DowDuPont Inc. cut the asset value of its DuPont Co. agriculture business by $4.6 billion, less than nine months before a planned spinoff of the seed-and-pesticide unit.

The impairment charge reflects weaker markets for farm products since last year’s merger with Dow Chemical Co., DuPont said in a regulatory filing. Reduced planting areas and delays in product registrations mean that sales will grow more slowly, while an unfavorable shift to soybeans from corn in Latin America will dent profits.

The disclosure continues struggles in agriculture that DowDuPont has highlighted in recent quarters. Farmers in Brazil are planting more soybeans and less corn, for example, to capitalize on China’s retaliatory tariffs against U.S. soybeans. Currency weakness in Brazil, a key market, is also weighing on DowDuPont’s farm business.

The DuPont operation’s values were set just over a year ago, when the merger with Dow was completed. Since that “high water mark,” the economic outlook has worsened, reducing the book value of those agricultural assets, Laurence Alexander, an analyst at Jefferies LLC, said in an investor note Friday.

Accounting ‘Messiness’

“The disclosures call out slower growth prospects, delays in commercialization schedules and rising R&D costs as key factors,” he wrote. The value of the combined DuPont and Dow agriculture businesses, to be spun off as Corteva Agriscience, isn’t necessarily affected, demonstrating “the messiness of merger accounting.”

DowDuPont’s statement late Thursday said the disclosures don’t change the company’s earnings expectations.

The shares fell 1 percent to $58 at 10:42 a.m. in New York, shaking off a steeper decline before regular trading opened. The shares had declined 18 percent this year through Thursday, while a Standard & Poor’s index of materials companies dropped 12 percent.

Alexander said he “would not be surprised” to see goodwill cut at other DowDuPont businesses “if the economic outlook darkens” in the next year or two. He cited Electronics & Communications, Transportation & Advanced Polymers, and Packaging & Advanced Polymers as candidates. The latter is set to become part of the new Dow when it’s spun off in March. The others are slated for the new DuPont, which will stand alone after Corteva is separated in June.

China Delays

While the asset writedown mostly reflects previously disclosed information, it’s now apparent that China is delaying approvals for Enlist and Conkesta genetically modified seeds, Jonas Oxgaard, an analyst at Sanford C. Bernstein, said in a note.

The chemical giant also filed an initial registration statement for Corteva with securities regulators and said the separation remains scheduled for June 1. The filing provides an overview of the business as well as historical financial data.

Corteva’s slumping seed sales reduced first-half earnings 2.5 percent to $2.26 billion, according to the DowDuPont’s filing.