How Do We Prepare for the 2022 Growing Season?

U.S. Drought Monitor map released April 7, 2022.

There is a lot of concern among farmers about dry spring conditions as we head into the 2022 growing season. Significant areas of the western U.S. are encountering extreme to exceptional drought. In the Midwest, the southern tiers of Wisconsin counties and the northern 1-2 tiers of Illinois counties are abnormally dry or under moderate drought.

Figure 1 describes the 30 yr monthly average precipitation at the UW Agricultural Research Station in Arlington. Only 23.5 inches of precipitation was measured during 2021 compared to the 30-yr annual average of 35.2 inches. We  typically get most of our precipitation during April, May and June. The variability (risk) of precipitation patterns during April to June is quite high ranging from 3.8 to 5.4 inches (standard deviation= + 1.9 to 2.7 inches). Monthly precipitation amounts can range from 1.8 to 7.9 inches of precipitation during April, May and June.

Figure 1. Monthly precipitation at the UW-ARS in Arlington. Data were derived from the Midwest Regional Climatological Center. Error bars are the standard deviation of the 30 yr monthly average.

During 2021, monthly precipitation was outside of the error bars in Figure 1 only during April and November. Drier conditions during April allowed for early planting, while drier grain moisture was observed at harvest. The month that was average for precipitation was August which is the grain-filling period for corn. No 2021 precipitation monthly average was above the 30 yr monthly average. So even though precipitation was one of the lowest on record, the distribution was adequate for near-record  grain yields.

Some of the current drought conditions described by the U.S. Drought Monitor for Wisconsin and Illinois are a holdover from the 2021 season. Since January 2022, the amount of precipitation  measured at Arlington is average. Soil profile water content is likely lower than normal. 

How Do We Prepare for the 2022 Growing Season?

The short answer is that you “manage for the average.” Don’t change things too much unless you have been considering and preparing changes in your management style for some time. The weather during 2022 could be cooler/warmer and/or drier/wetter than normal.

Again, I would “manage for the average” during 2022. No one can predict the weather. If you are convinced that the weather is going to be drier than normal, then I would consider the following:

  1. Select a hybrid that is bio-engineered to include drought “tolerant” transgenes. Be wary of hybrids traditionally bred for drought “resistant” traits.
  2. Use hybrids with the Bt-ECB bio-engineered trait. Stalk integrity will be important for water molecule movement within the plant and will likely increase standability at harvest. Often mycotoxin issues are more often observed in drought stressed years because of increased corn borer activity.
  3. Select a hybrid that is shorter-season than typical for your field. You will give up yield compared to a full-season hybrid, but the the shorter-season hybrid will go through pollination earlier when soil profile water might be adequate to ensure pollination.
  4. Plant early. Planting corn early has the same effect as  selecting a shorter-season hybrid. Plants will go through the pollination phase earlier when soil profile water content is greater.
  5. Lower plant population. Our data shows that grain yield is not affected by plant population during a drought year. By lowering your plant population you capture some return on investment by lowering seed cost.
  6. Rotate your crops. Rotated corn grain yield during a drought year is increased (25 to 30%) more than continuous corn. 
  7. Use no-tillage. Residue on the soil surface acts as a mulch and a boundary layer for evaporation from the soil surface.
  8. Control weeds. Weeds will compete with corn for water resources.
  9. Do not over-apply nitrogen. Apply at MRTN rates. Nitrogen increases corn leaf area thereby increasing the potential amount of surface area and cooling load that the plant requires for transpiration.

Some of these management decision changes have the potential to leave yield in the field during a normal weather year. As we saw during 2021, some of these decisions are about timing of precipitation events. I remember the 2005 and 2012 when weather conditions were dry through mid-July. Adequate rains came in mid-July and soils that had higher soil water content allowed plants to escape drought effects on pollination. For some, early planting date and shorter-season hybrids did not work and fields were abandoned.

Joe Lauer
University of Wisconsin

The Magic of Corn Seed Germination and Emergence

I think nearly every corn planter in Wisconsin was planting this past week. There are some wet areas in northeastern Wisconsin that have prevented planting, but a significant jump in planted acreage should be measured by USDA-NASS in next Monday’s progress report.

Now the magic begins when dry seed imbibes water and bare or brown fields turn greener every day across the landscape. The germination process and the success of the seed in emerging and establishing is key and the first yield component determined for the growing season.

Protected within the seed coat is an embryonic plant that remains dormant until germination is initiated by the physical process of imbibing water. The white starchy endosperm is the main energy source until the young seedling is established. After planting, water and oxygen are imbibed into the seed for 24-48 hours activating the growth hormones and enzymes. Starch is broken down supplying the embryo with energy for metabolism and cell division.

Within the embryo is a miniature corn plant that already has a primary shoot, leaves and root system protected by rigid sheaths called the coleoptile (above-ground) and coleorhiza (below-ground). The first structure to emerge from the seed is the radicle root, followed by the coleoptile and seminal roots.

Figure 1. Diagram of germinating corn. Photo and graphic by Mimi Broeske.

