French put cover crop case

13 July 2001

French put cover crop case

In France, one growers

farm assessments of cover

crops highlight the potential

to improve output and

reduce pollution. According

to a leading lo-till enthusiast,

the technique could be

usefully deployed here too.

Andrew Swallow reports

WHAT can build soil fertility, increase drilling opportunities, reduce pollution and improve soil structure?

The answer is not some miracle new product, but the cover crop – a technique which appears to have been overlooked in modern farming research, says one French grower.

Philippe Vandeputte grows 220ha (550 acres) of combinable crops near Ecquevilly, west of Paris, and has been using reduced tillage establishment techniques for 10 years.

He is now investigating the potential of cover crops to do part of the tillage work for him. "We noticed a compaction of the soil surface, especially in the winter, and wanted to remedy that by growing cover crops. But we found there is little research on them, so we decided to do our own."

On Aug 17 last year, a 22ha (54-acre) field following peas was sprayed off with glyphosate mixed with 25kg/ha of liquid nitrogen and then planted with 14 different cover crops.

Two months later, the cover crops were sprayed with glyphosate and wheat drilled into them the following day. Assessments of cover crop dry matter, root volume, type, depth, effect on structure and nitrogen absorbed were measured (see table).

Mustard produced the highest dry matter in the two-month growth period, but turnip and phacelia gave the best ground cover, which helped suppress weeds, says Mr Vandeputte.

But turnips effect on soil structure was assessed as weak in both topsoil and subsoil, compared to phacelia, the best for soil structure, which was rated as good and average at the two depths, respectively.

Observations in the wheat suggest there are other lessons to be learned in choosing cover crops. "Where we had a cereal cover crop there is a lot of BYDV. We did not see any aphids but clearly if you a going to use such a cover crop you must be very careful."

Which cover crop will deliver the best wheat yield will have to wait for harvest results, he adds. But plant counts and tiller numbers, notably in wheat following mustard and phacelia covers, suggest yields will make interesting reading (see table).

FW Farmer Focus writer Jim Bullock is very interested in Mr Vandeputtes work, having visited the farm last month. "The improvement in soil structure is impressive. It has got to be better spending a few pence on mustard seed than burning gallons of diesel."

Hanging on to the nitrogen will help fertility and could help win environmentally linked payments in future, he adds.

Later harvest and earlier drilling means establishing cover crops prior to wheat in UK conditions would be tight, but Mr Bullock plans to try the technique prior to winter beans and spring crops this winter.

"We will broadcast some mustard into standing wheat. Besides the other benefits it should make drilling easier, removing moisture and making the surface softer to drill into." &#42


&#8226 Soil structure improved.

&#8226 Drilling easier.

&#8226 Nitrogen trapped.

&#8226 Beware BYDV and slugs.

Cover crop results

Measure Best Worst

Slugs Mustard Ryegrass/ 26/sq m trefoil 2/sq m

Dry matter Mustard Rye 4.31t/ha 0.8t/ha

N absorbed Mustard Rye 90kg/ha 30kg/ha

Wht ppm Phacelia Rye/oat/ 226 Mellilot 173

Analyses and plant counts conducted by iNRA.

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