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Soil Moisture 5-10-18

The area of ‘abnormally dry’ or ‘moderate drought’ was reduced by 5% in Nebraska as of 5/8/18 compared to the previous week.

Bladen 5-10-18

This site has continually missed the rain.  The first foot can be observed as slowly drying out as  well this week with total soil moisture (1-4′) remaining above 50% depletion.  This site was removed due to corn being planted in this field.  

Byron 5-10-18

Last week’s rains did help the first and second feet remain below field capacity.  However, the third foot did not remain wet after the rainfall event and can be seen climbing in depletion in the graph this week.  I did probe this site this week and there appears to be good moisture now just past 2 feet, but it gets dryer after that.

Lawrence 5-10-18 Corn

This site continues to remain steady with total soil moisture depletion around 35%. 

Lawrence 5-10-18 Soy

The first foot sensor has leveled off after being reprimed on 4/26.  Total soil moisture depletion (1-3′) remains around 45%. 

Superior 5-10-18

Last week’s rains helped with the first foot and somewhat with the second foot at this site.  Total soil moisture depletion is around 40%.

Soil Moisture 5-3-18

Today was interesting driving my route through the southern tier of counties I serve.  Wearing overboots and walking instead of driving to the sensors was welcome at Byron and Superior where heavier rain events occurred this week.  However, Lawrence and Bladen had largely missed the rains.  The Clay Center location received 1″ the past two days, but other areas of Clay County received very little.  The farmers who have allowed me to monitor pre-plant soil moisture thus far were interested in watching this throughout the growing season.  Thus, sensors will remain in most of these fields.  Where fields have been planted thus far (other than Clay Center), planters have planted around the sensors and seeds have been hand-planted between sensors.

Drought Monitor 5-1-18

The Nebraska Drought Monitor Map updated 5/1/18 (before the rain events the past few days) showed expanded areas of ‘abnormally dry’ (yellow) and ‘moderate drought’ (tan).  Stars show the locations of soil moisture monitoring equipment.

Bladen 5-3-18

This location essentially missed the rains this week with the top foot remaining around field capacity and 2-4′ near 40% depletion or above.  Wheat near this location had jointed but was shorter than at Lawrence and Superior.

Byron 5-3-18

This location has been interesting to monitor.  Last week I mentioned that moisture received wouldn’t be enough to maintain the second foot near field capacity after 4/26 (which is true from the climb observed in the second foot).  This location received 1.5″ the past two days. With the top foot at field capacity, it makes sense that today it is showing near saturation with the second foot dropping below field capacity as well.  I should have probed the soil to see if moisture truly reached the third foot or not.  The chart shows the third foot also filling below field capacity.  We will know more from next week’s graphs.  Being a no-till field, the rain soaked in well even though it appeared to come hard from the way the road had washed in spots and was super soft.

Lawrence 5-3-18 Corn

This location received some misting as I was collecting this data, but the sun soon came out and steam began rising from this field and the soybean field across the road (next graph).  Essentially 0.05″ of rain was received at this location and the graph remained unchanged this week for the most part other than increasing soil temperature.

Lawrence 5-3-18 Soy

At this soybean location, something had caused for a disconnection in the 1st foot sensor last week, so I reprimed the sensor on 4/26.  I didn’t take out the first 48 hours in this graph (which we say is normal time to acclimate to the soil).  The first foot is currently showing over 15% depletion this week with total soil moisture depletion near 50%.  

Superior 5-3-18

This location received 1.25″ of rainfall the past few days which helped the second foot recharge to near field capacity and the total soil moisture (1-4′) be near 35% depletion.  Wheat near this location had jointed and elongated a great deal compared to last week.

Beginning Soil Moisture 4-26-18

Some rains helped with the top foot profile at some of these locations last week. One thing to keep in mind when viewing these graphs is we don’t always know what’s going on below the soil surface. One farmer had a good point regarding my “blips in the graphs” in my last blog post. I mentioned they could be due to a soil crack along the PVC pipe-which we do see occur and can be true. However, he also had a good point that it could be a worm hole, root channel, etc. that water may have followed for a brief time period, which could also be true, especially in these long-term no-till fields. As you look at the charts this week, it’s important to keep in mind that soil water also moves via gravity (termed ‘gravitational water’). Thus, sometimes why we can see changes in soil moisture in the successive drier layer with small amounts of precipitation.

