Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 2001
Publication Date: N/A
Interpretive Summary: Greater infiltration of rainfall into soil improves crop growth and decreases runoff and soil erosion. On the other hand, pollutants carried with infiltrating water may create groundwater pollution problems. Soil management may alter a soil's ability to infiltrate water. Voids created by tillage and biological channels created by roots, worms, and insects can increase infiltration; wheel traffic compaction will decrease it. We measured the rate of water intake into soil and also studied the pattern of infiltrated blue food coloring added with the infiltrating water. We conducted tests in the planted row, in wheel-tracked row middles, and in untracked row middles for cotton and grain sorghum grown with conventional tillage or no-tillage on a silt loam soil. We found that neither tillage system nor crop affected average ponded infiltration rates but these rates were very different for row positions: 8.65 cm hr-1 for planted rows, 1.86 cm hr-1 for non-trafficked interrows, and 0.24 cm hr-1 for the trafficked interrows. While infiltration rate did not differ with tillage system, dye penetration was deeper and less uniform under no-tillage compared to tilled areas. Thus, we found important systematic spatial variation in water and solute intake patters. These findings are important to scientists interested in understanding and maximizing crop production while predicting and controlling agricultural non-point source pollution.
Technical Abstract: 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 row position would alter the rate and pattern of water infiltration into a Grenada silt loam (fine-silty, mixed, thermic, Glossic Fragiudalfs). We compared planted row, wheel tracked, and untracked row positions for cotton (Gossypium hirsutum L.) And grain sorghum (Sorghum bicolor (L.) Moench)) grown with chisel plow/disk or no-tillage in the fourth year of a cropping system/tillage study. We used ring and tension infiltration measurements 4 to 8 weeks after planting to determine infiltration rate and pore size distribution. Infiltration patterns and mobile water contents were studied by ponding Brilliant Blue FCF dye and excavation. Neither tillage no crop affected ponded infiltration rates that averaged 8.65 cm hr-1 for plant rows, 1.86 cm hr-1 for non-trafficked interrows, and 0.24 cm hr-1 for the trafficked interrows. Sorghum had more pores (0.04 cm3 cm-3) between 1.0 and 0.2 mm diameter than cotton (0.02 cm3 cm-3). Deeper and less uniform dye penetration reflected lower mobile water contents under no-tillage (0.04 to 0.06 cm3 cm-3) compared to tillage (0.12 to 0.23 cm3 cm-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.