Crop Growth Stage
Crop growth continues to be slow apart from on some of the peat/fen and lighter soils. The advanced crops are now showing 4 true leaves but this is exceptional. The majority of crops are at the 1st pair of true leaves to 1 cm stage.
Nitrogen
Final nitrogen applications are a priority and should be applied as soon as conditions allow.
Soil mineral nitrogen (SMN) results will be published next week from trial plots where N, at rates ranging from 0 to 250 kg/ha have been applied this spring. This will provide an indication as to where the nitrogen is within the soil profile following recent rainfall.
The N max limit for sugar beet applies to the average nitrogen application rate across the farm for the sugar beet crop. This means that it may be possible, in one or more individual fields being cropped with sugar beet to apply nitrogen at a rate that is higher than the N max limit, provided that the average application rate across the whole area of sugar beet on your farm does not exceed the N Max limit.
The N max limit for sugar beet is 120 kg N/ha.
Note that additional N is allowed above 120 kg N/ha where straw for mulching or paper sludge has been applied. (See NVZ leaflets for more information)
The current BBRO advice is that nitrogen applications must obey NVZ rules and regulations.
Manganese
Where appropriate manganese sprays should be applied when spraying is possible.
Crop grazing
Grazing by birds and mammals continues to be a problem, maintain deterrent activities as appropriate.
Beet flea beetles
There is evidence on some sugar beet plants of damage by beet flea beetles (distinct from turnip flea beetle that feeds on brassica species). Small feeding pits can be found on the cotyledons and young leaves, however new damage does not appear to be present and seed treatments generally provide good control against this pest. With sugar beet growth being slow this season check crops, and in particular backward ones, for any new activity when temperatures increase. There is no treatment threshold for this pest, and foliar insecticides should only be applied if plant loss is threatened or growth is being severely checked and flea beetles can be seen to be active.
Volunteer potatoes
Where volunteer potatoes are starting to emerge, the addition of clopyralid should be included in the herbicide programme. Clopyralid applied in tank mixture with ethofumesate containing products, is the best treatment against volunteer potatoes in sugar beet. The effect on progeny tubers is carried through to succeeding generations, thus reducing the threat from volunteers in the second year after treatment. Note that the new double strength formulation of clopyralid, Dow Shield 400, has been launched, this new formulation contains twice as much clopyralid and is applied at half as much per hectare as that used with Dow Shield 200. The first application of clopyralid should be made when the volunteer potato shoots are between 5cm and 10cm tall.
Herbicides
In most situations weed growth continues to be slow, the exceptions being on the fen/peat soils and some of the lighter land.
Consider options such as the Bayer Flexible and Dupont Broadacre approach where the sugar beet crop will be at the first true leaf stage or beyond when first herbicides are applied. These programmes are based around applying a number of actives at higher rates than used earlier in the season and in commercial trials have given good results.
Other options exist and the BBRO Herbicide Charts 2012 issued earlier this year and also available on the UK Sugar Beet Portal ( www.bsonline.co.uk ) should be consulted.
Black-grass
Where black-grass is expected monitor growth and aim to apply sprays targeted at this weed at the 1 to 2 leaf stage of the grass weed.
Bolting prospects
The chart below shows this year's intensities of vernalization at Bracebridge (Lincolnshire). The graph shows that the seasonal progression since the beginning of March is running ahead of the average for cold springs of the past 25 years. Accumulated intensities at the end of March and April are also given for successive weekly drilling dates. Bearing in mind that the bolting threshold is 140 vernalizing hours, our view at this stage is that we are likely to see significant bolting in early-sown bolting-susceptible varieties, and more than in recent years in early-sown bolting resistant ones if t emperatures remain cool for another 2-3 weeks. We will continue to keep you posted as the season develops.
Re-drilling
Whether or not to re-sow part or all of a field depends upon the plant population which remains, the date on which it was sown, the date on which it is to be re-sown, and the likelihood of achieving a population of at least 75,000 plants/ha when the re-sown crop establishes.
Plant populations need to be below 30,000 (see chart below) now to warrant re-drilling and consultation with your local British Sugar Area Manager is strongly advised if you are contemplating this. The cause of the crop failure must be known, to judge whether or not it will recur at the second attempt.
The graphs below show the likely yields of early and late-sown crops with a range of gappy or irregularly distributed plant populations. The re-sown crop of 75,000 plants/ha must produce more sugar than the gappy crop it replaces, and whether or not this occurs will largely depend upon the date it is sown. The likely yields following a range of re-sowing dates are also depicted.
BASIS points
Two BASIS points in total (not per bulletin) have been allocated for the period between 01/06/11 and 31/05/12 reference CPD/20108/1112/a. In order to claim these points please contact Jill at BASIS registration on Jill@basis-reg.co.uk
For technical queries contact the BBRO helplines:
Pam Chambers: pam.chambers@rothamsted.ac.uk - 07887 628357
Colin Walters: colin.walters@britishsugar.com - 01733 422088
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