In the last picture the disc gangs label H-3 would of been used to build a ridge in flood irrigated fields. In flat planted crops like alfalfa or grain. The ridges keeping the water in a narrow strip to get to the far end of the field in a short time. If you do all the calculations correctly using the right water infiltration rate can be very effective method yet to day. It was very common in the San Joaquin Valley of Calif.

flood irrigation is still very common for cotton and sugar cane.

rice too.