Regional Crop Update: August 26 - September 1, 2020

September 2, 2020 10:29 PM
Blog Post

Drought continues to expand across the state, and August 2020 came in as one of the driest Augusts since 1893 across the state. Crops appear to be racing toward maturity, with several reports of both corn and soybean very near harvest-ready. While many farmers are approaching harvest quickly, other farmers are evaluating options for derecho-damaged acres that will not be harvested; see our Storm Damage Resources page for more information on managing downed corn, grazing considerations, and other helpful links. Other issues noted by field agronomists include a decline in corn stalk quality, tar spot, ear rots getting an earnest start, and forage concerns. Read on for more specifics for what’s happening in different regions across the state.

Iowa August 2020 rainfall ranking
The southeastern portion of the state experienced the driest August in 128 years. Source:

Northwest Iowa

Joel DeJong (Region 1): “Many acres of soybeans began to yellow with the heat of the last week. Some cornfields really shut down, many fields have areas that have finished the fight, most have browning husks. Yet, neighborhoods that received rainfall still look to have quite good yields. Variations between and within many fields will be extremely wide this year. Most of the silage harvest is complete, and was getting a little dry by the time it was completed.  Spoke at a couple of field days within the last week where root pits were dug to discuss soil characteristics and to look at how deep roots could be found in the loess soils of NW Iowa. The first Sioux County site had some roots at the bottom of the pit – about 7.5 feet deep. The other site in Woodbury County dug a really deep pit, and the lowest root hair found measured nearly ten feet below the surface, with many root hairs found greater than nine feet deep. This site needed it, because the first seven feet were very dry. We have only gotten by with the use of subsoil moisture this year – I hope we can start recharging for next year soon."

Paul Kassel (Region 2): “Corn and soybean crops have continued their rapid pace of maturity. Most of the corn fields have turned a mature brown color. Some of the corn fields – even on fields with good soil - have begun to reach the black layer stage of development. Other corn fields – also on good soil – have retained some green color and have reached the half milk line stage of development. Soybean fields have reached late R6/full bean stage to early R7/beginning maturity stage. Soil differences are very apparent in area fields as soybean plants are retaining more green color in lower parts of the landscape. The counties in my area run the gamut on the US Drought Monitor. Parts of Sac county are in D3/extreme drought and most of Winnebago has no drought designation at all. Most of the rest of the area is D1/moderate drought or D3/severe drought."

corn ears at R5.5
These corn ears have reached the R5.5 (half milk line) stage of development. Photo by Paul Kassel.

North Central Iowa

Angie Rieck-Hinz (Region 3): “Dry conditions persist, although we have had widely scattered showers in some locations. As an example, from April 1- to September 2, Clarion is 8.69 inches behind average rainfall, Humboldt is 9.85 inches behind, and Rockwell City is 10.05 inches behind average. However, Northwood is right on average for rainfall during this time frame of 21.19 inches (Iowa Mesonet). Dry conditions have pushed maturity. There is some black-layered corn out there and in some places moisture content is already down to 20%, but most corn is at three-quarters milk-line. Even corn with green leaves is experiencing browning husks and drooping ears. Farmers should be prioritizing corn fields for harvest as stalk quality is deteriorating quickly in dry areas. Many soybeans are R7. Just a reminder, make sure you have a fire extinguisher (or two) in good working condition, on the combine and in the tractor and truck!"

Central Iowa

Meaghan Anderson (Region 7): “Rainfall in the last week totaled mostly under 0.1 inch, with some pockets receiving more rainfall, but dry conditions overall continue to persist and spread further east. Many central Iowa fields quickly went downhill in health and appearance after the derecho, but the heat last week really sped things along toward maturity. Some corn fields deemed "mechanically unharvestable" have been tilled or managed to reduce residue size already, and I expect more will be to follow in the coming weeks. Most fields are in the late R5 stage and some have reached physiological maturity already. Some farmers are reporting hand checks in corn in the mid-20s for moisture already, meaning harvest is just around the corner. Tar spot is easier to find in fields now than it was earlier in the season. Ear rots are getting a start in some corn damaged by derecho; fusarium is the most common one I've seen on ears. Any corn that will be harvested should be prioritized for harvest based on maturity/moisture and other issues like stalk rots or ear rots. Soybean fields are R6-R7 still, with more fields turning color every day. Some fields are showing apparent unevenness in the soybean canopy, likely due to plants lodging over after the derecho event; I expect to see more of this as we approach soybean harvest, especially if we get rainfall or wind. Cover crop seeding has started in some areas. As harvest approaches, keep in mind that we have several hazards to face this year: very dry conditions, high likelihood of plugging up equipment, and possibility of debris in fields. Please be safe out there!"

Soybeans changing color
Soybeans are changing color quickly. Photo by Meaghan Anderson.

East Central, Southeast, and South Central:

Virgil Schmitt (Region 9): “Rainfall last week in the counties I cover was generally less than 0.5 inch. In general, temperatures last two week in the counties I cover were four or more degrees above normal. Most corn fields are at R5.5 +/- and generally looking good, except for storm damaged fields. The heat of last week, combined with lack of rainfall, caused plants even on loam and finer textured soils to start showing drought stress. Occasional sightings of tar spot continue. Soybeans are mostly R6. In general, they also look good. Cover crops and dealing with derecho-related issues were common topics of discussion last week.

Temperature departure for late August

Josh Michel (Region 11): “For most of the region, it’s been three weeks since any measureable rainfall. Depleting soil moisture and above average temperatures have greatly increased the amount of heat stress crops are displaying. In many areas, grain fill and early maturing are being pushed along ahead of schedule. Corn fields are generally at R5, with many around half milk line. Many fields are firing up to the ear leaf, with several having turned completely brown. Harvesting for silage continues in many areas, and I expect combining to start in a few isolated areas within the next week. Soybean fields are generally around R6, with a few fields reaching R7 later this week. Almost all soybean fields are showing signs of some heat stress. Soybeans on lighter and poorer soils are showing severe stress, causing many to mature very quickly and begin to drop leaves. The majority of soybean related calls consist of minor insect feeding and increasing reports of spider mites. As expected, alfalfa fields and pastures continue to grow very slowly. Some pastures remain dormant. There is an increasing concern regarding forage supplies as conditions deteriorate. I continue to receive calls asking about fall seeding and testing cover crop seed.”

pasture conditions have deteriorated
Pasture conditions have deteriorated in southeast and south central Iowa. Photo by Josh Michel.

Check out the map below to find your local ISU Extension field agronomist and find their contact information here!

Field agronomist location map


Meaghan Anderson Field Agronomist in Central Iowa

Meaghan Anderson is a field agronomist in central Iowa and an extension field specialist at Iowa State University Extension and Outreach. Educational programming is available for farmers, agribusinesses, pesticide applicators, certified crop advisors, and other individuals interested in...

Rebecca Vittetoe Field Agronomist in EC Iowa

Rebecca Vittetoe is an extension field agronomist in east central Iowa. Educational programs are available for farmers, agribusiness, pesticide applicators, and certified crop advisors.

Areas of expertise include agronomy, field crop production and management of corn, soybeans, and...