I believe the tour you're referring to is called
Behind the Seeds. It takes place in backstage areas of the Land pavilion at Epcot. I have taken this tour three times with my kids. the first time when they were 6 and 9 years old. It's a real testament to Disney that my girls begged to back on this tour, which is basically about farming techniques, multiple times. The tour itself lasts about an hour and is run several times a day beginning at a meeting point near the entrance to Soarin'. You can make reservations in advance by calling 407-WDW-TOUR.
In the first part of the tour you learn about using natural methods of pest control. You get to see insects in various growth and development phases. Then each guest on the tour is given a vial of live ladybugs. You are then taken to the fruit and vegetable growing areas. (Much of this part is visible during the Living with the Land boat ride.) The different farming techniques, such as hydroponics, are described. And you get to release your ladybugs onto the crops. The kids LOVE this! You are also given the opportunity to taste something grown in this area. One of the coolest parts for me is when they showed how they grow crops (pumpkins, watermelons) in the classic Mickey shape. I have great photos of my girls holding a Mickey pumpkin. The next stage of the tour involves the aquaculture area where you learn about fish farming. As a bonus, guests are given special pellets to feed fish and alligators. Those things are scary even when they're little.
Overall this is lots of fun, and there's a great educational element snuck in there too. Really worthwhile.