BEIJING—China’s COVID-19 curbs are disrupting the supply of fertilizer to the country’s northeastern bread basket just a month away from spring planting, threatening this year’s corn and soybean crops if not resolved soon. Farmers typically have fertilizer prepared in early April before applying to fields later in the month during planting. But China’s worst outbreak of COVID-19 since the pandemic began two years ago have triggered strict controls on movement of people and goods, sharply slowing deliveries. Fertilizer producers, dealers, analysts, and associations said rules requiring truck drivers to take COVID-19 tests every 24 hours, a need to obtain special passes to deliver goods and factory suspensions due to local COVID-19 cases are all contributing to tight supplies. “Production of nitrogen fertilizer and fertilizer preparation for spring planting has been greatly affected,” the China Nitrogen Fertilizer Industry Association said this week. Jilin, China’s second-largest corn-growing province, is among the hardest …