The influence of depth and salinity of watertables on the salt levels in the duplex red-brown earths of the Goulburn Valley of Victoria

Abstract

The results from a survey of 269 test wells in an area with shallow watertables were used to derive a relationship between soil salinity to 60 cm depth (Y) and watertable depth (X1) and watertable salinity (X2). The survey area (730 km2) was in the Goulburn Valley of Victoria and included irrigated and non-irrigated pastures. The relationship was described by the multiple Regression ln Y = a + b ln X1 + c ln X2 The equations were: Perennial pastures ln Y = 7.3859 - 0.607l.ln X1 + 0.2925.ln X2 (r = 0.50, P= 0.0000002, n = 109) Annual pastures ln Y = 7.2690 - 0.7252.ln X1 + 0.3743.ln X2 (r=0.54, P=0.00349, n=36) Dryland pastures ln Y = 10.8417 - 1.3779.ln X1 + 0.4024.ln X2 (r= 0.73, P= 0.0003, n = 24) It was concluded that both depth and salinity of the watertable determine its hazard to soil salinity; watertable depth alone can be misleading. The effect of watertable salinity was greater than that of watertable depth. Similar models could be developed for other regions if data for the regions were available.