Honestly I think they had totally different designation system back then but he had a lot or responsibility. One time he was standing in front of formation and a Lt. with the brass in the jeep drove over his big toe. While he was in the infirmary they came through and tried to give him a purple heart, he said he wouldn't accept it for getting his toe run over by a lieutenant that cant drive a jeep. He had plenty anyways.
He told me tons of stuff about his experience, I was the only one of his children or grand children that took interest.
More important for testing the input PPM of your feed mixes. If you have plenty of runoff when you water/feed then the runoff shouldn't ever get high. If you ever bone up for a bad ass pH meter, I highly recommend the bluelab digital soil pH meter, you can measure the root zone pH in the soil and it works on liquids just fine.