EFFECT OF LUPINS AND PASTURE ON SOIL ACIDIFICATION AND FERTILITY IN WESTERN-AUSTRALIA

An 'across the fence' comparison of farmer paddocks with nearby vir-in bush sites was made at 3 locations, to measure the effects of lupins and subterranean clover based pastures on the chemical properties of t he soil. Estimated rates of acidification in the 0-60 cm depth were 0. 29-0.55 kmol H+/ha.year for wheat-lupin paddocks and 0.16-0.21 kmol H/ha.year for pasture paddocks. A significant proportion of this acidif ication occurred below 20 cm, particularly in the lupin paddocks (up t o 70% of the total). Severe water repellency had developed at 1 locati on that had produced 30 lupin crops with the occasional wheat crop. De spite these detrimental effects, lupins maintained soil mineral nitrog en and organic matter contents and electrical conductivities similar t o those in pasture paddocks, even though the soils in the lupin rotati ons had been sown to wheat more frequently.