The longest maturity in the tax-free sale is due in December 2025. It was priced to yield 5.3 percent, down 0.1 percentage point from earlier in the offering, according to three people familiar with the sale. It’s about 3.27 percentage points more than benchmark munis maturing in 12 years, data compiled by Bloomberg show. Standard & Poor’s rates the securities BB-, three levels below investment grade.

Investors said before the sale that the debt could price as little as 1.8 percentage points to 2.18 percentage points more than top-grade munis.

The bonds were sold to individuals and institutions. Yields dropped by 0.075 percentage point on the portion maturing in 2019 and 0.05 percentage point on the segment due in 2022.

The borrowing is the largest this week and the biggest for an Iowa issuer since at least 1974. It is benefiting from demand for high-yield securities, which have earned 2.8 percent this year, compared with 1.3 percent for the broader $3.7 trillion municipal market, Barclays Plc data show.

Proceeds will fund the building of a 320-acre nitrogen fertilizer plant by Orascom Construction Industries, Egypt’s biggest publicly traded company. The factory will be in Lee County, in the southeast corner of the state.

The deal comes two weeks after an explosion at a Texas fertilizer distributor killed 14 people and flattened 50 homes.