Tillage and Row Position Effects on Water and Solute Infiltration Characteristics

Biological channels and wheel track compaction zones increase heterogeneity of soil properties affecting infiltration, runoff, erosion, and solute movement. We hypothesized that crop, tillage system, and position relative to the plant row would alter the rate and pattern of water infiltration into a Grenada silt loam (fine‐silty, mixed, active, thermic, Oxyaquic Fraglossudalfs). We compared plant row (ROW), nontrafficked (UTK) and trafficked interrow (TRK) positions for cotton (Gossypium hirsutumL.) and grain sorghum [Sorghum bicolor(L.) Moench] grown with chisel plow, disk, or no‐tillage in the fourth year of a cropping system and tillage study. We used ring and tension infiltration measurements 3 to 10 wk after planting to determine infiltration rate and pore‐size distribution. Infiltration patterns and mobile water contents were studied by ponding Brilliant Blue FCF dye [(N‐ethyl‐N{4‐[(4‐{ethyl[(3‐sulfophenyl)methyl]‐amino}phenyl)(2‐sulfophenyl)methylene]‐2,5‐cyclohexadien‐1‐ylidene}‐3‐sulfoben‐zenemethanaminium hydroxide inner salt, disodium salt)](PYLAM products Co., Garden City, NY) and excavation. Neither tillage nor crop affected ponded infiltration rates that averaged 86.5 mm h−1for the ROW, 18.6 mm h−1for the UTK, and 2.4 mm h−1for the TRK position. Sorghum had more pores (0.04 m3m−3) between 1.0 and 0.2 mm diam. than cotton (0.02 m3m−3). Deeper and less uniform dye penetration reflected lower mobile water contents under no‐tillage (0.04 m3m−3) compared to tillage (0.20–0.27 m3m−3). This research confirmed the importance of continuous macropores in solute movement, but ponded infiltration rates were only weakly correlated with maximum dye depth and did not reflect tillage system differences in dye patterns.