SOYBEAN YIELD AS AFFECTED BY CROP ROTATIONS, DEEP TILLAGE AND IRRIGATION LAYOUT ON A HARDSETTING ALFISOL

The hardsetting surface of many Alfisols in Australia is a limiting fa ctor in crop production. Better soil management systems are required t o improve productivity. This study reports the effects of several unte sted management systems, involving the combined effects of tillage (de ep ripping (Rp), deep mouldboard ploughing (Mb) and disc ploughing (Di sc)), irrigation layout (permanent beds, border ditch) and crop rotati on treatments (single cropping (SC), double cropping (DC) and pasture (P)) on soil structure and the production of irrigated soybeans (Glyci ne max, L.) on a hardsetting Alfisol. It was conducted under a system of controlled traffic near Trangie, New South Wales, Australia. The DC and P treatments increased total water entry and soil organic carbon. Soybean leaf water potential (LWP) improved, and soybean yield was in creased by as much as 58%. The retention of cereal and P stubble appar ently enhanced total water entry by slowing the rate of irrigation wat er advance and by reducing the potential for slaking. The increases in soil water were associated with a reduction in soil strength; a key l imiting factor in crop growth on hardsetting Alfisols. Deep tillage or the use of permanent beds did not affect soybean yields under the con ditions reported in this paper, although the combination of disc ploug hing and furrow irrigation was successful. (C) 1997 Elsevier Science B .V.