This article along with The Hypoxia Report on the Gulf Mexico have identified the problem very well. The solutions are not so simple and those mentioned will do nothing to solve the problem. Buffers do not reduce the concentration of nitrate in solution. Care in the application might be an answer albeit expensive. Farmers in SW Kansas are using precision techniques at $1000 per acre capital cost for micro drip piping. Studies by professor Lamm at Kansas State university indicate that 15 years of use is the payback in fertilizer use savings and energy savings in semi arid conditions.
The only answer that makes economic sense is to return animal production to pasture production which would also reduce obesity caused by corn fed animal products