Runoff collecting and nitrogen-phosphorus monitoring system for rice-wheat rotation system

The invention relates to a runoff collecting and nitrogen-phosphorus monitoring system for a rice-wheat rotation system. The runoff collecting and nitrogen-phosphorus monitoring system comprises runoff tanks, collecting barrels, runoff pipes and grid covers, wherein water outlets (7) are formed in the bottoms of the runoff tanks; scales are formed on the walls of the runoff tanks to measure runoff volume roughly; a collecting barrel support (6) is arranged at the bottom of each runoff tank, and used for fixing the corresponding collecting barrel collecting runoff water when the runoff volume is relatively low; one end of each runoff pipe (4) is fixed in the runoff tank, and bent downwards to for conveniently collecting the runoff water; the other side of each runoff pipe is arranged in a rice-wheat rotation field; three water inlets are formed in each runoff pipe; each first water inlet is 5-7 cm higher than the rice field, used for collecting the runoff water during a rice season non-drying period, and covered during other periods; each second water inlet is flush with the surface of the rice field, used for collecting the runoff water during a rice planting soil drying period, and covered during other periods; each third water inlet is formed in the bottom of the corresponding runoff pipe, flush with a corresponding ditch bottom formed by ditching in a wheat season, and covered during other periods; the grid covers are arranged at the exteriors of the water inlets of the runoff tanks; the upper ends of the grid covers are opened; pebbles are paved in the grids.