A sprinkler system was developed that applied water to quadrant-shaped plots with a uniformity coefficient greater than 90% for any 2-m zone between 3 and 9 m from sprinklers that were located at the vertex of the quadrant. With this sprinkler system, many variables that affect the performance and behavior of herbicides applied in irrigation water can be studied. When applied through this sprinkler system in 1.4 cm of water, alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] at 3.3 kg/ha, EPTC (S-ethyl dipropylthiocarbamate) at 3.3 kg/ha, EPTC + trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 3.3 + 0.6 kg/ha, and EPTC + oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) at 3.3 + 0.8 kg/ha controlled barnyardgrass [Echinochloa crus-galli(L.) Beauv.], common lambsquarters (Chenopodium albumL.), and hairy nightshade (Solanum sarachoidesSendt.) selectively in beans (Phaseolus vulgarisL. ‘Pinto 114’).