GQ, to answer your question-crop or stock.
Stock is never good - if at all possible, avoid fields with livestock.
Not quite correct- sheep & horses are no real problem if they move out of the way! Avoid ostriches, cows & bulls.
Crop is OK if you land with the furrows, if you land across them you will probably overturn.
Most students seem to think they need to pick a field that looks like a 1000 metre private strip and is perfect-you just need the best clear area which is not going to damage you!