SUBSURFACE HERBICIDE APPLICATION WITH THE MODIFIED JOHN DEERE MULCH MASTER

Abstract

Subsurface versus surface application can reduce herbicide losses from surface runoff, volatilization,photodegradation, and windinduced drift. Because distribution in the soil plays an important role in herbicide fate andtransport, this study was conducted to analyze the effect of various application methods on herbicide losses with surfacerunoff. Twelve rainfall simulation plots (three replications of four herbicide application treatments) were established in 1995.Losses of atrazine, metolachlor, and cyanazine with surface runoff were measured for the four different treatments: broadcastspray without incorporation with notill (NT), broadcast spray with disk incorporation (SD), broadcast spray with MulchMaster incorporation (MR), and subsurface application with incorporation using a modified Mulch Master (MB). For themodified Mulch Master, sprayer nozzles were added to the trailing edges of 61cm wide Mulch Master sweeps, which wererun at a depth of 6 cm. Following herbicide application, rainfall was simulated at 6.35 cm h 1 for 1.5 h on the 3.1 m
10.7 mplots. Runoff volumes and soil losses were greatest for NT (3.36 cm and 632 kg ha 1 ), followed by MR and MB, with SDshowing the lowest total runoff and sediment losses (0.34 cm and 217 kg ha 1 ). Herbicide losses and concentrations weresignificantly greater (P = 0.10) for NT than for the other three treatments. On the NT plots, runoff began quickly and onlyoccurred on two of the four interrow areas that had traffic tracks. Herbicide losses decreased in the order of NT, MR, SD,and MB. In addition, MR and MB retained more surface crop residue than SD.