Counting crops with USDA
Though USDA's October Crop Production report is typically only considered a starting point or trigger for a lot of market activity, it's also the culmination of a lot of work around corn and soybean country. Late last month, USDA-NASS staff let me tag along while they took ear and pod counts for the upcoming report.
Greg Thessen, state director of the NASS Iowa field office, and Doug Darling, Mitchellville, Iowa, rancher and retired USDA specialist, headed to a field in central Iowa Thursday, September 29, to collect data for the October 12 report. Iowa enumerators gather data from 290 corn fields and 210 soybean fields.
The field data collection process for USDA's reports is randomized. Enumerators like Darling are given specific instructions on field locations, down to the number of paces and rows. "They're given specific counts, and specific tools to get those counts to make it objective so they can't let their own subjectivity enter into the data that they're collecting," Thessen says.
During the late-September corn counts, enumerators gather data on 2 15-foot-long adjacent rows. In this field, Darling was required to walk exactly 430 paces in from the field's edge. After counting ears, he harvested 1 of the 2 rows examined, and those ears went to a regional lab for further analysis.
"We're looking for a random representative part of the field. It's not that we're trying to make a yield estimate for that field, but the sample is drawn to represent the state as a whole," Thessen says.
Darling says a growing challenge in collecting the data is in the number of different production systems farmers use today. Narrow rows can make corn data collection more difficult, for example, as can different tillage systems. "It's rougher with no-till," he says. "Beans in narrow rows make it tough too."
Darling weighs the ears he harvests from the corn field to get an estimate of test weight. Two of the ears collected will go to a regional lab to be more intensively tested for moisture content and shelling fracture. Darling, a former USDA specialist in Washington, DC, monitors 15 fields for NASS.
Darling adds up the numbers after weighing the corn cobs he collected. In this particular field in northern Polk County, Iowa, he estimated the yield to be just short of 186 bushels/acre.
In soybeans, Darling counts plants and pods in 2 rows 3 1/2 feet long. Late September's a lot easier than earlier in the growing season. "The first month you go out there, you better get it into your mind you're going to be there a couple hours," he says. "You're counting nodes and blooms. Could be 100 or more on each plant."
Production estimates from USDA enumerators, all gathered in late September and early October, will be combined with the results of the agency's Objective Yield Survey begun on September 24. NASS doesn't send its recommendations for the Crop Production report to Washington, DC, until the day before the report is issued.