Crops notes April 2004

Local research by The Agricultural Research Institute of Northern Ireland at Hillsborough has shown that late sowing is a major factor limiting yields of spring barley. Growers should complete spring barley sowing as soon as possible using seed rates between 160kg/ha (10.2st/acre) and 180kg/ha (11st/acre).

As crops begin to emerge look out for signs of leatherjacket damage, especially in crops following grass or grassy stubbles. If a problem is suspected, search for the pest in ten randomly selected 30cm drill lengths. Treat the crop with chlorpyrifos (for example, Dursban) if more than ten leatherjackets are found in any of the selected areas.

Growth stage 31 (first node detectable) should be the timing for the main nitrogen top dressing in winter cereals.

All cereals, especially those on light, sandy or free-draining soils, are at risk from sulphur deficiency because of reduced deposition in rainfall. At risk crops should receive 15-25kgS/ha in spring. The sulphur needs of crops are most conveniently met by applying a sulphur-containing nitrogen fertiliser.

The key growth regulator timing in winter wheat crops is early stem extension (GS30-31). A chlormequat or trinexapac-ethyl based product should be applied at this time to all but the thinnest crops as a precaution against lodging.

Good soil conditions in the autumn allowed the timely application of residual herbicides to crops at Greenmount. Consequently, cleavers are likely to be the only weed requiring further attention in most of the Campus’ winter cereals. This will be addressed this month. The range of cleaver herbicides has expanded in recent years. Where conditions are warm and weeds are actively growing, Starane will provide effective control. In colder weather, or where a wider weed control spectrum is required, alternatives (for example, Boxer, Chekker, Eagle, Lotus, Platform S or Starane XL) should be considered.

Recent DARD weed surveys suggest that wild oats are becoming a problem on many farms. Where inspections indicate that wild oat infestations exceed rogueable levels, specific herbicides should be used: Avenge 2, Cheetah Super, Corniche, Grasp, Tigress Ultra or Topik in wheat crops; Avenge 2, Corniche, Grasp or Tigress Ultra in barley crops. Consult product labels for latest timings.

Rhynchosporium in barley and Septoria tritici in wheat are the two main disease threats for these crops.

Winter barley should be sprayed at GS31 (first node detectable) with a mixture containing, a robust rate of triazole and a strobilurin in crops with higher yield potential. Suitable options include: Acanto + Opus or Punch C; Twist + Opus, Punch C or Landmark. Where symptoms of mildew are found, the inclusion of a morpholine such as Corbel in the tank mix is suggested.

Winter wheat should receive its first fungicide spray as soon as leaf three has emerged. This normally coincides with GS32 (second node detectable). A triazole (for example, Opus, Foil or Flamenco) should be the linchpin of this spray.

Early sown crops are likely to have a relatively long interval between their first and second fungicide treatments. In this situation the persistence of the first spray can be improved by the addition of chlorothalonil (for example, Bravo). With Septoria tritici resistance to strobilurin fungicides now widespread, their use is restricted to two applications per crop. If the crop is being cut early for wholecrop or crimping, or where Take-all is being targeted with Amistar then the strobilurin can be included in the first spray along with the triazole. For later harvested crops especially for seed or milling it is best to leave the two-strobilurin applications until the later timings at flag leaf and ear fully emerged, again in a mixture with a triazole. If mildew is visible on the older leaves products containing fenpropodin or quinoxyfen will prevent spread to new growth.

The early sown winter wheat crops at Greenmount are approaching GS 31 and will receive a T1 fungicide of Opus (0.5l/ha) + Comet (0.7l/ha) in accordance with the above measure to reduce Septoria resistance.

Paying close attention to seed spacing can make significant improvements in marketable yield. Seed spacing should be adjusted according to variety, seed size, end market and seed cost. Seed should be ordered as split graded, in the size bands 35mm-45mm and 45mm-55mm. Closely graded seed will result in a more even crop and will help in achieving maximum marketable yield in the desired size range. Once planting has started, check seed spacing by uncovering the drills and measuring the actual spacing using a tape measure. Checking that planters are in good repair and properly calibrated before use will help to ensure good placement of seed.

Wait until ground conditions are suitable before cultivating. Compaction caused by ‘forcing’ a seed bed in poor conditions restricts root growth, leaving the crop susceptible to nutrient deficiencies, drought and lower yields. Aim to produce a fine tilth that retains moisture and assists the performance of residual herbicides.

Results from the hot box testing of home saved seed at Greenmount Campus has shown that many seed crops are heavily infected with silver scurf and to a lesser extent black scurf. Where seed has not been fungicide treated prior to delivery, growers are urged to wash a random sample of 50 tubers per seed lot and estimate the levels of both diseases. Where black scurf is present on any tubers or where silver scurf is evident on 5% of tubers a seed treatment will be beneficial.

Certified seed potatoes of the crisping varieties Lady Rosetta and Lady Claire have been delivered to Greenmount Campus. At present the seed is being held in cold storage at 4ºC to prevent excessive sprout growth. Planting will be delayed until soil temperatures reach 10oC.

DARD Farm Management Notes for April 2004 have been prepared by Greenmount Campus, College of Agriculture, Food and Rural Enterprise - Tel: 028 9442 6771.