Benefits from broadcasting cover crops pre-harvest

• Earlier sowing encourages  establishment

• Novel approach uses new seed technology

• Helps workflow and delivers stronger crops

Delaying cover crop establishment until after harvest can mean plants miss the best window for growth – but there is a better way to improve establishment.

Sowing cover crops later often reduces their ability to protect soil, capture and fix nutrients and lower biomass production, says Simon Hobbs, cover crop, environmental and wildflower seeds manager for Agrii.

Broadcasting seed earlier when soils are warmer and days are longer has many benefits. “There are obvious advantages of including cover crops in the rotation but getting the most out of them is not without complications.”

“We’ve therefore spent a fair bit of time looking at how we can maximise the upsides of cover crop use for producers while minimising the challenges.

“One big issue is that cover crops deliver their best results when sown early in the season – but harvest can stretch late into September.

Alternative method

“By this point, soil and air temperatures are declining and shorter daylight hours reduce seed germination and growth, so there is a very narrow window in which to establish the cover before winter and the crop’s growth will inevitably be reduced.

“Ideally, cover crops should be established from mid-July to mid August but because of delayed harvests or in regions where it is normal to harvest later, this is seldom possible.

“If there was a reliable way of establishing the cover crop before harvest this would have many advantages and this is where the challenge lies.”

To address this, Agrii has teamed up with seed specialists Cérience to develop a seed mix designed specifically for broadcasting that allows establishment up to three weeks prior to the planned harvest date, he explains.

“This has resulted in the development of a specific mix containing two species of vetch plus two radish varieties selected for their complementary rooting systems and nitrogen-fixing capabilities which also complies with the requirements of SFI options SOH3 – Summer catch crops and CSAM2 – Winter cover crops.

Technical developments

“Known as the PHAB (pre-harvest Agrii broadcasting) mix, the aim is to allow early establishment to generate more biomass above and below ground, to improve soil structure and to capture and fix more nutrients to benefit the following cash crop.

While all that sounds fairly straightforward, the approach relies on some serious technology on the seed front to make it work reliably and effectively, stresses Mr Hobbs.

“The essential starting point for successful broadcasting is to create even seed distribution, which is where seed coating comes in.

Uniform spread

“In the first instance, the Cérience’s SAS fly coating applied to the seed balances out the thousand grain weight (TGW) of the seeds, allowing the mixture to be spread uniformly up to 36 meters using a standard fertiliser spinner.

“Once on the ground, the dust-free, hygroscopic coating helps the seed absorb moisture to give the cover crop a head start in dryer soils. The coating also contains and organic bio-stimulant to further enhance establishment.

“Plus, to help make sure the approach works consistently in the widest range of different settings, spreader calibration settings are also readily available for common machinery brands including Amazone, Kverneland, Kuhn, KRM Bogballe, Sulky/Sky, and Lemken.”

Easing the pressure

Mr Hobbs believes the ability to broadcast cover crops up to three weeks before the crop harvest date instead of post-harvest is a significant development for growers juggling harvest management pressures.

“Harvest time is one of the busiest periods on any farm, so being able to establish covers earlier in the season helps spread the workload, he says. There are also   clear logistical benefits, the technique offers significant economic advantages, says Mr Hobbs.

“Based on standard NAAC charges, our trials suggest broadcasting cover crops pre-harvest can reduce establishment costs by approximately £50 per hectare, compared to traditional post-harvest drilling.

“These savings stem from lower labour requirements, reduced fuel consumption and machinery costs.”

While pre-harvest broadcasting remains a relatively new practice, early adopters report promising results, Mr Hobbs explains.

“Farms that have trialled the PHAB mix describe stronger, denser cover crops going into winter, better soil protection and improved nutrient capture—all without the time pressures of post-harvest drilling.

“It’s a simple, effective way to improve cover crop establishment, ease the autumn workload and reduce costs,” says Mr Hobbs.