INTRAPEDAL MACROPORE DISTRIBUTION AND INFILTRATION RATE OF THREE FRIONA POLYPEDONS1

Abstract

We determined intrapedal macropore size distribution and infiltration rate for three Friona fine sandy loam (Petrocalcic Paleustoll) polypedons with different tillage and hydraulic loading histories. One tilled site had been irrigated with treated wastewater, and a second had been irrigated with Ogallala aquifer water. The third site (range) had been neither tilled nor irrigated for at least 15 years. Eight pedons within each of the three polypedons were sampled to determine intrapedal macropore frequency. Fine (1− to 2-mm), medium (2− to 5-mm), coarse (5− to 10-mm), and large (>10-mm) intrapedal macropores were catagorized by size using a hand lens and reticle to measure pore diameter. Within the wastewater-irrigated treatment and the Ogallala-irrigated treatment, fewest fine intrapedal macro-pores were found in the top two horizons. The Btk horizons of the range treatment had the fewest fine intrapedal macropores. These horizons also had significantly lower medium and coarse macropore frequencies within their respective sites. Irrigated pedons generally had significantly greater fine intrapedal macropore frequencies than the range pedons when similar horizons were compared. In general bulk density was inversely related to fine macropore frequencies. The significantly greater infiltration rate, as measured with the flooding-basin cylinder method, of the range polypedon when compared with the tilled polypedons was most likely related to the lower bulk density of the range polypedon. Lack of correlation between intrapedal macropore frequency and infiltration rate suggested that intrapedal macropores were not responsible for a large portion of soil water movement.