Recent Rains Meet Final Crop Water Needs at Monitoring Sites

Recent Rains Meet Final Crop Water Needs at Monitoring Sites

 Sept. 7, 2011

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This season follow the crop water monitoring and irrigation decision-making for two eastern Nebraska fields — one near York and one near Mead. Each week Gary Zoubek, extension educator in York County, will provide soil water monitoring information for two fields through podcasts, photos and updates in CropWatch.

Late season soybeans turning to yellow

As soybeans in the York area started to turn yellow, rains helped replenish the soil water profile so further irrigations won't be necessary.  (Photo by Gary Zoubek)

This week was similar to the last two in that crops in eastern Nebraska have continued to mature, but now at a little slower rate. Water use has been about the same, averaging a little over 1.10 inches for the week or about 0.16 inches per day. The corn fields being monitored are in full dent stage with the milk line about three quarters down. Soybeans are in the full seed or R6 stage with leaves beginning to yellow or the R6.5 stage.

This past week high temperatures in York ranged from 72° F to 95° F and averaged 87° F. Humidity dropped some more and varied from 69% to 88%, averaging 77% for the week. Conditions near Mead were similar with high temperatures averaging 86° F and humidity averaging 75% for the week.

The ETgages near York dropped 1 inch for the week. We received about an inch of rain for the week! Last week the corn grower plot sensor readings were 73, 59, 125 and 33 for a depletion of 2.10 inches. Corn was at one-half milk line so the 1.9 inches of water remaining in the soil profile was a little short of what was needed. The inch of rain received was just what the doctor ordered. The readings this week are 23, 31, 119 and 47. The decision to delay irrigation for a couple of days paid off and now we’re finished irrigating for the season.

The other corn fields being monitored have readings varying from the 30s to the 70s and are all in good shape and finished for the season. The soybean field being monitored has leaves that are starting to yellow. Between the rainfall last week and irrigation the week before, all the sensors are now reading below 50 so we’re finished for the season!

A Look Back Over the Irrigation Year

In summarizing this past year’s data from May 16 to September 4, the greatest weekly ETgage drop was 2.15 inches in early June; however, at that time the crop was at the V4 stage so crop water use was only 0.39 inch for the week. The largest weekly crop water use was 1.60 inches July 18-24, an average 0.23 inch per day.

The ETgage dropped about 20 inches for the year and when we factor in the various crop growth stages, the estimated corn water use or ET was 15.5 inches for the year. Total rainfall for the season in the York area was approximately 18-20 inches. Data from the High Plains Regional Climate Center was similar, with an estimated crop water use or ET of 17.6 inches for the season. See Table 1 for a week-by-week review of how this irrigation season progressed.

Table 1. 2011 Summary of weekly crop water use (ET) at a corn field being monitored near York.

  Date HPRCC
Potential ET
Crop ET
ETgage Crop ET Crop Stage
Week 1 5/16-5/22 1.54 0.15 0.70 0.07 V1
Week 2 5/23-5/29 1.08 0.15 0.70 0.10 V3
Week 3 5/30-6/5 2.35 0.42 2.15 0.39 V4
Week 4 6/6-6/12 1.94 0.68 1.90 0.67 V6
Week 5 6/13-6/19 1.62 0.68 1.35 0.57 V7
Week 6 6/20-6/26 1.23 0.74 0.95 0.57 V9
Week 7 6/27-7/3 2.02 1.78 1.60 1.41 V12
Week 8 7/4-7/10 1.57 1.57 1.30 1.31 V14
Week 9 7/11-7/17 1.54 1.54 1.35 1.49 Tassel
Week 10 7/18-7/24 1.76 1.76 1.45 1.60 Silking
Week 11 7/25-7/31 1.41 1.41 1.25 1.38 Brn Silk
Week 12 8/1-8/7 1.38 1.38 1.05 1.16  
Week 13 8/8-8/14 1.48 1.48 1.20 1.32 Full Dent
Week 14 8/15-8/21 1.06 1.06 1.00 1.10  
Week 15 8/22-8/28 1.32 1.32 1.00 1.10 60% Milk Line
Week 16 8/29-9/4 1.43 1.43 1.00 1.10 90% Milk Line
Season Totals


Catch up with Previous Podcasts

This is the 14th in a series of irrigation management podcasts for eastern Nebraska from Gary Zoubek.  Hear more about irrigation management at this growth stage in the podcast (above) or view the podcast transcript.

Also see:

Gary Zoubek
Extension Educator, York County


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A field of corn.