00:27.220]than other weeks. The
[00:00:30.760]procedures we're
[00:00:32.080]going to go over are more
[00:00:33.610]completely laid out in EC 3036
[00:00:36.240]which you can find the link to
[00:00:38.180]that in the
[00:00:39.340]irrigation newsletter in a crop
[00:00:41.450]watch this week or if you'd
[00:00:43.050]rather listen to videos you can
[00:00:44.990]find
[00:00:45.340]a nice five-part video series
[00:00:46.890]describing the procedure in
[00:00:48.410]more detail as well. The corn
[00:00:52.520]again
[00:00:52.840]is at South Central Ag Lab.
[00:00:54.640]by Clay Center. It was planted
[00:00:56.690]on April 22nd, 117 day variety.
[00:00:59.660]We've got two
[00:01:00.560]inches per week that we're
[00:01:02.110]limiting ourselves to on
[00:01:03.600]irrigation capacity. In
[00:01:05.320]other words, we can only apply
[00:01:06.960]two inches per week. Clay
[00:01:08.410]Center area gets about 28
[00:01:10.080]inches of rainfall per year.
[00:01:12.600]The corn is at the R2 stage and
[00:01:15.070]we're using watermark
[00:01:16.840]sensors with data loggers from
[00:01:19.940]Eurometer. The corn is in the
[00:01:22.570]blister stage and you
[00:01:25.480]can see that the root zone
[00:01:26.560]should be about three and a
[00:01:27.690]half feet, but I
[00:01:28.600]typically this time of year
[00:01:29.870]limit myself to three feet to
[00:01:31.180]be just a little bit
[00:01:32.200]more conservative. Crop water
[00:01:35.580]use is about 0.26 inches per
[00:01:39.080]day or 1.82 inches
[00:01:40.780]per week and that's a good
[00:01:42.810]number for blister. You ask how
[00:01:46.280]come it
[00:01:46.820]is dropping off this quickly
[00:01:48.020]because sometimes we end up
[00:01:49.360]with some really hot
[00:01:50.240]weather here the end of July.
[00:01:53.040]Well keep in mind that the days
[00:01:55.330]are getting
[00:01:56.020]shorter. We've already lost
[00:01:57.480]about 40 minutes of daylight
[00:01:59.420]from the longest day
[00:02:00.440]of the summer and we're losing
[00:02:02.250]about two minutes per day. So
[00:02:05.380]in other words, by
[00:02:06.100]this time next week it'll be
[00:02:07.410]about 14 days less daylight
[00:02:09.320]than we have now. So
[00:02:10.160]you can see this continues to
[00:02:11.780]drop off. Then once we get on
[00:02:13.480]down here of course
[00:02:14.360]the corn starts to senesce and
[00:02:16.280]mature, but
[00:02:16.800]for now this is mostly related
[00:02:18.670]to day length. So we get the
[00:02:22.940]numbers. We had 34
[00:02:25.680]centibars at the top foot, 53,
[00:02:27.810]22, and 30 and we're not going
[00:02:30.100]to use the fourth
[00:02:30.940]foot yet because we're right in
[00:02:33.310]this sensitive stage of our
[00:02:35.420]corn. We're going
[00:02:36.480]to use a three foot root zone
[00:02:38.080]and not this sensor down at 42
[00:02:40.020]inches. So if we
[00:02:41.560]place those over here you can
[00:02:43.480]see that the third foot is up
[00:02:45.320]under at 20 and at
[00:02:46.780]40 inches. This probably
[00:02:48.510]indicates that we you know got
[00:02:49.880]things a little wetter
[00:02:51.280]than maybe we should have this
[00:02:52.660]past week. And the other two
[00:02:54.000]sensors are here in
[00:02:54.760]this range storage zone. So if
[00:02:56.280]we think about it you know we
[00:02:57.760]probably look at
[00:02:58.660]that and go well hey we
[00:02:59.680]probably don't need to irrigate
[00:03:01.310]too much this week. But
[00:03:02.380]let's go on and take a look at
[00:03:03.570]these next two column of
[00:03:04.640]numbers and see if we
[00:03:05.660]can get a little more insight
[00:03:07.200]into what we might decide to do
[00:03:08.820]this week. This is
[00:03:11.620]a chart that was downloaded
