Farming is a risky business. Growing food for sale has always been subject to unpredictable weather conditions, shifts in price, and the spread of disease. As of last week, farmers in the United States now also have to contend with the second Trump administration’s tariffs.

On Tuesday, March 4, President Donald Trump levied a 25 percent tariff on all goods imported from Canada and Mexico, as well as a 10 percent tariff on goods from China. The news carried significant implications for farmers who depend on the plant nutrient potash, which the U.S. imports almost exclusively from Canada.

But two days later, amid stock market chaos and criticism from business leaders, Trump exempted some goods from the tax and lowered the tariff on non-exempt potash from 25 percent to 10 percent. Trump’s agriculture secretary, Brooke Rollins, hailed the lower tax on potash as “a critical step in helping farmers manage and secure key input costs at the height of planting season while reinforcing long-term agricultural trade relations.” Although the move was meant to be conciliatory, farmers, agricultural researchers, and economists say that taxing fertilizer at any rate will not only increase costs for U.S. growers, but also could lead to a decline in U.S. soil health.

Most commercially available fertilizers contain a mix of three essential plant nutrients: nitrogen, phosphorus, and potassium. Potash refers to the mined potassium compounds that go into conventional fertilizer. Estimates vary, but the vast majority of the potash used in the U.S. — at least 85 percent — comes from Canada. 

Potassium helps water and nutrients move throughout a plant, and it’s especially important for crops with “large fruiting bodies,” said Stephen Wood, a senior scientist for agriculture and food systems at the Nature Conservancy, an environmental nonprofit focused on land and water conservation. That includes tomatoes, melons, grapes, peaches, and strawberries. It’s also critical for the development of corn and soybeans, which represent roughly two-thirds of America’s commodity crops by acres planted, according to the most recent Farm Service Agency data available.

In the U.S., corn uses more than 2 million tons of potash a year, according to data from the Economic Resource Service, part of the U.S. Department of Agriculture. That’s about a half million tons more than the amount of potash used by soybean crops (around 1.6 million tons), and significantly more than cotton and wheat crops (historically, under half a million tons). That means U.S. corn growers are likely to be hardest hit by the tariff on potash. 

“I think we’re going to see maybe some farmers thinking about, ‘Do I want to grow as much corn?’” said Silvia Secchi, a professor and agricultural economist at the University of Iowa. 

In response to the original version of the tariffs, Kenneth Hartman Jr., the president of the National Corn Growers Association, called on the president to reach a trade deal that would balance national security needs with the needs of farmers. In February, Senator Chuck Grassley wrote on X, formerly Twitter, “I plead [with] President Trump to exempt potash from the tariff.” Grassley represents Iowa, which produces more corn than any other state in the country.

Secchi suspects that it will be hard to measure the exact economic impact that the potash tariff will have on farmers because it is mixed into fertilizers in varying amounts and some crops need it more than others. Bob Hemesath, an Iowa corn grower, said the tariff will hurt all sorts of farmers, given that potash is a key nutrient for all plants. “The 10 percent [tariff] on potash is not good for the ag space or for farming, because it just adds another expense to our already high input costs,” said Hemesath, who is also a board member of the National Corn Growers Association, a trade group.

Other farmers agreed. “It certainly seems to me that Trump is clueless about agricultural policy and how food is produced in this country,” said Wes Gillingham, board president of the Northeast Organic Farming Association of New York. 

It’s also possible that making it more expensive for U.S. farmers to access fertilizer could have a negative impact on soil health, which in turn can determine whether soil stores carbon or releases it into the atmosphere. Research shows that potassium plays a role in helping crops become more resilient against diseases. Gillingham worries that if farmers try to “skimp” on potash, they may try to overcompensate by using additional fungicides and pesticides, which can kill microbes that keep soil healthy. 

These pest killers are not a substitute for plants getting all the nutrients they need, but they may help farmers keep up their crop yields. If the tariffs stick around, it could “push farmers to use less optimal fertilizers or deplete soil health over time,” Mark Schonbeck, a senior research associate at the Organic Farming Research Foundation, said over email. 

Hemesath disagreed that farmers will be more likely to use pesticides, which he said “will not help in replacing potash or any fertilizer.” But he added that if the tariffs are still in place next year, many corn farmers will have to decide whether to make do with less fertilizer or simply to eat the higher cost of potash. 

Another possibility is for corn growers to adopt more environmentally friendly agriculture practices to minimize their need for potash. Michael Happ, the program associate for climate and rural communities at the Institute for Agricultural Trade Policy, said he has heard from large-scale commodity growers who are interested in learning about regenerative agriculture. In general, regenerative agriculture advocates advise farmers to ditch commercial fertilizer and switch to using compost or animal manure to keep crops healthy. Other regenerative techniques — like no-till farming, crop rotation, or the use of cover crops — help carbon and other plant nutrients stay in the ground. 

But the price hike on potash comes at a time when the Trump administration is making it harder for farmers to switch to organic — by erasing USDA webpages that contained information on how to access funding and technical support for these shifts. Last month, Gillingham’s organization and two environmental groups sued the USDA over this data purge. 

“He’s taking away the information, taking away the funding and support for not having to depend on potash imports, and then he’s raising the price of the imports,” said Gillingham. “There’s an irony.”

Happ, from the Institute for Agricultural Trade Policy, said Trump’s attacks on federal workers have also impacted farmers. The USDA fired nearly 6,000 probationary employees last month, though the agency has since been ordered to reinstate the terminated workers for at least 45 days. Trump’s administration is also looking to shut down 59 local offices of the National Resources Conservation Service and Farm Service Agency — two USDA sub-agencies that provide technical and financial assistance to farmers — according to the agricultural publication AgDaily. 

“This is the time where we need lots of expertise and local National Resources Conservation Service officers,” said Happ. “The fact that a lot of these local USDA employees are being fired, and a lot of the local offices are being closed up, it’s happening at the exact wrong time.”

Wood, from the Nature Conservancy, pointed out that large-scale farmers may be best positioned to weather tariff-related price shocks and a loss of USDA resources, because they tend to have more capital. But Colin Carter, an agricultural economist at the University of California, Davis, said altogether, recent Trump policies will likely make things harder for farms of all sizes.

”It’s going to be more difficult for the small farmer, the family farmer, the organic farmer, and the large farmers,” said Carter. “It’s just across the board. I don’t see any winners here.”