Field infiltration rates
Double-ring infiltration setup
Field infiltration rates measure the rate at which water infiltrates the soil – not to be confused with hydraulic conductivity of the soil. It is important to the study of runoff, erosion, water availability to plants, irrigation, drainage, and raingarden performance. Infiltration is measured under steady state conditions. The rate is influenced by soil moisture or, more specifically, water-filled pore space, soil surface conditions, degree and type of cultivation, compaction, soil horizon changes, and the season.
Infiltrometers are used to measure field infiltration rates. An infiltrometer set consists of two rings of different diameters pressed concentrically (double ring) up to 5 cm into the soil. A constant head of water, 2–5 cm, is maintained equally in both rings, and the rate at which this water infiltrates the soil in the central ring is measured. The water in the outer ring helps prevent lateral flow in the central (measurement) ring.
We have a Hilux 4X4 and trailer unit containing all equipment and 1000 L water for measuring infiltration rates in the field. Infiltrometer ring set sizes used are: (diameters, outer & inner rings) 500 mm & 300 mm, 300 mm & 200 mm, and 200 mm & 100 mm.
A set of at least four measurements are usually made for each treatment/site, and results are given in m/s and mm/hr.
Reference:
Bouwer H 1986 Intake rate: cylinder infiltrometer In: Klute A ed. Methods of soil analysis: Part 1. Physical and mineralogical methods. 2nd edn. Madison, WI, ASA & ASSS. Pp. 835–836.
Sample Collection
At Manaaki Whenua – Landcare Research we are able to sample soil in bulk or in undisturbed core forms. Many of the tests in soil physics require careful sampling of intact, undisturbed soil to retain structural integrity. This is best done by experienced personnel and we prefer to carry out sampling for what we analyse. Sampling to 0.5-m depth is performed by hand, but deeper samples require soil pits to be mechanically dug or the use of our drilling rig, which can operate to 4 or 5 metres.
* Available only at Palmerston North
# Available only at Hamilton