Roundup has no carry over. If it does not hit a plant before it hits the ground it is inactive. I asked Monsanto to make some that would last a while on the ground to stop future weeds and was told they would like to but it was impossible because of its makeup. Ed k
My neighbor had a mix of Laudis and Roundup sprayed on his corn early this summer, Laudis will provide residual control, this was the second round of spraying on the field near our house. The first round of pre-planting spray was a mixture of 2,4-D, Atrizene, and fertilizer.
https://www.cropscience.bayer.us/Products/herbicides/laudis/label-msds