Soil Cutaway (IMAGE) American Society of Agronomy Caption Matthew Walker points to a macropore in which water travelled during the experiment, thus leaving blue tracks or fingerprints behind. The picture was taken while excavating a soil profile, three days after blue-dye water had been sprinkled onto that soil profile. Credit Genevieve Ali Usage Restrictions Please use with story only. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.