Crops notes March 04

Winter wheat crops will receive their first nitrogen dressings this month. We will apply 40 kg/ha of nitrogen. Thicker crops, those with more than 1000 shoots per square metre, will not be treated until the start of stem extension. Sulphur will be applied along with the nitrogen since sulphur deposition is thought to be low in Northern Ireland soils.

Spring barley seed of the varieties Static and Kirsty have been ordered.

The new DARD/HGCA Recommended Cereal Varieties booklet is now available from your local DARD Development Centre and Crops Development Advisers.

The key determinant of spring barley yield is sowing date. Local research found that one month’s delay in sowing often led to a yield reduction of around 2 t/ha. Sowing should take place as soon as a good seedbed can be created. The chosen seed rate, calculated from the thousand-grain weight, should lie between 350 and 400 grains per m2. The lower rate should be suffice for March-sown barley drilled into a good seedbed. In poorer conditions, or if sowing later, the higher rate is preferable. Remember that spring barley is very sensitive to pH and a soil test should be carried out if there is any doubt.

Normally one third of the total nitrogen (N) top dressing should be applied during late tillering (late February/early March in winter barley, mid/late March in winter wheat) and the remainder applied during early stem extension, Growth Stage (GS) 30-32, which for winter barley is reached in early/mid April and by winter wheat in late April/early May. Due to ideal sowing conditions in the autumn many winter cereal crops have established well producing crops with high plant numbers. Thick wheat crops, those with more than 1000 shoots/m2, however, are at increased risk of lodging later in the season and nitrogen top dressings should be delayed till after GS 30.

Crops at risk from take-all, for example second wheats on light land, may benefit from a little extra nitrogen at late tillering.

Since 1985 atmospheric deposition of sulphur (S) has fallen by more than 25% in Northern Ireland. Consequently DARD scientists estimate that approximately 50% of our soils are now deficient in sulphur. Risk of deficiency is highest where soils are light and rainfall is low. Winter cereals should receive 20 kg S /ha (50 kg SO3 /ha) in the spring before GS 32. This is most conveniently applied as ammonium sulphate which will also add nitrogen.

Attention to detail during the handling and preparation of seed prior to planting can result in an increased early tuber yield, while optimising fry colour and skin quality.

As seed arrives on farm, growers are urged to have a sample hot boxed to determine the presences of diseases and overall sprouting vigour. Results from hot box testing at Greenmount have shown that the skin blemishing diseases silver scurf and black scurf are prevalent on almost all seed samples. Seed should be treated with a fungicide pre-planting with the aim of reducing disease transmission and maximizing marketable yield. Germination or sprouting ability of all seed lots has been good, indeed with the relatively mild winter conditions, management of sprout growth will be essential to ensure short, strong green sprouts are produced.

A number of systems are available for pre-sprouting including tray and bag systems. Systems must ensure adequate temperature control and ventilation (to control sprout growth and protect against frost) and light (to control sprout growth).

Seed of early potato varieties should be set up in sprouting boxes with the aim of promoting apical dominance i.e. producing one strong sprout per seed tuber, one stem and a small number of large tubers early. The opposite holds for maincrop potatoes where multiple sprouting is encouraged to produce many tubers which can increase in size over a longer growing season.

Maincrop seed potatoes should be set up to sprout 4-8 weeks prior to planting depending on variety and target market.

The aim in pre-sprouting late maincrop varieties such as Navan would be to accumulate 250-300 day degrees prior to planting. Working back from a target planting date of say 20 April, and allowing seven days for dormancy to break, seed set up on 1 March assuming an average daily temperature of 10oC, would accumulate 264 day degrees, that is, 44 days x (10oC - 4oC).

This system of seed preparation aims to produce seed tubers with sprouts no more than 2 mm long. Seed is stored at 3-4oC until close to planting time. The refrigeration unit is then turned off for 7-10 days to allow chitting to occur.

Once sprouts of 1-2 mm have formed evenly, the seed should be cooled down again to 3-4oC to prevent further sprout growth up to planting. Mini-chitting, whilst not having the benefits of earlier harvesting associated with pre-sprouted seed, produces a crop that emerges quickly and evenly.

Establishing the soil nutrient status is fundamental to providing the potato crop with optimum fertiliser application either from artificial fertilisers or slurry/farm yard manure. Immediate attention to this will enable results to be obtained, requirements to be determined, orders placed and the product on hand when required at planting.

DARD Farm Management Notes for March 2004 have been prepared by Greenmount Campus, College of Agriculture, Food and Rural Enterprise - Tel: 028 9442 6771. We acknowledge the contribution from Veterinary Service. For further information contact your local Development Adviser.