TRAFFIC EFFECTS ON WATER INFILTRATION IN CHISEL-PLOW AND NO-TILL SYSTEMS

Traffic effects on pore structure and hydraulic properties of soils ma y be affected by site-specific factors. The objective of this study wa s to determine if the effects of wheel traffic on infiltration rates i n chisel-plow and no-till tillage systems differed among five Midweste rn locations. Ponded and unsaturated (30-, 60-, and 150-mm water tensi on head) infiltration rates were measured sequentially using infiltrom eters after removing surface residues and the upper 2 cm of soil. Whee l traffic reduced ponded infiltration rates in both tillage systems at all locations, ranging from 95% in the chisel-plow system in Iowa to approximately 55% in the chisel-plow system in Missouri. Tillage syste ms significantly affected ponded infiltration rates at only two of the locations. At the Minnesota and Nebraska locations, no-till reduced p onded infiltration rates in untrafficked interrows by 33 and 64%, resp ectively, compared with those in the chisel-plow system. Ponded infilt ration rates of trafficked interrows did not differ between tillage sy stems at any location. At the Iowa and Nebraska locations, the decreas e in infiltration rate with an increase in tension head was greater fo r untrafficked interrows than for trafficked interrows in the chisel-p low system. The large pores that drain at 30 mm of tension head accoun ted for a lower percentage of the water how with pending in trafficked interrows (73%) than in untrafficked interrows (88%). Infiltration ra te comparisons between tillage systems should consider wheel traffic p atterns.