The effect of crop rotations in the Victorian Wimmera on the cereal cyst nematode (Heterodera avenae). nitrogen fertility and wheat yield

Abstract

Rotations of two or four years sown barrel medic pasture, or volunteer (non-medic) pasture, were compared with a fallow-wheat rotation at Natimuk in the Victorian Wimmera. The fallow-wheat rotation maintained a high population of cereal cyst nematode and a low level of nitrogen fertility. Increase of fertility was greatest under barrel medic (0.006 per cent total nitrogen per year). Though lowest nematode populations were recorded after four years barrel medic plus fallow (0.25 eggs per gram of soil), a shorter period of medic ley may be more practical. Wheat yield following wheat-fallow (24.2 bushels an acre) was increased after two years natural pasture plus fallow (38.4 bushels an acre) but almost doubled after two years barrel medic plus fallow (46.0 bushels an acre). A single years fallow reduced the nematode population by 56-75 per cent, but there was a rapid increase whenever wheat was grown. Following two years medic ley plus fallow, only one or two wheat crops could be grown on a fallow-wheat rotation before the nematode population returned to its original level.