Influences of Aporrectodea trapezoides and A. rosea (Lumbricidae) on the uptake of nitrogen and yield of oats (Avena fatua) and lupins (Lupinus angustifolius)The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Abstract

Summary The earthworms, Aporrectodea rosea and A. trapezoides (Lumbricidae), occur commonly in soils used for grain production in south-eastern Australia, but their distributions are patchy and their abundance low. In a field experiment, inoculations of A. trapezoides , but not A. rosea , increased the growth of oats at early tillering and oat straw and grain yield at harvest. Neither earthworm species influenced the growth and yield of lupins. At early tillering of the oats and concurrent flowering of the lupins, the amounts of 15 N (from fertiliser applied the year before) taken up by both oats and lupins were greater in the presence of A. trapezoides , but not A. rosea . However, there were no differences in the % N in lupin and oat plants between the earthworm treatments. At harvest, there were no differences in the amounts of 15 N taken up by the lupin straw, nor were there in the % N in straw or grain for either lupins or oats between earthworm treatments. The 15 N contents of the oat straw and the lupin and oat grain were higher in the presence of both earthworm species when compared with controls. More than 90% of the N in the lupins was fixed symbiotically. The proportion of fixed N was reduced slightly by A. trapezoides . Inorganic N was analysed at various depths in the soil profile at sowing and early tillering and flowering. An earthworm effect on soil inorganic N was recorded in only one instance – at early tillering / flowering, when soil inorganic N was slightly higher at 0.6– 1 m depth in the presence of A. trapezoides . Management practices, which improve earthworm abundance, in particular that of A. trapezoides , in cropping soils in southern Australia may enhance productivity of some, but not all, crops.