Crop Notes March 2010
Cereal management
Winter cereal management
With improving ground conditions all growers should complete Phosphorus (P) and Potassium (K) fertiliser applications to previously untreated crops to meet crop requirements. Where needed, apply grass weed herbicides to later sown crops.
Fertiliser nitrogen rate
More advanced crops of winter barley can utilise the first split of the Nitrogen (N) top dressing. The total amount of N applied is more important than timing. Crop type, soil type, previous crop and any slurry or farmyard manure applications prior to sowing N should all be taken into account when deciding on the optimum rate. Urea or Calcium Ammonia Nitrate (CAN) are equally effective for the first top dressing. If the crops P and K requirement has already been met there is no need to apply a compound (NPK) fertiliser.
Application timing
Fertiliser N applications to winter crops in the spring should be based on crop growth stage. Barley starts growing earlier in the spring than wheat and should receive priority whenever planning top-dressing programmes (see table below). While this is the general rule, growers of second or third wheat’s that are more susceptible to take-all should note that it has been shown that these crops benefit from an earlier first N application.
Recommended fertiliser N top dressing timings for winter cereals
| Typical calendar dates | Typical calendar dates | ||
|---|---|---|---|
| Proportion of total N top dressing | Growth stage | Winter barley | Winter wheat |
| 1/3 | Late tillering (GS 27-29) | Late Feb/early March | Mid/late March |
| 2/3 | First node detectable (GS 31) | Early/mid-April | Late April/early May |
Disease control
Mildew and Rhychosporium are the diseases most likely to be present in winter barley during March. Only where these diseases are at a high level and are actively invading the new growth would a fungicide be economically justified before GS 30-31 (T1 timing). If disease levels require early spraying T0, use a reduced rate of an appropriate fungicide and follow up with a full rate spray at T1.
Spring barley sowing
Early establishment is vital for high yields. Aim to sow as soon as ground conditions allow, bearing in mind the following:
- select a variety that best suits your farm and management system from the Recommended Cereal Variety Booklet for 2010.
- ensure the soil pH status is sufficiently high before you sow. There may still be time to carry out a soil analysis if you move quickly.
- seed rate should be based on thousand-grain weight. Aim for between 350 – 400 seeds per square metre for March sowing.
Drilling spring barley
Potato management
Sprouting
Where it is the intention to sprout maincrop seed potatoes, these should be set up as soon as possible. A number of systems are available for sprouting, including tray and bag systems. It is important that chitting houses provide:
- temperature control and ventilation (to control sprout growth and protect against frost)
- light (to control sprout growth)
Physiological age measures the degree of ‘ageing’, which is given to seed during sprouting and is determined by the cumulative number of degrees of temperature above 4oC following dormancy break. For example - seed stored at an average of 10oC for 10 days will have accumulated 60 day degrees of physiological age. In practice, a maximum/minimum thermometer is used to record the average temperature in the chitting store on a daily basis.
The aim in sprouting late maincrop varieties such as Navan is 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 to sprout in a chitting house on 1 March, providing an average of 6oC per day, would accumulate 264 day degrees, that is, 44 days x (10oC – 4oC).
Seed potatoes
