DESIGN FOR AN AUTOMATED, SELF-REGULATING, SINGLE-RING INFILTROMETER

Rapid and precise measurement of infiltration in situ is important for characterizing soil properties. We describe an automated, self-regulating, single-ring infiltrometer useful for measuring infiltration rates between 1 x 10(-8) and 3.7 x 10(-3) m s-1. The infiltrometer limits to +/- 1 mm fluctuations in the height of water ponded in a containment ring. Flow rates are calculated from changes in water height in a Mariotte reservoir with time. Water height changes are measured as the difference in pressure between two pressure transducers, one at the top of the Mariotte reservoir and one at the base. Advantages of the new device include (i) accurate adjustment and control of ponded water height, (ii) direct and efficient water delivery from the Mariotte reservoir to the containment ring, (iii) precise infiltration rate measurement, (iv) automated data collection, and (v) rapid setup and movement in the field. The infiltrometer was used to measure infiltration directly over the base of corn (Zea mays L.) plants and in trafficked and untrafficked interrows on a Webster clay loam soil (fine-loamy, mixed, mesic Typic Haplaquoll). Infiltration rates were four to eight times greater directly over the base of corn plants than in nearby interrows.