| A subsurface jet injector was designed, constructed, and tested to incorporate herbicides into soil in a single pass, control established weeds, and retain plant residue on the surface to reduce soil erosion. The design overcame problems inherent in earlier subsurface injection machines such as difficulty in managing residues, placement of herbicides in a layer, and poor depth control. The jet injector incorporated herbicides by jetting them up through nozzles in a manifold attached to a sweep, into soil that was fractured while passing over the blade. Jets penetrated up into the soil, improving weed control. Diffusion or mechanical mixing moved herbicides into untreated soil between herbicide bands.;Relationships among jet penetration distance, nozzle size and type, and sweep operating variables were studied by injecting a fluorescent tracer through the injector sweep or down into disturbed soil. Results confirmed theory predicting jet penetration distance in both soil conditions. Penetration distance depended on herbicide carrier volume, operating pressure, ground speed, soil moisture, and type of soil failure.;A field size subsurface herbicide jet injector was constructed on a sweep plow. A treader was attached to the rear of the plow to mechanically mix herbicides after injection. The machine was tested in corn and soybeans under two tillage systems. Results showed subsurface jet injection of herbicide produced crop yields and weed control comparable to tandem disk incorporation with both systems. Injection at 1400 kPa with the treader attached was the best subsurface jet injection treatment.;Nozzle spacing, orifice size, and operating specifications were determined. Nozzle spacing was found by measuring weed control from trifluralin ((alpha),(alpha),(alpha)-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) injected in parallel lines into greenhouse flats. Herbicide was applied through a 50.8 cm jet injector sweep to test, in the field, the two best nozzle spacings determined in the greenhouse experiment. Nozzles spaced 2 cm apart produced the best weed control. A computer simulation of trifluralin diffusion between jet bands showed the herbicide required 4 to 8 days to diffuse between 2 cm bands. Soil compaction reduced the rate of diffusion. |
