Space weather is known to cause disruptions to GPS and communications systems, and perhaps no one is experiencing those headaches more than farmers this weekend. reports that increased solar activity over the past few days has caused the GPS navigation systems that guide some modern tractors from John Deere and other brands to fail. The technology has allowed farmers to sow more efficiently in ultra-narrow, straight lines, but they have been advised to temporarily stop using it because of the potential for inaccuracies that could wreak havoc down the line when it comes time to harvest.

John Deere tractors connect to what are known as real-time kinematics (RTK) systems, 404 reports that allow precision planting down to the centimeter level. If farmers go ahead and seed without their usual accuracy, “we expect the rows will not be where the AutoPath lines think they are” when it comes time to tend and harvest, Landmark Implement, owner of some dealerships in John Deere said 404 Media.

The timing is terrible — it’s peak corn planting season, and one Nebraska farmer, Kevin Kenney, said 404“All the tractors are at the end of the field right now and they’re off because of the solar storm.” Many farms have had to stop planting while others are continuing and just hoping for the best.

The geomagnetic storm we are currently experiencing is the strongest seen in 20 years and reached G5 levels on Friday and Saturday morning, which is considered “extreme”. Later it died down to some extent but it is expected to on Sunday evening, when some intense but slower-moving coronal mass ejections (CMEs) from the sun reach Earth. That’s great, but not so much if your livelihood depends on the technology that the storm interferes with.