Rates of soil applied herbicides vary according to soil types because soils affect herbicide activity. In some instances the same rate may be suggested for both medium and heavy soils. Herbicides should be applied in enough water to assure distribution over the area treated. That amount may vary from 5 to 40 gallons per acre on a broadcast basis. Wettable powder formulations require at least 50 mesh screens throughout the spray system and nozzle tips with a capacity of 0.2 gpm or larger.
Considerable agitation is necessary to keep wettable powders in suspension.
Hardened stainless steel and nylon nozzles are more resistant to wear from the application of wettable powders than brass nozzles. Tanks made of aluminum, fiberglass or other corrosion resistant materials will reduce the amount of nozzle clogging. Some herbicides may not be used in unlined steel tanks. Be sure that the water used as the spray solution is free from trash and other foreign material, particularly mud or soil particles. Correct calibration is of utmost importance.