An agricultural implement (10) includes a chassis (18) and a shank (22) or shanks (22) carried by the chassis (18). The shank (22) or shanks (22) include an on-the-go nitrate-N sensor (42) or sensors (42). Nitrate-N conditions are determined for at least first and second zones (46 and 48) at different soil depths (32 and 50), either by multiple sensors (42) carried on one or multiple shanks (22) during a single pass of the agricultural implement (10), a single sensor (42) carried first at the first depth (32) and thereafter at the second depth (50) during multiple passes of the agricultural implement (10), or a sensor (42) moved between the first and second zones (46 and 48) during a single pass of the agricultural implement (10). Rates for applying additional nitrogen can be calculated from the determined conditions, and the application rates and determined conditions can be mapped.
