Studies on seed pelleting as an aid to legume seed inoculation. 3. Survival of Rhizobium applied to seed sown into hot, dry soil

Abstract

Seed of four legume species with various forms of lime pelleting and inoculation was sown into hot, dry soil at Katherine, Northern Territory, where it lay dormant for 7-9 weeks before germination commenced. Seedling nodulation was used as the index of inoculant survival. Where the seed was sown at a shallow depth, Rhizobium survival was poorer than on seed sown more deeply; this was attributed to the higher temperatures near the soil surface. Rhizobia survived best in those treatments in which peat inoculant was incorporated within the pellet. Rhizobium meliloti applied to Medicago sativa seed showed a high degree of tolerance of the conditions and seedling nodulation exceeded 90 per cent in several instances. Nodulation of Trifolium pratense and T. rueppellianum never exceeded 50 per cent and little nodulation occurred with Lotus pedunculatus. It is concluded that lime-pelleted Medicago seed with peat inoculant incorporated within the pellet can be sown into hot, dry soil with a strong expectation that the inoculant will survive and the seedlings nodulate.