Lessons from Mother Nature: Frost and weather impact on wheat yields

Dave Pike, Ph.D.
Senior Scientist

Spring 2017 was challenging for winter wheat growers from Texas to North Dakota. Cold weather during head development led to stand loss and injured plants. Crop condition reports from these states read like a litany of things that can go wrong; snow in Southwest Kansas was so wet and heavy that wheat stems broke under the pressure. Recurring freezing temperatures and winds from Northern Oklahoma to Nebraska damaged cell processes and caused plant dehydration, from which recovery may not have been possible. Flooding from persistent rains in some low spots created anaerobic conditions for root systems and resulted in plant death. Re-freezing of some flooded areas produced surface ice, resulting in the entrapment of gases and toxic conditions for root development.  
Taking all the various factors into account, predicting wheat yields is a challenge this season. Topography and production practices will dictate that not all fields, and not all areas in a field, will have been equally affected. North-facing slopes tend to be exposed more prominently to damage from freezing winds. Low areas in a field that have accumulated snow and have flooded readily are less likely to recover. Late planted and later maturing varieties may have escaped much of the damage, as will some of the varieties, which are more winter-hardy. Varieties heading at the time of repeated freeze-thaw episodes could be expected to be hit hard.

Although the whole story cannot be told by a single image, Agrible scientists have assembled the following map as an example of the data we use to calculate areas most affected by a freeze. Agrible uses this information, along with similar maps from subsequent freeze events, snow deposition, and precipitation, to estimate the potential risk of freeze/frost and weather on winter wheat yields.

(This map reflects the freeze occurring on the 23rd of April of this year, with darker shading corresponding to a longer freeze duration.) 

(This map reflects the freeze occurring on the 23rd of April of this year, with darker shading corresponding to a longer freeze duration.) 

Within Morning Farm Report, risk levels are represented graphically by cards showing an approximate range of yields that could have resulted from freezing weather—as shown in the figure below showing minor, moderate, and significant injury potential.

For Morning Farm Report users, data input on wheat variety, planting date and field location, and production practices are all factored into the wheat yield estimates from the date of planting and on through harvest. Morning Farm Report’s daily emails keep users informed of the advancing crop stage, as well as alerts and advisories to direct the user’s attention to critical crop needs.