14 August 1999

Bags of scope to sow low…

Low seed rates are all the talk this season. Tom Allen-Stevens seeks current advice from a distributor and three growers.

WITH the cost of seed rising and the final product falling, advice that seed rates can be cut significantly without affecting yield is welcome news.

Many growers drilling early with certain varieties could be looking at a seed rate of just 100-120 seeds/sq m, which translates into 45-60kg/ha – probably less than half the national average. Theres clearly a saving in seed cost to be made here. But it is claimed that a lower seed rate will also bring about a number of physical benefits to the crop, namely:

&#8226 Each plant should put out stronger and deeper roots

&#8226 Each plant should have stronger, thicker stems

&#8226 The crop should be under less stress

&#8226 The canopy should be less dense.

These are due largely to the fact that each plant will have to struggle less for space and daylight. The knock-on effect could be a crop that is more able to withstand take-all and drought stress and one that is less prone to lodging (and thus requires less growth regulator).

The more open canopy and lower stress could reduce disease pressure, with resulting lower fungicide costs. Finally, fewer plants with larger root balls competing for the same nutrients could result in better grain fill and less ear disease.

And the disadvantages? Most importantly, the consensus is these dont include yield penalty, thing is that, despite talking about lowering seed rates to less than half.

A less dense crop canopy may not be desirable when there is a high weed population, however. Each seed and plant is that much more important, so attack from rabbits or slugs could have a more devastating effect on yield.

With these advantages in mind, as well as the current trend towards drilling early (the first couple of weeks of September), maybe drilling rates should be reviewed.

Peter Gould, western technical adviser from United Agri Products (UAP), points out that more growers are taking a fresh look at their rates: "Id say 90% of the growers I deal with now talk in terms of target plant populations when discussing seed rate.

"Your target population will vary according to soil type, drilling date and variety and its worth noting that Rialto, Charger, Napier and Claire are prolific tillerers. Claire is suitable for the early slot and youre probably looking at a target established plant population of about 80-90/sq m. Napier is more suited to mid to late September with the other two best drilled in October. Seed rates for all of them can be lowered by 50-75 seeds/sq m compared to Consort."

Drop rates

So the scope to drop seed rates is huge, but Mr Gould warns that rates should always be site-specific and advice should be sought.

&#8226 Claire is a new variety set to perform well in the early slot, according to Bill Angus of NickersonUK, but growers should beware that its thousand grain weight is relatively low (about 47g compared to Ribands 52g). He stresses it is imperative to lower the seed rate.

Mr Angus warns too high a plant population may lead to a dense, but lush and weak-stemmed crop, more prone to lodging.

…and reap benefits of earlier drilling

ANDREW Manfield is certain that the crop benefits from low plant populations. "You let more light in and you get thicker stems. With the plants producing 16-18 tillers each, the root ball must also be larger. Some of these tillers may die back, but the roots will remain, leading to a stronger plant. Its undoubtedly true that you get less lodging."

He has experienced problems with wheat bulb fly that can decimate yields at low seed rates, and uses expensive seed treatments. "Low seed rates go hand-in-hand with early drilling and its something were aiming for more and more as seed becomes more expensive. With the advent of hybrids and GM crops just around the corner, its essential to make the most of the seed youre putting in," he adds.

A Herriau precision drill is used when establishing his wheat. "Establishment is inconsistent with a conventional drill – at low rates you need accuracy," he maintains. Otherwise the agronomy of his crop is no different, whatever the rate, although he adopts a relatively low rate fungicide policy over the whole farm.

Seed rates are lowered most where the crop has an early entry (up to first week of October). After potatoes, however, the seed rate is more like 300 seeds/sq m. His Consort, drilled at 110 seeds/sq m, yielded 11.6t/ha.

Good prospects

JOHN Kendal is used to drilling at low rates. Most of his wheat area is grown for seed and he is often relied on to build up stocks prior to a particular variety being launched on the market. He is currently growing 12ha (30 acres) of a Nickerson variety known as WW24, Consort crossed with Woodstock.

He is upbeat about the prospects for the crop: "It looks good overall and were expecting a 12t/ha yield. We received only 410kg of seed, so we did a few modifications to the drill in order to eke it out a bit."

Every other coulter of his pneumatic drill was blocked off, so that the crop was planted in 18cm rows. The main reason for doing this was to allow for hand removal of rogue varieties, but it also served as an effective way to get a decent spacing at such low rates.

Drilling took place on 19 September. "Thats early for us – we usually aim for end of September to early October. The autumn weed control was good and the crop tillered fantastically."

The agronomy was fairly standard otherwise: the crop received a normal dressing of nitrogen with three fungicides (T1 was triazole-based, with strobilurins used at flag leaf and ear wash).

Higher yield

GROWERS in the west are more reluctant to reduce seed rates as low as those quoted elsewhere, but the trend is still the same – for lower seed rates and earlier drilling. Nick Combes is one of the few who have; his Consort drilled at 200 seeds/sq m yielded more than 10t/ha.

All winter wheat on the farm is drilled by 15 September, his Consort being drilled on 3 September. "The seedbed is crucial – its got to be almost perfect. Every seed must germinate," Mr Combes says. He aims for a plant population of about 140 plants/sq m.

He believes the combination of early drilling and lower rates are giving him higher yields. The low rates especially have encouraged the crop to become more open and tiller out. He has noticed less lodging, too, but this may be due to his early application of Meteor (chlormequat). Fungicide applications may even have risen slightly on the low seed-rate crops. Otherwise, agronomically they are treated very much like any other wheat crop.