I came across an assertion that next-generation combines are / will be able to load up with herbicides, pesticides, fungicides, and fertilizer all at once, then go through a field, and the cameras on the combine would not only identify whether a plant is a weed or a crop that's supposed to be there, but also whether to apply herbicide/pesticide/fungicide/fertilizer. This could potentially greatly reduce excessive chemical usage, thus by extension reducing run-off, algae blooms, etc. and the effects thereof. It could probably also determine whether the plant needed more or less water, thus potentially optimizing water usage. There would, of course, be risks inherent in and downsides to this technology - it very much fits into the Borlaug school of thought (see The Wizard and the Prophet).
Does anyone have more info on whether this tech is feasible and, if so, whether it's being developed?