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Extension Educator Urges Producers to be Mindful of Drought Impact on Various Crops

by Wyoming Livestock Roundup

This past winter and the start of spring have been dry and windy. Current forecasts, as of April 20, for snowpack and potential runoff are between 75 percent to 99 percent across the state, with the exceptions of the Laramie River watershed which is at 104 percent and the Cheyenne River watershed, which is at 67 percent. 

This dry pattern can also be seen in Wyoming’s drought monitor report, which indicates every part of Wyoming is in some level of dry or drought condition. It goes without saying, these dry conditions will most likely have an impact on Wyoming’s agriculture. Currently, attention is focused on potential irrigation levels for the season.  

Throughout this year, producers will need to watch out for drought impacts on crops in their operations.

Producers should report any potential losses to Farm Service Agency (FSA) and crop insurance companies at the first indication of yield loss due to weather related events.

High nitrate levels
in forages

Everyone knows drought conditions tend to produce lower yields in native and cultivated forages, especially non-irrigated forage production dependent on precipitation. 

Drought conditions also increase the risk of toxic plants, especially in situations when toxic plants are the only thing green in a pasture. 

Similar to toxic plants, drought stress on forages can induce high nitrate levels which can result in toxic levels in livestock. This is typically thought of as being an issue in drought stressed oats. 

However, it’s actually a problem in all small grain  forages such as oats, wheat, barley, corn, etc. High nitrates can also be found in other types of crops, weeds and fertilized pastures grazed during the growing season. 

Managing alfalfa 

Nitrates are not a concern with alfalfa; however, under dry conditions alfalfa can produce higher crude protein levels and digestible matter, which can lead to an increase in bloat potential in situations where livestock directly graze alfalfa or eat green chopped alfalfa. 

The best drought management techniques for alfalfa include harvest timing, irrigation and insect control. To maintain a healthy stand of alfalfa harvests, plants need to be managed appropriately to maintain root vigor and health. This is accomplished by properly timing harvests and maintaining good above-ground growth. 

Harvest timings are usually based on the percent of bloom. Producers should be aware drought stressed alfalfa can bloom earlier than normal, while plants are still short. This puts root reserves at risk because they have not had appropriate time to recover from the previous harvest. Alfalfa stands should be left uncut if they do not exceed 15 inches in height.  

If irrigation is limited, try to maintain alfalfa fields based on water needs. It is critical to get water back on the field as soon as possible after harvest. A maximum of 10 to 15 days after cutting is ideal. 

The last drought management strategy is insect control. Drought conditions can change insect behavior or enhance insect problems.

For example, rangeland insects like grasshoppers move into alfalfa fields in search of food sources. Also, remember to watch for flower-feeding insects, such as blister beetles, especially when alfalfa is cut at high percentages of bloom.  

Drought effects
on corn yields

Corn yields are very susceptible to drought conditions, with yield losses resulting from four consecutive days or more of water stress. Leaf rolling is the primary symptom of drought, with greying of leaf tissue in severe conditions. The greatest water demand for the crop is in the late vegetative stages through the blister stage, though yield loss can occur any time during the crop life cycle. 

The crop development stage dictates the type of loss incurred by drought. For example, stress during the sixth and eighth leaf stages results in fewer kernel rows, but stress at the eighth leaf to 17th leaf stage results in fewer kernels per row.   

Drought stress during pollination ultimately results in poor pollination and fewer kernels per ear. Temperatures greater than 95 degrees Fahrenheit during pollination with low humidity and low soil moisture levels can result in poor pollination because of desiccation of silks and damaged pollen grains. Pollen is killed once temperatures exceed 100 degrees Fahrenheit.

Management depends on remaining yield potential for the year, which should be assessed after pollination occurs. The success of pollination is determined with a shake test directly after pollination or assessing how many kernels are expanding during the blister stage between seven to 10 days after pollination. Manage the field with normal activities if good pollination has taken place.

Producers should consider harvesting poorly pollinated fields for forage or silage.

Wheat developmental

Wheat yields can be impacted during three developmental periods: germination through tillering; jointing through flowering; and grain fill. The first developmental period impacts the number of heads produced, the second period impacts the number of kernels per head, while the third period impacts seed weight. Drought stress during flowering and grain fill results in the most significant yield loss.  

Drought impacts more than yields, it also affects crop diseases, insect pests, fertility programs, tillage, harvest equipment and quality of irrigation water. All these production impacts contribute to the overall economic impact droughts cause to agriculture markets, food availability and consumer prices.  

Current drought conditions are causing low soil moisture levels for spring planting. Possible shortages in irrigation water may impact yields in perennial pastures. 

If feasible, manage irrigation timings and schedules to target critical crop development stages to minimize yield losses caused by drought. Maintain good records which can be used to report any potential losses to the FSA and crop insurance companies at the first indication of yield loss. 

Jeremiah Vardiman is a University of Wyoming Agriculture and Horticulture Extension Educator. He can be reached at

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