[00:03:13.000]from the data logger that's on
[00:03:14.500]there. You can see this past
[00:03:16.760]week we put the two
[00:03:16.760]inches on and then you can see
[00:03:18.870]that as we ended up with the
[00:03:20.710]soil being quite a
[00:03:26.480]bit wetter than it was
[00:03:30.010]previously. In fact the top
[00:03:31.740]foot and third foot ended
[00:03:33.660]up here really wet. The second
[00:03:36.020]and fourth didn't really change
[00:03:37.860]too much but this
[00:03:39.140]one down at 42 inches you can
[00:03:40.840]see it came up and got a little
[00:03:42.380]bit above
[00:03:42.740]field capacity. So we may even
[00:03:44.500]have ended up putting on a
[00:03:45.830]little too much
[00:03:46.740]water and deep perking some.
[00:03:48.640]This past week we had forecasted
[00:03:50.610]we'd use two
[00:03:51.300]inches of crop water use but in
[00:03:53.060]reality it all got measured and
[00:03:54.900]said and done
[00:03:55.560]because it was so humid this
[00:03:56.850]past week it only ended up
[00:03:58.050]being about an inch and
[00:03:59.100]a half. So you can see we ended
[00:04:00.460]up putting a little more water
[00:04:01.770]on than we
[00:04:02.520]probably really needed to. Okay
[00:04:06.450]so the next column over here is
[00:04:08.620]percent of
[00:04:09.260]plant available water. You can
[00:04:10.840]see at field capacity it's 100
[00:04:12.580]percent and as
[00:04:13.380]the soil would get wetter and
[00:04:14.970]wetter you see that goes above
[00:04:16.720]a hundred
[00:04:16.720]percent. This third foot sensor
[00:04:18.760]down here is a hundred and
[00:04:20.090]thirteen percent
[00:04:21.000]and this is for a one foot zone
[00:04:23.220]of soil. As we get start using
[00:04:25.680]that water and get
[00:04:26.560]below drier than field capacity
[00:04:28.650]you can see that the numbers
[00:04:30.420]are less than a
[00:04:31.060]hundred percent. And so if we
[00:04:32.550]take these three numbers the 113,
[00:04:35.440]93, and 77 put
[00:04:37.060]them over here in the order
[00:04:38.730]they're in add those numbers
[00:04:40.580]together and now we
[00:04:41.600]can compare the three and we
[00:04:45.030]can divide by three.
[00:04:46.700]And see that it's 94 percent of
[00:04:48.670]plant available water. So how
[00:04:52.840]much water could
[00:04:53.880]we put on? How much irrigation
[00:04:55.630]or rain without going to bring
[00:04:57.270]it up to field
[00:04:57.940]capacity? So we can see if we
[00:05:00.070]take this 94 the closest we've
[00:05:01.990]got to that is 93
[00:05:03.160]so point one seven inches of
[00:05:05.100]water and over the three foot
[00:05:07.010]profile since it's
[00:05:08.120]an average we can see that if
[00:05:09.550]we put on one half inch of
[00:05:10.790]water it would bring
[00:05:11.940]this soil profile back up to
[00:05:13.670]field capacity. So we don't
[00:05:15.550]have a lot of room to
[00:05:16.680]put water on before we would be
[00:05:18.430]above field capacity which we
[00:05:20.180]certainly don't
[00:05:21.240]want to do with irrigation. So
[00:05:23.570]how much water have we got
[00:05:25.360]remaining? So if we take
[00:05:26.940]from where we're currently at
[00:05:29.890]at this point negative one
[00:05:32.560]seven in other words
[00:05:33.500]it would take that half inch
[00:05:34.820]remember to fill it but on a
[00:05:36.720]foot amount that's
[00:05:38.460]point one seven and we might
[00:05:40.390]use it down to sixty percent
[00:05:42.330]this time of year I
[00:05:43.260]really don't like to go clear
[00:05:44.710]to fifty percent because if
[00:05:46.240]anything goes
[00:05:46.660]wrong with the with the center
[00:05:48.430]pivot or with the irrigation
[00:05:50.140]pump or anything I
