Seed reserves in temperate Australian rice fields following pasture rotation and continuous cropping.

The size and composition of the soil seed bank of 9 rice fields in the Coleambally Irrigation Area of New South Wales, Australia, are described. Continuously cropped fields were compared with pasture rotation sites. Some 42 species were identified including rice weeds, pasture species and terrestrial weeds but rice weed seeds dominated the counts, with Elatine gratioloides and Cyperus difformis together accounting for 68-99% of the total. Total seed populations ranged from 17 300-646 000 seeds m^-2 with a maximum density of 334 000 seeds m^-2 for E. gratioloides at one site. A close relationship was found between the numerical importance of seed bank species and their occurrence in the rice weed flora. The largest total viable seed population occurred at the site with the longest history of continuous rice cropping, and the lowest seed densities were recorded at sites following a pasture phase. -from Author