KANSAS CITY — Concerns about late planting of fall row crops, including corn, soybeans and sugar beets, as well as spring wheat, have been building as wintry weather has persisted across the key Corn Belt and Upper Midwest states well into spring. But it appears the weather may have turned warmer just in time to allow farmers to get intended acres planted.

The U.S. Department of Agriculture in its weekly Crop Progress report released April 23 said spring wheat was only 3% planted in the six largest-producing states as of April 22, compared with 21% at the same time last year and 25% as the 2013-17 average for the date. But no spring wheat yet was planted in the key states of North Dakota (13% average for the date), Montana (24%) or Minnesota (25%), with only 2% planted in South Dakota (50%). Those four states were expected to account for 91% of planted area for spring wheat other than durum this year.

Barley planting in the five largest states was 11% completed as of April 22, compared with 33% as the average for the date, with none of the crop yet planted in Montana (34% as average for the date), North Dakota (9%) or Minnesota (17%).

Across the Upper Midwest, sugar beet planting had yet to begin in the two largest producing Red River Valley states of Minnesota (34% as the average for the date) and North Dakota (28% average), with Michigan only 1% planted (15% average).

But most of the trade is focused on corn, which along with soybeans account for about 56% of total principal field crop planted area in the United States. The U.S.D.A. in its March 29 Prospective Plantings report said farmers indicated they intend to plant 88,026,000 acres of corn and 88,982,000 acres of soybeans in 2018.

Corn planted in the 18 major states was 5% completed as of April 22, compared with 15% a year ago and 14% as the 2013-17 average. No corn yet was planted in top-producing Iowa (11% as the average) or Minnesota (13% average), with 4% in Illinois (20%), 1% in Indiana (5%) and 2% in Nebraska (9%), the top five states.

Soybeans in the 18 major states were 2% planted as of April 22, even with the five-year average and not of as great a concern as corn.

Weather prospects looked better last week for a window that would allow farmers to plant a significant amount of fall crops, although Upper Midwest spring wheat and sugar beet areas still were mostly too cold. In the central Corn Belt, soil temperatures were nearing the necessary 50 degree mark and little if any rain (or snow) was in the forecast.

Analysis done by Scott Irwin and Todd Hubbs in the Department of Agricultural and Consumer Economics at the University of Illinois suggests a minimum of 14 “suitable” days are needed to plant the entire U.S. corn crop. They studied planting progress from 1980 through 2017 in Iowa, Illinois and Indiana, which account for 35% of U.S. corn acreage and were seen as representative of states across the Corn Belt.

While massive amounts (as in millions of acres) of land can be planted daily, the study dispelled “conventional wisdom” that suggested the U.S. corn crop could be planted in as few as five days as the result of technological advances such as GPS auto-steer systems and huge equipment.

The University of Illinois study indicated, surprisingly, that maximum acreage planted per day had declined the past two years. The authors suggested there may have been more focus on planting soybeans earlier, or that equipment wasn’t being fully utilized.

Corn planting dates also seemingly have been getting earlier in recent years. Data from DuPont Pioneer suggests planting in early April has been optimal for the central Corn Belt (which includes Iowa, Illinois, Indiana) and early May in the northern Corn Belt. After those dates pollination is pushed into the hotter days of summer and yields begin to decline.

The optimal corn planting period has passed for the central Corn Belt and is fast approaching for northern areas. There is no doubt most of the intended acreage will be planted, but it seems likely that yields may be trimmed and some acres may be switched to soybeans if enough corn planting progress doesn’t occur in a week or two.