Soybean School: Fighting disease through crop rotation


When heavy summer rains arrive, Albert Tenuta’s phone starts to ring.

The Ontario Ministry of Agriculture, Food and Rural Affairs plant pathologist started hearing from growers across the province in late June as soil-borne disease moved into many soybean fields after a series of pounding rain events.

When soybeans get wet feet in early summer, Tenuta says plants are susceptible to the four key yield-robbing diseases — fusarium, rhizoctonia, phytophthora or pythium.

On this episode of the RealAgriculture Soybean School, recorded at Southwest Crop Diagnostic Days at the University of Guelph’s Ridgetown campus, Tenuta highlights how different crop rotations can play a key role in defending against these diseases.

Tenuta looks at continuous soybeans and notes how the lack of crop diversity can lead to trouble as root rots invade and devastate plants. The crop does better as other crops are added to the rotation. A soybean/wheat rotation, which is very typical in Ontario, offers better defence but struggles in phytophthora prone areas of Ontario. A soybean/corn rotation is a step up in disease defence.

Tenuta says this is likely the benefit of residual nitrogen, which helps the plant establish its root system, helping it better manage the wet soil conditions. The corn/soy/wheat rotation is the best way to beat disease. “We see very little, if any, of the phytophthora in that particular situation,” notes Tenuta.  See video below.

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