Yes, it's true ! Here's an old "Combine". It is called a Combine because it COMBINES the Seeds and the Fertilizer together to go into the soil as it is towed behind a tractor.
This one is very old, maybe it was used 80 to 100 years ago. There are separate compartments for the seed and fertilizer. The forward motion of the tractor drives an augur type system within the machine which feeds the seed and fertilizer down some pipes to the soil where it gets applied in a set ratio. The farmer will adjust some openings inside the machine to set the ratio of seed and fertilizer to be sown.
You can see the top ( timber ) compartment here, which holds the fertilizer. Be careful when opening this to have a look , because a lot of the time, a 12 foot long, big fat Carpet Snake ( Python ) sleeps in here. He/she also takes up residence in the roof of our Farmhouse, where the rats and mice make a tasty meal. It is quite a shy Snake, and does not hang around for long once discovered. We love our big Python, it's part of the Family !!