This is Aaron Nygren, your local agronomist with Nebraska Extension in Colfax, Cuming, and Stanton counties. Today I would like to share some results from research conducted this past summer at Soybean Management Field Day sites across Nebraska. One change at last year’s Soybean Management Field Days was that all the sites were planted the previous fall to cover crops, with resulting plots of rye, wheat, and a control with no cover crop. Today I want to focus on one study that I helped conduct that looked at differences in soil water content.
One common question with cover crops is how much stored soil water are they going to use that then might not be available to the following cash crop. The study examined this question by measuring soil water content at 6, 18, and 30 inches in both the rye and control plots with four replications at each site. To give a little background, sites were located on irrigated fields near Albion, Cedar Bluffs, Hartington and Kenesaw. Unfortunately, the Hartington site was lost to a hailstorm on July 18th.
As you may remember, last year’s weather was not great for early season cover crop growth, so the decision was made to delay planting to maximize cover crop growth, resulting in planting finishing up around June 1st.
So, what effect did we see on soil water? At planting time, all of the sites had statistically significant differences in soil water, with the cover crop plots having anywhere from 1.2 to 2.4 inches less water in the 3 foot profile. However, only one site, Kenesaw, had cover crop plots that were below field capacity, so drier soils in the cover crop plots may have actually helped planting conditions and likely reduced deep percolation of water into the profile.
After planting, rainfall exceeded crop water use, resulting in only one site having a significant difference in soil water content on the day that the soils were wettest. However, this difference was minimal as both plots were still well above field capacity.
Let’s wrap up with some take home points. First off, irrigation can allow you to manage cover crops differently, as you likely start the fall with a wetter profile and you have flexibility to water the crop if needed. Secondly, in Eastern Nebraska, early season rains in May and June will likely exceed crop water use, resulting in recharge of the soil profile, minimizing the effect of water used by the cover crop. This is especially true for soybeans, which have a later critical period for water than corn.
To learn more about this research and other studies, soybean growers should watch your mailbox in the coming months for a printed report, thanks to your investment in the Nebraska Soybean Checkoff.
To listen to this radio message again or to get more information, visit our local website at croptechcafe.org or give me a call at 352-3821. This is Aaron Nygren, your local agronomist for Nebraska Extension on KTIC radio.
