Planting delayed for most of Iowa

The crop insurance planting dates have come and gone with barely a field planted for many farmers across Iowa in stark contrast to the last two springs. Cooler temperatures in early April and persistent rainfall has prevented much progress, as indicated by the USDA Crop Progress and Condition Report on April 12. Rainfall totals over four inches in the past two weeks for a good swath of the state from southwest to northeast has replenished soil moisture. Now with a full soil moisture profile, farmers and agronomists are closely watching the weather forecast to see when a planting window will open.

Planting window

The planting window for optimal corn and soybean yields extends from about mid-April to about May 15-20 in Iowa (Figure 1). As we approach the end of ideal planting window, corn yield potential drops faster than soybean yield potential. Prioritize corn planting ahead of soybean as those mid-May dates approach.

While the ideal planting window is very important, planting when soil conditions are fit is equally critical. Soil temperatures should remain warm (>50^oF), and frost chances are minimal at this point in the season with an overall warmer-than-average expected outlook. Soil moisture ranges substantially across the state, so all farmers should pay careful attention to field conditions and equipment settings when it is time to plant.

How fast can we plant?

Iowa farmers can plant an incredible number of acres in a single day. Larger planters, faster planter speeds, and possibly multiple planters per operation have led to this ability. Per suitable day over the last five years, the average number of corn and soybean acres planted peaks at ~950,000 acres per day during week 20 (third week of May; Figure 2). In three of the last 10 years, the peak was 1.6 million acres per day or more. For reference, the Prospective Plantings report indicated 13.1 million acres of corn and 9.9 million acres of soybean expected to be planted this spring. If all planting occurs at its fastest pace, Iowa corn and soybean acres can be planted in just over 14 days.

Breaking out just the corn planting potential over the last decade (Figure 3), farmers have planted up to approximately one million acres per day during weeks 16 to 20 (third week of April through the third week of May). The last year when corn planting had not started by the third week of April was 2022. Greater than 95% yield potential can still be achieved when corn planting occurs before mid-May.

Over the past five years, Iowa soybean farmers have planted 280,000 to 415,000 acres per day during weeks 17 to 21 (last week of April to third week of May; Figure 2). Over the last 10 years, soybean planting has begun during the second week of April (week 15) three times; however, planting has always started before the first week of May (week 18; Figure 4). And during peak soybean planting, it is not uncommon to plant more than 600,000 acres per day. Soybean yield potential remains above 95% yield potential when planting occurs before May 20.

While the weather may continue to add challenges to field preparation and planting, farmers will be ready when the window of opportunity arrives. The short-term forecast for much of the state shows storm chances clearing out on April 17 and providing a period of warm, sunny conditions to dry soils. Prioritize planting into adequate but not excessive soil moisture and carefully monitor planter settings to avoid sidewall compaction.