If you're not in the field already you will be soon. If you have added extra hydraulic functions, like row cleaner lifters or a downpressure system that runs off hydraulics, will your current tractor have enough hydraulic outlets and capacity to handle the new features? Likewise, if the row cleaner lift is electric or if you're adding new electric drives on your planter, can it keep up and generate enough electricity to power those features?
In the "good old days" of Farmall Ms and John Deere 620s and even Allis-Chalmers 190 XT tractors and John Deere 4430s, the question was usually about whether or not the tractor had enough horsepower to handle the toughest job you would give it. Usually, that meant could it pull as many bottoms on a moldboard plow as the manufacturer said it could.
Today on most large tractors, horsepower is less likely to be the problem than electrical or hydraulic capacity.
One year ago, I rode with a farmer who had to shut down the planter so a repairman could drive into the field and switch out alternators. The night before, his father was planting after dark when the lights went dim. They had added add-ons to the planter powered by the tractor's electrical system. The repairman said the existing alternator was working, but not at a level high enough to keep up. He installed a new one that was producing more power.
In another case a farmer traded up to a 12-row, split-row soybean planter, and had to go with a newer tractor to get enough hydraulic power to lift it and operate it properly. He had been pulling his 8-row split-row planter with a 25-year-old, 140-horse tractor. It did the job, but it didn't have enough hydraulic outlets for the new planter, and it barely had enough hydraulic capacity to make the smaller planter operate properly.
If you've added hydraulics or electric add-ons, you'll find out soon enough if your existing tractor can handle it without modifications. Be prepared to spend some time revamping your current tractor, or switching to another tractor you have with more capacity. You may need a new alternator if the tractor has age on it and you're adding extra drain on the electrical system.
If all else fails, some dealers offer attractive leases on larger new tractor that might get you through this season.