Light plane pilot reported an NMAC with a helicopter shortly after takeoff at OWA airport.

Narrative

On a training flight based at OWA; we were performing stop and go landings on Runway 12. We knew there was an agricultural helicopter performing aerial application work at a low level to the south of the airport. On short final; in our landing flare we heard the helicopter make a radio call that he was to transit over the field at 200 AGL and that he had the landing traffic in sight (us) and that he was going to pass behind us. We performed a stop and go; and performed a short field takeoff as was our communicated plan. On our initial climbout; we look right and the helicopter is approx. 200 feet off of our right wingtip at around 150 feet AGL. The helicopter was not in our line of sight; during our stop and go. Our best evasive action was to continue our flight path and continue climbing into the pattern. We believe that 91.111 was violated in this instance; primarily by the helicopter pilot who was transiting the airport before continuing northbound to their destination.I am unsure of pre-emptive action we could have taken; as we stated our intentions; were the landing/departing traffic at the airport and were flying predictably in the pattern. However; this will continue to be a point of debrief in the days that follow. The only suspicion is if we had not done a short field takeoff; our distance to the helicopter may have been greater. However; it was challenging to know exactly what the helicopters pilot's actions were as we were in our critical phases of flight as we were unable to see the helicopter from our position on the runway.