Crops Notes February 2007

CROPS

Winter wheat crops sown early have established well with good plant counts. Later sown crops in many areas are under stress and suffering from water logging. The first assessment necessary before any management decisions are made, is a plant count to establish the number of viable plants.

Using a 0.5-m stick, walk a “W” path through the field. Stop at two places along each side of the “W” to do a plant/shoot count so that counts are completed in a total of eight places in the crop Throw the 0.5 m stick a short distance into the crop. Wherever it lands align the stick so that it runs parallel between two rows of plants.
Count the number of plants/shoots along both sides of the stick. This gives the number of plants/shoots per m at that point in the field.
The distance between rows must be measured before plants/m² can be calculated. This should be done several times and the average calculated. (Normally 12cm)
Calculate the average number of plants/shoots per m using the formula:

Average plants/shoots per m =

total number of plants counted in 8 places in field

Calculate the plant/shoot population (plants/shoots per m²) using the formula:

Plant/shoot population

(Plants/shoots per m²) = average plants/shoots per m x 100

the distance between rows (in cm)

If the plant population is below 30 plants/m² plough the crop down and resow with a spring cereal crop. This option should be seriously considered particularly if the crop was late sown, the plants are unevenly distributed in the field or if the crop has suffered from soil structural problems that are likely to be remedied by ploughing, for example, surface capping.

If the plant population is above 30 plants/m² and the plants are fairly evenly distributed and there are no obvious soil structural problems the crop may still yield well even at such a low population, particularly if sown early.

If a crop is thin nitrogen at 40 KG/ha applied at early tillering, will encourage tillering and is certainly less costly than resowing with a spring barley crop. Provided weather improves, shoots produced now may give a satisfactory return compared to the cost of resowing.

Winter barley

Monitor early sown crops and where a T0 (GS 30) fungicide would prevent early disease building up and offer some insurance against a delayed T1 (GS 31-32) fungicide application, this should be applied. Growers should continue to monitor crops for signs of slug or leather jacket damage and treat if necessary. Where autumn herbicides have not been applied every effort should be made to apply them as soon as possible, ground conditions permitting, before the weeds get too large.

Spring cereals

The new Recommended List for Northern Ireland will be available in early February from your local County Development Centre or is available now on the AFBIni web site, http://www.afbini.gov.uk/index/services/specialist-advice/recommended-varieties-lists.htm

There is often a shortage of seed for new varieties, so remember to order early.

Potatoes

Seed preparation for planting

As seed potatoes arrive on farm, growers are urged to have a sample hot boxed to determine the presence of diseases and overall sprouting vigour. Results from hot box testing at Greenmount on home saved seed have shown that the skin blemishing diseases silver scurf and black scurf are prevalent on almost all seed samples if these diseases are present 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, that is, 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 four to eight 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 10^oC, would accumulate 264 day degrees, that is, 44 days x (10^oC - 4^oC).