Drought Monitor 4-26-18

Nebraska Drought Monitor as of 4/26/18 showing increasing ‘abnormally dry’ areas of the State.  The ‘moderate drought’ area has expanded further into Webster and Thayer counties.  Stars show locations where I’m taking pre-plant soil moisture status.

Bladen 4-26-18W

Beginning soil moisture at Bladen remained relatively unchanged last week.  The top foot went back to around field capacity with some rain events.  Total soil moisture depletion is above 50% at this site as are all soil layers from 2′-4′).

Byron 4-26-18

Moisture last week did appear to re-wet the top 2 feet.  I even probed the soil in the same area to ensure there was truly moisture in the second foot, which there was.  Yet as you can see from the graph, the second foot was starting to climb when I took these readings. My guess is without additional precip, the second foot will be above field capacity again next week.

Clay Center 4-26-18

Because the top two feet were already around field capacity, gravitational water along with moisture received last week may have created the dip in the third foot readings seen over a few days.  It was rising back up to above 50% completion on 4/26.  The sensors were removed on 4/26 as the field was planted to soybean that day.

Lawrence 4-26-18 Corn

This location received 0.20″ of rain last week with essentially no change in soil moisture status from the previous week.  Total soil moisture (1-4′) is steady around 35% depletion.

Lawrence 4-26-18 Soy

This location also received around 0.20″ of rain last week.  Something happened to create a short in the top foot sensor, thus, the lack of data for 1′ and total (1-3′) after 4/22.  It was fixed on 4/26.

Superior 4-26-18

This location received around 0.60″ of rain last week.  The top foot remained steady and there was a gradual decrease followed by increase in soil moisture in the second foot.  This would make sense from the combination of gravitational water and the precipitation moving through the first foot into the second, but the moisture wasn’t enough to maintain the second foot at a wetter moisture level.

Beginning Soil Moisture 4-19-18

Here is an update on beginning soil moisture status. The left charts are as of 4/19/18 with the right charts being the previous week. You can click on the images to enlarge them. The ‘weekend moisture’ event I refer to was the blizzard 4/14/18.

Nebraska map

Bladen: The top foot is now slowly losing moisture one week later in spite of some weekend moisture. The second-fourth feet are all above 50% depletion.

Byron: Some weekend moisture may have allowed the top foot to remain steady.  The second and third feet are both over 50% depletion bringing the total soil moisture in the 1-4′ depths closer to 50% depletion. There must have been a soil crack along my PVC pipe to allow for the moisture spike you see in 3 and 4 feet and not 1 and 2 foot depths.


Clay Center: This is still the wettest location in spite of the top foot slowly drying out this week.  The second foot is still below field capacity with third and fourth feet and total soil moisture relatively unchanged. Must have had a soil crack along PVC pipe for third foot for the quick dip observed.


Lawrence Corn Stubble: Minimal change was observed at this location this past week.  Essentially all feet remained the same in regards to soil moisture.  A small crack along PVC pipe must have been present at 3 foot for short dip observed there.


Lawrence Soybean Stubble: This location (across road from corn stubble) showing dryer than last week. Top two feet now dryer than field capacity which increased the total (1-3′) soil moisture depletion.


Superior: Weekend moisture may have allowed the top foot to stay steady (as was also seen in Byron).  However, the second, third, and fourth feet all lost moisture leaving the total soil moisture (1-4′) above 35% depleted at this location.

Beginning Soil Moisture 4-11-18

The current Drought Monitor shows 19% of Nebraska in the “abnormally dry” or “moderate drought” categories and in the shadow of large-scale drought in Kansas (97%) and Colorado (88%). Being curious about beginning soil moisture in non-irrigated situations, I installed Watermark soil moisture sensors in six non-irrigated, no-till locations in Webster, Nuckolls, Thayer, and Clay counties.

Nebraska map

Nebraska map showing moderate drought (tan) and abnormally dry (yellow) areas of the state with locations of soil water sensors indicated by red stars.

Purpose

This quantitative information can be helpful as growers make planning and planting decisions. Granted, most planting decisions have already been made with inputs already purchased. Spring rains are also typically expected. However, information like this can help a grower be flexible in that planning should anticipated rains not be timely.

