Scheduling Irrigation using an Atmometer- August 2012
[University of Arkansas Division of Agriculture Research and Extension University of Arkansas System. Arkansas Soybean Promotion Board. Chris Henry, Ph.D., P.E., Assistant Professor and Water Management Engineer, Rice Research and Extension Center.]
[Video shows a soybean field. Dr. Henry is speaking to a group in the field.] On this field here we’re looking at how we irrigate soybeans. This is also part of the research verification program. We split the field in half, and in two divisions. One, we’re using Arkansas irrigation scheduler following the research verification program recommendations, and the other side, the only difference we made is we are using an atmometer to schedule the irrigation on the other side.
[Video shows an atmometer] An atmometer is a really nice tool to help understand soil evapotranspiration, so I’ve got the atmometer up here. We’re working on ... I have some of these charts, I’ll just pass them around, you can just kind of look at them, but, here let me have one. [Video shows charts.] Basically you look up what kind of soil you have and then you reference off the stage of crop growth and set your deficit. [Dr. Henry shows an atmometer and passes it around for others to see.] That’s our trigger point for irrigation.
And these basically have to have a canvas and ceramic plate on top and this has been developed to mimic the evapotranspiration from the leaf surface. So this is experiencing the same E.T. that the plant is, so that’s basically what it’s doing. So here we started it, after we irrigated last, it was full and we haven’t had a lot of E.T. and when the liquid level gets to this mark, that’s our trigger point for irrigation. So if it rains, just say it rains a half inch and it all went in, we would just slide our ring down a half inch to account for that precipitation. If it rains a lot more than that and some of it ran off, you have to make a judgment call about how much.
But it really lets you know where you’re at in the soil profile when your trigger point is next for your irrigation. So this is one technique that we’re using that we’re piling to see if it’s different than the Arkansas irrigation scheduler which has been around since the mid eighties.
[Video shows a soybean field. For additional information on this topic and more visit our website at www.uaex.edu.]