What Does This Flash Drought Mean for Our Crops?

 By Will Fulwider

While we are seeing a little bit of rain throughout much of the eastern half of the state, the national drought monitor updated southern Wisconsin to D1 last Thursday, putting it in the moderate drought category. How did we get here, to suddenly experiencing a ‘flash drought’? I say suddenly because Wisconsin just experienced the wettest winter on record before rolling into the fourth driest May on record. The long and short of it is that a high-pressure dome has parked itself over Canada driving out moisture and bringing generally sunny skies–unless the resulting winds drag along Canadian wildfire smoke like last week. While the forecast is that this dome will break apart by the end of this week, where should your level of concern be for this year’s crop growing season? 

Soil moisture, corn, and soybeans

Generally, we are in okay shape. Most farmers had good soil moisture for planting both corn and soybeans, with the week ending on May 30 showing adequate soil moisture for 53% of the topsoil in the state, with 90% of the corn and 82% of the soybeans already planted. Beyond the initial imbibition of water and subsequent germination, corn and soybeans do not require much water in these early vegetative stages, and moderate drought stress does not have a huge impact on yield if the crops can make it to emergence. The saturated soils we had at the beginning of May have led to fairly normal soil moisture levels down to 3 feet, while the upper eight inches are in the 10-20 percentile of historical records, i.e., much drier than average. Our growing crops’ roots will chase that water down into the deeper levels of the soil. And, importantly, our soils still had moderate soil moisture during the summer’s first heatwave at the end of May. Temperature is a greater stressor to young crops than moisture. As temperatures climb past 90°F, evapotranspiration rates rapidly increase, crop growth slows, and the roots struggle to dig deeper for trapped moisture. Thankfully, the heat has quit for a bit and we can a little more calmly pray for more rain. While the lack of rain is concerning, now is not the time to panic; the most critical time for adequate soil moisture for corn is late vegetative to silking and pod filling in soybeans. 

What about wheat? 

While winter wheat water use peaks right about now and in the weeks ahead during grain filling, dry weather is not as worrisome and can actually be helpful. Having lived through the Wisconsin winter, wheat is a tough crop with roots that can go down almost 7 feet. As I said before, even though our topsoils are abnormally dry, our subsoils are well within normal soil moisture. Why are dry conditions helpful for growing wheat in Wisconsin? Dry conditions lead to lower and more uniform grain moisture at harvest time, speeding up harvest and allowing farmers to forgo additional post-harvest drying down to the magical 13.5% moisture content. Furthermore, some of the biggest economic risks for wheat in Wisconsin, Fusarium Head Blight or scab and lodging, are far less likely in dry conditions, and disease incidence in the state is very low. 

Hay and forage

The dry weather in late May made for easy haymaking, and many farmers put up a fine first crop and are so far hopeful for the second. Our early season soil moisture promoted good root growth on alfalfa stands. Perennial crops such as alfalfa or pasture grasses have much deeper root systems (in good soil, alfalfa roots can reach down beyond 20 feet!) than our annual crops and can therefore take advantage of the moisture deeper in our soils. Dry and hot conditions along with inadequate soil moisture following a cutting can reduce the number of stems produced, the length between nodes, and accelerate date to flowering. Continued dry conditions coupled with lower yields may tighten hay stocks, but the state has seen a rising interest in alternative forages, such as sorghum-sudangrass and fall oats, or winter cereals harvested for forage that might help to keep bunkers and silos full. Some of these alternative forages like sorghum-sudangrass or millet are well-suited to later plantings and dry/droughty conditions, providing emergency forage with good tonnage when we see early crop failures or poor emergence. 

Sidedressin’ time

If there is an ideal time to experience drought conditions during the summer time in Wisconsin, it might be now: water needs are relatively low for most of our crops and first crop hay making was able to proceed at an almost leisurely pace. While the crops might be in okay shape, they will soon require the fertility that we have been delaying. Granular urea depends on rains to incorporate nitrogen and ensure it is not lost to ammonia volatilization. Even those using UAN need still be careful as it is still 50% urea, making it prone to ammonia volatilization during hot and dry conditions as well. Delaying until it rains, like today, incorporating, or knifing it in are all options during these conditions. Farms might also consider the use of a urease inhibitor, nitrification inhibitor, or polymer coated N product if applying nitrogen before it has reached V6 stage. While these products cannot guarantee a benefit because of our inability to predict what conditions will be like after applying nitrogen, they can operate as an “insurance” against conditions that remain favorable to nitrogen loss by slowing the breakdown of nitrogen into losable forms.