9 January 1998

Cold-tolerant soyabeans

look set for arable prize

Could cold-tolerant

soyabeans grown for

combine harvesting be the

next boom crop for arable

farmers? Alex Odell of Wye

College describes recent

MAFF-funded research

COLD-tolerant soyabeans have been the subject of extensive field trials over the past four years at the University of Londons Department of Agriculture at Wye College, Kent.

UK grown soyabeans are an attractive proposition because they offer complete traceability and guaranteed freedom from genetically modified seed for both human and animal consumption.

This years MAFF-funded experiment looked at the effect of planting date on crop establishment, maturity and yield and the role of nitrogen fertilisers.

Soyabeans are best sown once soil temperatures approach 10C, which means early May for southern England. The trial considered planting dates from mid-April to the end of May.

Pigeon and rabbit grazing and early weed competition can all be problems during establishment, so rapid, uniform emergence from a fine seed-bed, plus early broad-leaved weed control, is essential.

While emergence took 37 days for crops planted early, on Apr 10, planting three weeks later on May 1 reduced that to just 12 days.

Plots were not desiccated to highlight differences in maturity – crop planted on Apr 17 was harvested on Sept 20 compared to the last planting date which was harvested on Oct 9.

However, Thiram seed treatment aided establishment and the weather was warm and dry enough during the autumn for all the experimental crops to mature. Planting date therefore had little impact on final yield, which ranged from 2.6-2.7t/ha (21-22cwt/acre).

In a wetter and cooler year, however, it is doubtful whether late planted crops would dry in the field in early October.

Although soyabeans are legumes the Wye trial shows N fertiliser can raise yield. Unfertilised soyabeans relying on N fixation alone yielded 2.4t/ha (19.5 cwt/acre), compared with 3t/ha (24cwt/acre) where 150kgN/ha (120unitsN/acre) was applied.

However, crops receiving high levels of N produced more vegetative growth and were prone to serious lodging compared to those that had less than 100kgN/ha.

Wye College is now working with Robin Appel to develop an effective weed control programme and methods of estimating heat unit requirements as a guide to possible growing sites. &#42

Soyabeans were successfully harvested with an experimental plot harvester. The upright, woody crop structure helps the crop dry out well in autumn.

New cold tolerant soyabean varieties are single stemmed when planted at 80 plants/sq m (right) and branched at 30 plants/sq m.

Planting date effects

Planting dateApr 17May 1 May 15May 29

Days to emergence30131212

Harvest dateSept 20Sept 22 Sept 30Oct 9

Season length (days)157145139134

Yield (t/ha)2.62.62.72.6