[00:05:51.500]like to have just a little bit
[00:05:52.760]of buffer down here so stop at
[00:05:54.560]sixty percent so
[00:05:55.720]that's point nine three you can
[00:05:58.100]see if we these are negative so
[00:05:59.960]when you
[00:06:00.160]subtract two negatives we're
[00:06:01.500]coming up with the amount of
[00:06:02.570]wet water that's
[00:06:03.340]between these two would be a
[00:06:04.780]positive number
[00:06:05.620]it's point seven six inches per
[00:06:08.070]foot times our three foot root
[00:06:10.490]zone we've got
[00:06:11.660]two point two eight inches of
[00:06:13.200]water remaining before we would
[00:06:15.010]dry this soil profile on
[00:06:16.640]average down to this sixty
[00:06:19.410]percent of plant available
[00:06:23.750]water. So the next
[00:06:24.140]question we want to get at is
[00:06:25.860]how many days could we use that
[00:06:27.660]water before we
[00:06:28.700]would run out and if you take a
[00:06:31.180]look it was point two six is
[00:06:33.010]what we had so eight
[00:06:35.360]point eight days is the amount
[00:06:37.220]of time that it would take on
[00:06:39.050]the average use
[00:06:40.280]water use is point two six per
[00:06:42.420]day to get down to that level
[00:06:43.870]so you can see
[00:06:44.360]we're in good really really
[00:06:45.970]good shape
[00:06:46.620]with the amount of water that
[00:06:48.060]we have stored in our soil
[00:06:49.640]profile. So what are
[00:06:51.780]we going to decide to do this
[00:06:52.930]week again we've got two inches
[00:06:54.090]that we can apply
[00:06:54.780]with our irrigation system we're
[00:06:56.830]predicting from long-term
[00:06:58.080]averages we'd
[00:06:58.800]only use one point eight two
[00:07:00.490]right now we're only a half
[00:07:02.210]inch below field
[00:07:03.660]capacity so we really can't get
[00:07:05.240]real busy this week and put a
[00:07:06.630]lot of water on
[00:07:07.560]or we'll overfill the profile
[00:07:09.100]and plus it's
[00:07:10.380]saying that it's going
[00:07:11.660]to be cool and a good chance of
[00:07:13.350]some rain later this week so I'm
[00:07:15.220]thinking this number will
[00:07:16.600]probably be quite a bit lower
[00:07:18.280]because at the end of the week
[00:07:19.460]supposed to be
[00:07:19.960]really cool and cloudy and
[00:07:21.690]chance of showers and things
[00:07:22.940]all week and so I'm
[00:07:23.980]thinking this might only be an
[00:07:25.290]inch and a quarter or something
[00:07:27.030]this week again
[00:07:27.880]you're always kind of
[00:07:28.890]predicting into the future so
[00:07:30.320]what I'm planning to do
[00:07:31.280]this week is apply one inch of
[00:07:32.960]irrigation water and since
[00:07:34.440]there's a
[00:07:34.840]pretty good chance of rain in
[00:07:36.780]two nights I'm going to wait
[00:07:38.330]until Wednesday I'm
[00:07:39.340]recording this on Monday so we'll
[00:07:40.880]wait till Wednesday and then
[00:07:42.840]out of this one
[00:07:43.420]inch amount that I want to
[00:07:44.790]apply this week we'll subtract
[00:07:46.580]out any rain that we might get
[00:07:48.540]and go from there so for now
[00:07:50.210]this is Steve
[00:07:50.960]Melvin extension educator with
[00:07:52.310]the University of Nebraska
[00:07:53.480]signing off from
[00:07:54.620]the irrigation scheduling
[00:07:56.650]webinar that I'm putting
[00:07:58.530]together and we'll catch you
[00:08:00.320]again next week

The screen size you are trying to search captions on is too small!

You can always jump over to MediaHub and check it out there.

Comments

0 Comments

Weekly Irrigation Newsletter — Irrigation Scheduling Update for July 28, 2025

Description

Searchable Transcript

Comments icon comment

Related Channels

Comments