No Till Notes - “Winter Wheat Water Use Efficiency, part 2”

By Mark Watson, Panhandle No-Till Educator
I want to remind everyone of the No till On the Plains Whirlwind Field Day on August 28, 2012 in Alliance, Nebraska. The field day will begin with registration at the Knight Museum and Sandhills Center at 8:00 a.m. Hope to see you there. If you have any questions feel free to call me at 308-760-5259.
I shared with you our winter wheat yields from this past harvest in a previous article and I wanted to visit a little more looking at our yields and the water use efficiency we saw with our winter wheat crop. We harvested between 43-51 bushels per acre this year. For the time period between July of 2011 and the end of June, 2012 we received 13.05 inches of precipitation which is 2.15 inches below normal.
Research on water use efficiency in winter wheat I have read show dry land winter wheat to require 5.2 inches of precipitation for vegetative growth. For each additional inch of moisture the winter wheat will produce 4.7 bushels of wheat. Using our precipitation recorded over the past year of 13.05 inches of precipitation we can look at the water use efficiencies of our winter wheat.
If we use the same 5.2 inches for vegetative growth and take that off the 13.05 inches received it leaves us with 7.85 inches for grain production. If we take the 7.85 inches times the 4.7 bushels of production per inch of precipitation we could expect 36.9 bushels of winter wheat per acre. Our yields were 43-51 bushels per acre or slightly higher than what the water use efficiency research data would indicate. If we use the same 5.2 inches for vegetative growth our winter wheat water use efficiency would be 5.5 bushels of grain per inch of precipitation for the 43 bushel wheat and 6.5 bushels of grain per inch of precipitation for the 51 bushel/acre wheat yield.
I would suspect that some of our higher water use efficiencies for the winter wheat may be that we had additional water stored in the deeper soil profile that the field peas the following year weren’t able to utilize. Another possibility could have to do with the crop rotation with the winter wheat following the field peas. This rotation which includes a legume may alter the soil microbe population and diversity and have a positive effect on the winter wheat yields. We may have good water infiltration and water holding capacities due to our long term no till which may give us higher water use efficiencies.
There could be other explanations as well that I haven’t thought of but in any event I have experienced good winter wheat yields following field peas in our continuous no till crop rotation. These winter wheat yields that we had this year also show what an important crop winter wheat is to producers in our area. Winter wheat has an amazing ability to produce a good crop in less than ideal growing conditions.
I’d also like to comment on our “poor man’s cover crop” experiment that we had last year. As you may recall we had two fields of field peas that were lost to hail damage last year. We decided to let the fields grow back to weeds and any field peas that recovered from the hail rather than chemical fallow the ground right after the hail storm. We felt it was more important to get the ground shaded with residue than it was to have a clean field which often results in a soil that is hard to plant a crop into after being hardened by the sun and soil moisture evaporation losses near the surface.
The results of this farm trial were interesting. Our poorest wheat field was one of these fields with a 43 bushel per acre yield. Our best field of wheat was the other cover crop field with a 51 bushel per acre yield. The difference in these two fields was the amount of precipitation we received during the growing season. I don’t think letting the cover crop grow had a detrimental effect on yield. As we usually see in crop production in our region the amount of moisture each field received determined the final yield potential.
Next week I’ll take a look at our field pea yields and how their water use efficiencies compare to the winter wheat in their ability to produce a crop in a below normal rainfall year like we experienced this growing season.