As of April 19, the Nebraska Drought Monitor shows that 96% of Nebraska is experiencing moderate to extreme drought. With planting being essential for everything that happens during the growing season, the dry conditions have led to a variety of issues this planting season. In this article, educators at the University of Nebraska work through the questions they received.

Ground condition

This is perhaps the most critical element of planting, as soil conditions set the stage for the decisions we make regarding planter adjustments, what crop is planted, and planting depth. The dry and open winter allowed the freezing/thawing and the softening of the soils. Some shared that they were seeing the best no-till conditions they had seen in a long time. Others share the high winds blowing away corn and soybean residue – even under no-till conditions – have made the top few inches of soil very hard. When planting in drier conditions, increased down pressure is likely needed; however, be careful not to cause sidewall compaction. Pioneer Hi-Bred Field Agronomist John Mick shares some great planter setting tips alongside other planting tips in his newsletter this week.

Soil moisture and planting depth

Corn must absorb 35% of its weight in moisture to complete the imbibition (water absorption) phase of germination. When adequate soil moisture is available, this usually occurs within 48 hours. Soybeans must absorb 50% of their weight in moisture to complete the soaking process. When adequate soil moisture is available, recent research has shown that imbibition can occur anywhere from eight to 24 hours. Once imbibition has occurred, soybeans enter an osmotic phase and are quite tolerant of soil temperatures as low as 35-40°F, although one would expect that prolonged low soil temperatures lengthen the period from germination to emergence. You can see soil temperatures on CropWatch. Also be aware that soil moisture can help buffer soil temperatures, reducing larger fluctuations.

How does soil moisture affect planting depth? Research has consistently shown the need to plant corn at least 1.5 to 2 inches deep. UNL showed that the best soybean yields were obtained when planting at a depth of 1.75 inches. So the short answer – aiming for close to two inches is a good consideration for corn and soybeans. Planting closer than 1.5 inches leads to more impacts on corn root development, such as rootless corn syndrome. The main concern with shallow soybean planting this year is the potential for PPO herbicide damage, which is mentioned later in this article.

Uniform emergence is more important for corn than for soybeans. For this reason, Rob Nielsen, Emeritus Extension Agronomist at Purdue shares, “When seedbed conditions are dry, be sure to choose a seeding depth that provides uniformly adequate soil moisture for germination and emergence ( corn). Although a seeding depth of 1.5 to 2 inches is a good choice for many conditions, feel free to increase the seeding depth to 2.5 or 3 inches if that is the depth where the plant is. uniform soil moisture. we do not recommend planting much deeper than 2.5 inches.

IRRIGATION CONSIDERATIONS

Irrigate before planting crops:

In general, we only suggest watering before planting if the planter needs a higher soil moisture level to perform well. So if the ground is too hard, too powdery or cloddy, it may be worth rotating the swivel. Another situation to consider before watering is if more than 180 lbs/acre of anhydrous ammonia has been applied in a band with less than 2 inches of moisture received since application to help reduce ammonia burn on the corn. Otherwise, our recommendation is to run the pivot after planting if necessary.

Irrigation Considerations at the Beginning of the Year:

Running center pivots at the start of the season have additional challenges. The first that comes to mind this year are cold nights. The usual recommendation is not to run a pivot when temperatures are below 40 degrees. This year several pivots have operated below 40 degrees without issue, but keep in mind that with low dew points the pivot can ice up when the actual air temperature is well above 32. So, if you choose to run in these conditions, keep a close eye out for ice buildup.

Second, bare, dusty soils this spring will very easily seal against rain or irrigation, so keep an eye out for runoff issues, even with fairly low application amounts. And third, make sure if you irrigate that you put in enough to bring the water down to the moist soil below. This is especially a problem with tillage or where fertilizer knives have been used and have dried out the soil.

Irrigation for herbicide activation:

It is important that herbicides are activated with 0.5 to 0.75 inches of rainfall or irrigation, preferably five to seven days after herbicide application. If the moisture received is less than this amount, some herbicide products can stay on the ground for up to 14 days without being fully activated. We will have to see how high winds blowing through the soil and blowing away soil particles containing herbicides will impact future weed control.

Irrigate to reduce urea loss:

For those who have applied dry or liquid urea to the soil surface, especially without using an inhibitor, a 0.5 inch irrigation can help incorporate the urea into the soil and minimize soil loss. urea. If irrigation is not available, no inhibitor has been used, and no rain has been received within seven days, monitor the maize crop to determine if nitrogen deficiency is occurring due to from a loss of nitrogen. Losses can occur early and be significant if there are high surface crop residues, high soil temperature (>70°F), wet soil, high soil pH (>7.0) or sandier soils, while losses may be lower with dry soil, cooler soil temperature (

Strip-till irrigation:

Regardless of whether the anhydrous was applied in the fall or spring, and regardless of the amount applied, ammonia burn is likely this year in strip tillage situations due to dry conditions. Sometimes ammonia burn is seen early with germination and seed emergence. Most often it is seen when the roots grow four to eight inches long and hit the ammonia band. Irrigation can help lessen the effects of ammonia damage.

Impacts of irrigation and cold water:

John Mick shared that the water from irrigation wells in the southern part of the state is often around 50-53°F, with a slightly lower temperature as one moves north in the state. ‘State. These temperatures are not an issue to consider when it comes to negative impacts on water-soaking seeds.

HERBICIDE CONSIDERATIONS

PPO inhibitors are an effective chemistry often used for pre-emergence application in soybeans. The various PPO inhibitor active ingredients, products and time restrictions can be reviewed in this article. Injury to soybeans may occur in situations where the seed/germinating seed comes in contact with the PPO inhibitor herbicide and by splashing water on the hypocotyl and cotyledons of the emerged soybean.

Here are some considerations for reducing soy damage:

• DO NOT apply a PPO inhibitor herbicide if the seed vee is not closed, if the soil is cracking along the seeding trench, or if soybeans are beginning to emerge/emerge. Another option if there is concern about PPO inhibitor damage is to consider a Group 15 herbicide (such as acetochlor, pyroxasulfone, etc.) as a residual in a postemergence application. once the soybeans have emerged. Remember that residual herbicides applied post-emergent have no foliar activity, so they will not control emerged weeds but will prevent the emergence of new weeds.

• Do not plant soybeans shallow (less than 1.5 inches), especially if the soil at the seeding depth is dry. If a PPO inhibitor is applied under these conditions, it may allow soybeans to soak up water containing the herbicide, particularly if a rain and/or irrigation event occurs after application.

• If the soybeans are planted in moisture to allow the soak phase to complete, the herbicide can be applied within a few days and watered in as long as the seed vee is closed and no cracking of the trench soil does not occur.