With the dry August halting cover crop drilling, researcher David Purdy is urging caution for those considering September planting.
Although the function of the cover crop species is important when selecting mixtures, ultimately performance is influenced by drilling date and environment.
“It’s important that the species chosen can thrive in the soil type, environment and farming system,” he says. “However, of even greater importance is when it is established. Agrovista’s Lamport project has shown the biomass of a mid-August to a mid-September established cover crop could be as much as 300kg/ha/day.”
He says growers need to remember the life of a winter cover crop is typically circa 120 days. “White clover is an excellent nitrogen fixer but with the limited lifespan of a winter cover, then the nitrogen fixing capacity is already on the limit. If establishment is compromised through later sowing, then so will performance.
“Sow legumes in September and it is unlikely to fix any nitrogen, and small-seeded species could struggle to germinate.”
With showers forecast for early September it might provide the opportunity to get a cover crop away. However, if the conditions are not ideal it might be better to look at a winter cash crop option such as feed barley.
Crop Management Partners agronomist Tristan Gibbs agrees that a catch crop before wheat is a ‘non-starter’. “I would give up now as if it’s dry as it’ll only end up emerging with the wheat if you’re early drilling,” he says.
However, for an autumn cover crop, especially something like an SFI SAM2, he would carry on. He expects rain will arrive at some point and points out many will have earmarked a spring crop anyway. “With sufficient moisture, it should establish adequately from a September drilling. I’m sure we’ll get rain at some point.”
