Phosphorus between soil, soil water and overland flow for established and laser graded, border-check irrigation systems

Agricultural systems contribute to excessive phosphorus (P) additions that are adversely affecting water resources worldwide. The effects of soil disturbance on P exports have not been widely reviewed. In February 2004, four established and four recently laser graded (<4 yrs) border-check irrigation bays on the Macalister Research Farm (38°00'S 146°54'E) were sampled during and after irrigation. Samples were taken at the channel inlet and every 60 m thereafter. Overland flow was sampled at the wetting front and back up the bays, and soil samples were recovered from the sampling locations two days after irrigation. Overland flow was analysed for total P (TP), the soil samples were analysed for soil Olsen P (0-20 and 0-100 mm depths) and soil water, dissolved reactive P (SWDRP) and total P (SWTP) (0-20 mm depth).