Crops notes November 2006

The mild weather during October has encouraged rapid weed growth in early drilled crops. Aim to apply a residual herbicide to wheat and barley crops while weeds are small. Annual meadow grass, in particular, will be difficult to control once it has begun tillering. The choice of herbicide treatment may be influenced by the weed species present, but a broad-spectrum product based on either isoproturon + diflufenican (Panther), or isoproturon + pendimethalin (Encore), is likely to be suitable. Where a wild oat problem is anticipated, chlorotoluron may be preferable to isoproturon, but check first that your variety is chlorotoluron-tolerant.

Wheat is much more tolerant of later sowing than barley or oats. However, seed rates should be increased to combat the effects of lower soil temperatures, cloddy seedbeds and pest attack which combine to reduce the percentage plant establishment as sowing is delayed. Seed rates of between 400-500 seeds/m² would be appropriate for sowings in November with the higher seed rates being used in more difficult conditions and as sowing is further delayed. This would translate to seed rates in the range of 180-225kg/ha (11.5-14 st/ac).

It is now past the optimum sowing date for winter barley. Even with increased seed rates, crops drilled from November onwards rarely produce high enough yields to justify sowing winter barley in preference to waiting for four to five months and sowing a spring variety as early as soil conditions allow.

Spray an approved aphicide at the end of migration (usually around the end of October, but later in mild autumns) to prevent spread BYDV within the crop by the wingless offspring of winged migratory aphids.

Monitor all crops throughout the winter, including those already treated, on warm sunny days for aphids and spray if they are readily found.

Check soil temperatures and avoid harvesting in cold conditions. Potatoes are much more susceptible to damage below 10^oC.

Handle potatoes as gently as possible. Check that the harvester is correctly set and that any parts of the harvester that could cause damage are attended to.

Use the minimum agitation necessary and maintain a soil cushion as far up the primary harvester web as possible.

Minimise the drop between the harvester cart elevator and the bulk trailer or box. Fall breakers or padded landing areas should be used to reduce impacts.

Assess levels of damage regularly for both external damage and bruising. ‘Hot-boxing’ by placing tubers under high humidity and temperature gives an early indication of bruising problems.

With potatoes likely to be coming into store wet, drying is essential to help maintain crop health and quality. A number of systems can provide forced ventilation needed for effective drying. Systems such as the Wedderspoon tent or Pirie Boxer are suitable for boxes, while a number of systems can dry bulk piles such as below pile ducts and pedestals.

The wound-healing period should be kept to a minimum of two weeks. Humid air in the store should be changed by ventilating on dry afternoons. Crops that contain more than 1percent blight or soft rots should not be cured but marketed as soon as possible as there is a high risk of widespread rotting during storage. Following curing, store temperature should be reduced slowly by approximately 0.5^oC/day to the desired holding temperature. If possible continue to ventilate periodically throughout the storage period as a precaution against rots, or at least regularly inspect the store and remove any problem material immediately.