BSK said:
What would be the symptoms of over tillage?
BSK, I worked all day today with my soil scientist, and we had a chance to discuss this topic. I mentioned to him the soil types you are working with, and of course, he is familiar with your area. Basically he told me that the potential problems I mentioned were correct in regards to continual tillage.
Also, as far as additional issues over time, he said annual tillage will bring additional rocks towards the upper part of the soil profile, which inhibits water infiltration. He also mentioned that additional problems you may encounter would include a tillage pan, soil erosion, weathering, excessive leaching of nutrients, and of course decreased organic matter that is extremely critical for retaining moisture.
One of the biggest problems encountered during the summer is moisture retention in conventional tillage situations. We ran some tests this past summer with temperature probes on tilled vs. no-till soils. During the hotter parts of the summer when air temps exceeded 95 degrees, actual soil temps on tilled ground exceeded 110 degrees due to a lack of residue. As a comparison, a hay field adjacent to the site had a soil temp of 78 degrees. What's important to know is that once soil temps exceed 90 degrees, about 90%+ of moisture is lost due to evaporation. So even though you may think you are getting adequate rainfall, it leaves the system very quickly and is not useable by plants.
I know the soil types you are working with because I've seen them a thousand times, so I would just caution you on your current cropping system. I would seriously think about at least going to a longer rotation before any type of tillage is initiated. Just something to think about.