Farm Run-off is a common problem, fertilizer gets into rivers and streams causing eutrophic levels of plant life, etc.
Also, all those precious nutrients... lost.
What I propose is that farms be recontured somewhat in the shape of a giant funnel. The very edge of the land will be the highest point,
and it will very gently slope to a central pond.
This pond will be filled with nutrient rich water, and pesticides, and can be reused for irrigation over and over maximizing the gains from any product the crops are exposed to. This will likely lead to reduced dosing needs of both fertilizers and pesticides.
If pond levels rise too high, the water can be removed for treatment, or, alternatively, be sprayed into the air in a manner to optimize evaporation. It will be wise to have a water towers, so as to be able to pump in off-peak hours, and then irrigate via potential energy as convenient.
The pond can be dredged, and the dredged plant matter can be used as fertilizer, or perhaps mulch once dried.
The pond will likely need to be pretty deep, optimally 30 feet at ideally full, with 6 feet extra in case of heavy rain.
With 6 feet of leeway, a 30 acre pond will meet the needs of a 360-acre farm experiencing 6 inches of runoff.
If the farm is flooded, the floodwaters will be stopped to a large degree, reducing damage downstream from the same flood.
It will require some earthmoving to set up a farm like this, but if the farmland stays stable afterward, the efficiencies gained in fertilization will likely be worthwhile.