  • The grower may choose to plant a more drought-tolerant crop like sorghum or a more drought-tolerant corn hybrid.
  • A grower with livestock may choose to plant a feed/forage crop.
  • A grower may choose to not terminate a growing cover crop such as rye, instead growing it for feed.

Process

Soil moisture sensors were installed at 1-, 2-, 3-, and 4-foot depths in non-irrigated, no-till corn and soybean residue fields near Byron, Superior, Lawrence, Bladen, and Clay Center. The sensors were connected to Watermark dataloggers from the Irrometer company. Because the default soil temperature on the dataloggers is 70°F, a temperature sensor is also installed to ensure correct calibration of the soil moisture. This is because soil temperature during this time is dfferent (much lower) than 70°F.

Any farmer or crop consultant could do the same for his/her fields to determine the same information and wouldn’t need the datalogger. Taking weekly readings at the same time each week, or even daily at the same time, would also give one an idea of beginning soil moisture. It’s best to allow at least 48-72 hours for the sensors to equilibrate to the current soil moisture conditions. This process is essentially the same as when sensors are installed for irrigation scheduling. The difference is these are non-irrigated fields with no current crop growing. For additional information and videos on using watermark sensors, please see the Nebraska Agricultural Water Management Network website.

Other Observations

Nuckolls County is shown as in “moderate drought” on the Drought Monitor. At the Superior location, we were hoping to also install into actively growing rye and winter-killed forage to determine beginning soil moisture in those conditions. The rye is currently 6 inches tall in the tillering stage and the soil probe wouldn’t go in the ground beyond 6 inches, so no moisture sensors were installed. The soil probe would only go in 12 inches in the winter-killed forage consisting of sorghum-sudan and radishes; thus, soil moisture sensors weren’t installed in that field either.

Results so Far

During installation, the 3- and 4-foot depths at all locations (only 4-foot at Clay Center) seemed very dry. The soybean residue appeared drier than corn residue. Two sites are located near Lawrence, one in corn residue and one in soybean residue across the road from each other. That data shows differences in moisture between different residue types the most clearly. I was unable to install to the 4-foot depth at the Lawrence soybean residue location. At most other sites, a hammer was used to help install to 4 feet. However, given the difficulty in installing the 4-foot sensor, these graphs do not show them as dry or drier than the 3-foot at any location other than Bladen.

This could be due to several reasons:

  • The soil textural properties at 4-foot depth could have more clay and higher soil bulk density in which the drier conditions would not be obvious or easily determined just by installation difficulty.
  • There could be a compacted layer.
  • The dryness or wetness of any given soil layer at any given time is a function of various factors including the farming history of the field, previous several years of root development in different layers, previous year’s precipitation amount and distribution during the season as well as during off-season, evaporation rate, and water uptake pattern of the crop from different soil layers as water update from different soil layers varies and also varies with time during the season.
  • The 4-foot layer may not actually be drier than the 3-foot layer.

Because only a few days of data are shown thus far, it is difficult to make a determination at this time. Data will continue to be collected until each field is planted and the results will be posted weekly on my blog. Additional information regarding each location is in each figure caption.

A special thank you to each farmer cooperating with me on this effort and to Dr. Suat Irmak for providing additional equipment and advice on this effort.

Bladen

Soil moisture for top four feet in non-irrigated, no-till corn stubble near Bladen. Total soil moisture is currently depleted above 50% at this location.  Notice even the second foot is above 50% depletion.  The third and fourth foot follow the same line.

Byron

Soil moisture for top four feet in non-irrigated, no-till soybean stubble near Byron. Total soil moisture is currently depleted around 42% at this location.  The second foot is also approaching 50% depletion at this site.

Clay Center

Soil moisture for top four feet in non-irrigated, no-till corn stubble near Clay Center. Total soil moisture is currently depleted around 30% for this location.

Superior

Soil moisture for top four feet in non-irrigated, no-till corn stubble near Superior. Total soil moisture is currently depleted around 30% for this location.

Lawrence corn

Soil moisture for top four feet in non-irrigated, no-till corn stubble near Lawrence.  Total soil moisture is currently depleted around 37% for this location.

Lawrence Soy

Soil moisture for top three feet in non-irrigated, no-till soybean stubble near Lawrence. Total moisture in these three feet is currently depleted around 37% for this location. Only three feet were installed as I didn’t have a drill to install the fourth foot.

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