Coming Events
- July 22, Extension Board Meeting, 7:00 p.m., Extension Office, York
Cropping Update
Crops have continued to make good progress! We could sure use a good general two day rain rather than these hits and mostly misses. We only received .03†for the week! As I had indicated last week, we’re seeing lots of tassels just starting to peak through and many of the soybeans are at R2 with a few nearing R3.
The ETgages I monitor in York, east of town as well as south of town, dropped about 1.70†for the week compared to 1.90†the week before. The humidity helped keep the drop down a little and we could really feel the humidity on several days.
Much of the early corn is at V14, so the factor is 1.01 while it the corn is at V16 or silking, the factor is 1.10.
To estimate the crop water use for V14 corn, we simply multiply 1.7 x 1.01 so our crop water use was 1.72†for the week or .25â€/day.  V16 corn would be using 1.7 x 1.1 or 1.87†or .27â€/day.
I’m also monitoring some fields that we’ve placed Watermark sensors in both corn and soybeans. The two corn fields had sensor readings of 65, 69, & 25 at the 1, 2, and 3 foot depths, while the other had sensor readings of 77, 59, and 9 at the same depths it happens that both field have depleted 1.10†of water with about 2.20†still left in the profile. These producers are planning to wait a day or two and then if no rain apply an inch or so. It’s important to leave a little room in case we do get that needed rain.
The York County Corn Grower Plot readings are 74, 80, and 1, so they’ve depleted about 1.33 inches of soils from the top two feet and have .86†left in the top two feet before they’ve depleted it to 50%. They also have a full profile in the third foot.
The sensors in the York County RoundUp Ready soybean plot are reading 110, 74, 24, and 27, so we’ve depleted 1.5†and have 1.78†remaining before we get to 50% depleted.
I’ve received questions as to what sensor reading should I have to decide when to irrigate. The key is to know your capacity. If you’ve got good wells and systems that work well, you can let the sensors get dry, but if you have low capacity wells, that’s a different story. Also, the better the soils the more flexibility you have.
The first thing you need to do is calculate your gross system capacity. You do that by dividing your pump capacity by the acres you irrigate. So if you have a well that pumps 750 gpm on 125 acres that’s a gross capacity of 6 gpm/acre. We have charts for Eastern and Western Nebraska, and since Western Nebraska receives less rain and is more aired, they have large capacity needs. With our good Hastings Silt Loams soils our needed capacity is 3.9 gpm/acre to get by 9 of 10 years and to meet peak need, we need a capacity of at least 5.71 gpm/acre.
So in our area if you have a well that’s pumping 871 gpm you can meet the peak needs of 5.7 gpm/acre on 130 acre field.
If you have sensors installed in your field and have any questions about the readings, give me a call at 402-362-5508 or 402-326-8185 or email me at gary.zoubek@unl.edu. I’d be glad to visit with you about them and what the numbers mean. You could also download our Crop Water App for iPads/iPhones at: http://go.unl.edu/aiz or forAndroids at: http://go.unl.edu/hkg.
With this app you can simply type in your sensor readings and soil type and get the water used as well at the water available. I hope you’ll check it out and let me know how it works!