The coleoptile is pushed to the soil surface by the mesocotyl. When sunlight falls on the coleoptile tip, enzymes are activated that soften the tip allowing the first true leaf of the plant to break through. The growing point of corn is 3/4 of an inch below the soil surface and will remain below-ground until the plant has 5 to 6 leaves.

The germination process from dry seed to seedling emergence requires about 125 Growing Degree Units (GDUs). Normally in the beginning of May, we accumulate about 10 GDUs per day, so emergence takes about 12 to 13 days. The 2022 growing season is starting out fast with record high temperatures, and I have seen some recently planted fields already emerged. Emergence GDUs may need to be adjusted:

  1. If conservation tillage is implemented, add 30-60 GDUs.
  2. If planting date is before April 25, add 10-25 GDUs.
  3. If planting date is after May 15, subtract 50-70 GDUs
  4. If seeding depth is below 2 inches, add 15 GDUs for each inch below.
  5. If seed-bed condition has soil crusting or massive clods, add 30 GDUs.
  6. If seed-zone soil moisture is below optimum, add 30 GDUs.

There might be many reasons why a seedling does not emerge in a stand of corn. The germination process is really a race between pest pressure (diseases and insects) and the ability of the seedling to outgrow the pest. Seed treatments protect the seedling from disease and insects for the first 30 to 45 days of the growing season. Planting into cloddy/crusted or cold soils can result in seedling leaves unfurling below-ground, reducing plant stand and yield potential. Imbibitional chilling can result in plant death.

This one of my favorite times of the year in Wisconsin. I wonder what the growing season has in store for these developing plants. As you drive around the state, enjoy the landscape and all the different greens that develop over the month of May.

Corn Imbibitional Chilling: Fact or Fiction

For the first 24-48 hours after dry corn seed is planted into the ground, all that takes place is physical imbibition of water into the seed. Water and oxygen move slowly into the kernel through the seed pericarp. Membranes re-hydrate and hormones and enzymes are activated. After the seed swells, enzymes begin to breakdown starch in the endosperm. Sugars supply the embryo with energy for metabolism and cell division.

Imbibitional chilling occurs when membrane re-hydration is disrupted by free radicals before the seed finishes swelling. Cold water is much more disruptive than warm water. Sugars and salts leak from the cells and kernel providing a food source for pathogens and other microbes. It becomes a race for the plant to emerge or death from pathogens.

One of the most dramatic examples of imbibitional chilling occurs with sweet corn. In a study conducted by Bill Tracy (2005), untreated seed of six supersweet corn varieties were exposed to three treatments. Each treatment consisted of one 24-hr period at 40° F temperature and five days at 75° F. Seed was placed in rag dolls with no soil.

Sweet corn seed has a wrinkly seed pericarp with numerous cracks, fissures and potential endosperm leakage sites. In this study, most seed death occurred within the first 24-hrs (day 1) of being exposed to 40° F. Significant variety differences for the amount of seed death were observed. Significantly less seed death was occurring when exposed to 40° F on days 2 and 3, and no seed death when exposed to 40° F on day 4.

Figure 1. Six supersweet corn varieties exposed to one 24 h period at 40° F and five days at 75° F.

One current recommendation is to begin planting corn when soil temperatures are in the high 40s and the short-term forecast calls for warm days that will continue pushing soil temperatures higher. If soil temperatures are in the high 40s and the weather forecast calls for cold wet conditions within the next 48 hours, soil temperatures will likely drop and planting should be delayed until temperatures warm.

That recommendation is simply not our experience in Wisconsin and likely the northern tier of U.S. states. If we waited until soil temperatures were above 40° F we would need to wait until May in many years (Figure 2). It only gets later as we move north. Yet, our highest yielding planting date are in late April and early May.

Figure 2. Last date when the minimum soil temperature at the two-inch depth was above 40° F at Arlington, WI.

The only time I thought our UW Corn Hybrid Trial plots had been affected by imbibitional chilling was during 2006 at Seymour, WI (Figure 3). I happened to be along on that planting trip. It began to snow after we had finished planting and continued to be cool and wet for the next 72 hrs. We went back to the field a few weeks later and unbeknownst to us at planting, found that the field had shallow swales and a drainfield. Corn emergence was perfect over the drainfield and on the ridges of the swales. However, much plant death occurred between the drainfield spurs and swale depressions. We did not observe standing water, although it could have been another possible reason for plant death. We abandoned the trial due to stand variability.

Figure 3. Daily air temperature and precipitation at during 2006 at Seymour, WI. The red arrow indicates when the UW hybrid trial plots were planted.

Our current recommendation for beginning to plant corn seed is, “In southern Wisconsin, plant corn anytime after April 20, if the field is ‘fit’, and after April 30 in northern Wisconsin.” If the short-term forecast is for cold temperatures and snow/rain, then the prudent thing to do is hold-off planting. We have available excellent seed treatments that can protect the seed for the first 30 to 45 days after planting.

This advice we use to plant and establish the UW hybrid trials at 14 locations around the state. We have often had snow on our plots with no establishment and emergence issues. For the last 5 years we have planted a few hundred feet of four hybrids beginning in March and then every 2-3 weeks – we do this to get the planters out and tuned. We do see hybrid differences and in only one case did we see emergence issues for all four hybrids. Remember that insurance coverage does not begin until planting dates after April 10.