Ken Flower – Long term effect of crop rotation and residue on diseases and nematodes

Short bio: Dr Ken Flower lectures and does research in agronomy at UWA. He came to Australia in 2004, from Zimbabwe, and joined the WA No-Tillage Farmers Association (WANTFA), then moved to UWA in 2008 as a lecturer in agronomy. His main focus in the past has been cropping systems with an emphasis on conservation agriculture. Recently he has also been working and teaching on precision agriculture.

Title: Long term effect of crop rotation and residue on diseases and nematodes.

Abstract: A long-term experiment at Cunderdin on red loam soil was started in 2007, to understand the effects of rotation and residue retention on the soil, crop production and disease, under a no-tillage system. The treatments were based on increasing levels of diversity in the rotation from ‘monoculture wheat’, ‘cereal rotation’ (cereal/cereal/cereal), ‘farmer rotation’ (cereal/cereal/break), to a ‘diverse rotation’ (cereal/legume/brassica), and there was also a ‘continuous pasture’ treatment.

The various crop rotations affected soil nematodes and pathogen levels differently after nine years. Fusarium crown rot and Rhizoctonia were favoured by the cereal dominated sequences. Over nine years, fusarium crown rot DNA in the soil increased most in the cereal rotation and wheat monoculture, it hardly changed in the farmer rotation and pasture and it declined in the diverse rotation.

Differences in level of Rhizoctonia were relatively small, although there was a similar tendency for higher incidence in the cereal rotation and wheat monoculture in dry years.

In contrast, Pythium and Root Lesion Nematode (RLN – Pratylenchus neglectus) were favoured by the more diverse rotations. Levels of RLN increased most in the pasture and diverse rotations, followed by the wheat monoculture and appeared to decrease slightly in the farmer and cereal rotations. This was similar to soil Pythium DNA, where levels also increased in the pasture and diverse rotation and decreased in the cereal and farmer rotations and the wheat monoculture.