Earthworm activity in irrigated red-brown earths used for annual crops in Victoria

Abstract

Few earthworms were found in January (15 m-2) or September (21 m-2) 1983 in surveys of irrigated soils used commercially for pastures in the Goulburn Valley, Vic.; only the introduced lumbricids were found. No earthworms were found in January 1983 in a survey of irrigated annual crops on similar soils; the soils had each supported irrigated pasture the previous year. However, in carefully managed experimental soils, i.e. with at least 10 t ha-' of cow manure added per crop with mild or no cultivation, used for double-cropping or lucerne, relatively high numbers (up to 86 m-2) of earthworms were present; these included lumbricids, the genera which are usually the most useful in terms of soil structure, and the native megascolecids. No mature lumbricids were found in January in plots without cow manure. Ample food is needed to enable relatively high numbers of lumbricids to develop in row-crops in the Goulburn Valley, and for very high numbers, the surface soil should be kept moist throughout summer. Macroporosity (20-80 mm depth), infiltration and number of biopores (50 mm depth) were each higher in the non-cultivated systems with cow manure than in the cultivated control (no cow manure added). Numbers of biopores in January 1984 were directly related to total numbers of earthworms in January 1984.