8 March 2002

Grow organic maize crops

MAIZE crops can be successful in an organic system by modifying crop husbandry and using mechanical weed control, according to one West Sussex-based producer.

Jeremy Burdetts 243ha (600-acre) unit near Haywards Heath is split by two rivers resulting in more than six miles of river boundary, he said. "Concern about pollution was one of the reasons for going organic."

Maize traditionally provided a guaranteed tonnage of forage with a reliable high energy content. But since starting conversion in 1999, low starch in maize has been a problem. He believes dropping P and K fertiliser applications is to blame.

"Grass and red clover leys are now the main source of forage, yielding 15t/acre freshweight in three cuts, while maize yields have fallen from 16t/acre to 12t/acre. The maize area will gradually decrease from 35ha to 15ha during the five year conversion period."

Mr Burdett stressed that growing organic maize in a rotation was essential. He plans to grow it between cereal and legume crops, on IACS land, to prevent weed build up, avoiding known dock and couch grass infested areas.

As with conventional maize, seed-bed preparation is crucial. When the seed-bed is warm, May 15 at the earliest, the crop is drilled 7.5cm (3in) deep using a conventional seed drill, said Mr Burdett.

On some organic units, rooks have been known to eat every seed. But at Cockhaise Farm there have been few bird problems with 120,000 seeds/ha (48,500/acre) sown leading to a stand of 100,000 plants/ha (40,500/acre). Using a conventional drill seems to help reduce rook damage, he said.

"To control weeds, the crop is comb harrowed weekly after five days until it reaches the six-leaf stage. This knocks out weeds in the top inch which can look devastating, but maize plants soon recover."

Another problem with maize is its low protein content and purchased organic protein is expensive. Last year, about 2ha (5 acres) of sunflowers were grown and ensiled with maize in a 1:3 ratio to boost protein levels. But the sunflower crop was fairly inedible and lupins are being tried this year, he added.