I found an issue to do with the improved farm, haven't tried basic farm to see if its the same. But after planting a seed, at any point between the first sapling appearing, till the point just before the crop forms, setting fire to it, instantly turns into a cooked version of whatever crop it would have become.
Steps to Reproduce
plant the seed in the improved farm, at any point between the first sapling appearing till the the point before the crop appears, set fire to it.
plant the seed in the improved farm, at any point between the first sapling appearing till the the point before the crop appears, set fire to it.