Sow for success
Sow for success
Theres a gap when it comes to performance data for early or late drilled wheats, says one plant breeder. Gilly Johnson reports on trials aiming to put this right.
WHEN choosing a wheat variety, its rare that growers take into account how time of sowing might affect yield performance, says John Blackman of CPB Twyford.
A dangerous omission, he thinks. Like children, varieties develop best under individual management. One wheat might be best suited to early sowing, another develops fast and would need a later slot.
These differences can be extreme, even with wheats that might be thought of as standard winter wheats. And given the current fashion for early drilling, some growers are going to come unstuck, he feels.
"A few wheats do respond to early drilling, particularly those with eyespot resistance such as slow developers Lynx and Genghis. But if this resistance is combined with fast development, then you could have a problem."
But where should growers go for information? The variety bible, the UK Recommended List, is used as the universal yardstick. Well and good as far as it goes, but yield ratings are given only on the basis of early October sowings, and so dont tell the whole story. Figures from the late autumn sown trials for certain wheats dont find their way into the main RL database.
An attempt is made by NIAB to extract more from its data; yields are teased out before and after the average sowing date, and results displayed in the annual handbook. But this isnt enough, he says.
As a plant breeder, he cant afford to ignore performance differences. Given the lack of official trials data on variety/sowing date interactions, hes doing it himself. And we shall be covering the results exclusively in Crops.
Fully replicated trials are now drilled up at Thriplow, on the doorstep of the companys headquarters near Royston, Herts. Hes using all the mainstream wheats, not just the companys own, as well as a few newcomers which are further back in his breeding programme. The full list of wheats is given in the table.
This trial follows a preliminary experiment last year. But this was ravaged by eyespot and lodging, particularly with the early drillings, which threw a question mark over some of the results (see table). This season Mr Blackman aims to eliminate effects from disease and lodging so that variety differences come through clearly. A comprehensive fungicide and growth regulator programme is planned. Unix (cyprodinil) went on in autumn – admittedly a drastic tactic – to keep eyespot out of the early drilled plots.
Walking the plots in the beginning of March, no disease was visible, bar a small amount of mildew on early drilled Claire that will be cleared out with the first all-embracing T1 spray. Nitrogen treatments will go on late in April and May for all sowings – theres plenty of residual N left from a previous pea crop to keep the crop happy. Soil type is light chalky loam, with good yield potential and not too drought-prone.
The six sowing dates have been chosen to test the varieties to the limits: 1, 14 and 28 September, 20 October, 15 November and 10 February. Seed rates are graduated to suit, though at 150 seeds/sq m, the first drillings "may be a touch too low"- perhaps showing an over-reaction following last years problems with the early plots? The complete run-down from early to late goes from 150, 220, 250, 300, 350 and 400 seeds/sq m.
Late drillings will give as much useful information as the early sowings, says Mr Blackman. "The latest safe sowing dates given in the Recommended List can be misleading. Growers might think its okay to go in that late – but then find the crop yields virtually nothing. Safe means that the crop will come into ear; it doesnt say anything about what this late drilling might do to performance. Some varieties, Charger for example, have a high vernalisation requirement."
He is dubious about the benefits of very early drilling. "On this site, the optimum sowing date has been 25-30 September consistently. Weve never been able to demonstrate an advantage from sowing earlier. Id caution anyone whos going down this route."
Like other plant breeders, he is seeking new varieties which can exploit the early drilled slot: "theres the potential for higher dry matter. But were not there yet, and Im not convinced any other breeder is."
In March, the early sowings were thick, lush and forward. Spring wheat Samoa, a fast developer, was already at third node (GS33) – and although the winter had so far been kind, these forward plots are vulnerable to late frosts up until April.
A similar trial is under way with winter barleys, using three sowing dates: 10 and 30 September, and 25 October. Fourteen varieties including Regina, Fanfare, Pearl, Heligan, Artist, Vertige, Muscat and Intro are being compared.
"Of our own barleys, we know that Vertige is an early developer; if drilled too early, then it can flower in April and be at risk of frost. And Intro is better drilled from October onwards."
• Both the wheat and barley sowing date trials will be open to Crops readers for viewing this summer.
Sowing date 1 Sept 15 Sept 12 Oct 20 Oct 10 Nov 16 Feb
Variety
Lynx 115 111 98 98 97 102
Malacca 118 102 95 100 103 101
Riband 111 107 103 101 96 87
Rialto 100 102 100 102 95 91
Equinox 117 108 99 99 98 96
Aardvark 129 116 109 104 111 106
Savannah 79 110 108 105 97 98
Hereward 100 95 94 92 91 64
Cadenza 66 76 106 104 104 128
Genghis 124 117 101 98 104 109
Samoa 77 64 87 96 93 97
Chablis 65 92 100 100 110 120
Mean t/ha 10.22 12.05 11.56 12.61 11.68 7.10
Key: rep removed
result affected by more than 10% lodging
Source: CBP Twyford
Wheats included in the 2000 trial:
Aardvark, Biscay, Cadenza, Canterbury, Chablis, Charger, Claire, Coded new variety, Consort, Equinox, Genghis, Lynx, Madrigal, Malacca, Rialto, Riband, Samoa, Savannah