PGRO Crop Update (06.11.14)

Winter beans
Establishment and seed rates
Sowing and seed bed conditions have been good for winter beans, and growers are advised to drill beans into a minimum depth of 3-5 inches. Don’t delay drilling now if conditions are right. Check thousand grain weight and aim for 18 to 28 plants established per square metre depending on variety. Dense crops of winter beans are more likely to suffer from disease and early lodging.  As a general recommendation a final target of 18 to 20 plants/m² is the optimum for winter beans, which produce several stems.  Recent work by Wherry & Sons has indicated there may be a varietal yield response to population and these are shown in the table below.  A 15 to 20% field loss is assumed when planting beans in the autumn depending on early or later sowing.

Typical final target plant populations
 
Type Varieties Population plants/m²
Winter Beans General 18-20
  Clipper
Wizard, Arthur
Honey, Sultan
22
23-26
28
Spring beans All 35-45

 
The seed rate can be calculated from the following formula:


Seed rate kg/ha =
thousand seed rate x target
populations plants/m²


x

100
% germination 100 – (field loss)


There may be additional interest in pulses following the changes to the common agricultural practice in 2014, and particular attention should be given to seed quality and sowing conditions.
 
Seed quality
Laboratory tests at PGRO indicate that around 20% of winter bean samples tested from the 2013 harvest are infested with stem and bulb nematode, a persistent soil and seed-borne pest, surviving for up to 10 years in soil. Do not to use seed that is infested with stem nematode as there is no chemical means of control once the pest is established and control is based on extending the rotation to avoid planting beans for 10 years. Ensure that all farm-saved seed is tested for nematodes before use.
 
Seed should also be tested for Ascochyta seed-borne disease, which can affect yield and quality.
 
PGRO can carry out both tests and any enquiries can be made by calling 01780 782585.
 
Herbicide applications
Winter beans offer a good opportunity to tackle black-grass populations using Crawler or Kerb. However, early drillings followed quickly by pre-emergence sprays may not fully benefit from Kerb applications, which works better under cooler conditions associated with later applications. Pre-emergence herbicides have a variable but limited time of activity which starts to decrease from the time of application. Winter beans can be in the ground for a long time before the crop is at an appropriate growth stage for post-emergence bentazone, which is less effective in cool conditions. For this reason it may be worth considering keeping an eye on drilled crops and weather forecasts, and delaying pre-emergence applications for as long as reasonably possible. This may extend the effectiveness of applications. This approach offers a chance to move the period of weed control so it is more valuable but does require increased attention to crop and weather conditions and is not without risk.