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30Nov

Side dressing cereals for optimum yield

THIS PROMOTIONAL FEATURE WAS PROVIDED BY BALLANCE AGRI-NUTRIENTS.

Side dressings, particularly of nitrogen (N), at key growth stages will optimise cereal crops such as wheat and barley, lifting yield and protein content.

Cereals are a depletive crop, removing large amounts of nutrients, especially N (see Figure 1). High yielding crops remove more nutrients, and the type of crop residue and how it’s managed will impact nutrient levels in the soil.

Nitrogen is one of the most important factors for achieving a desired crop yield and, in the right amounts at the right time, improves tillering and stem elongation and keeps leaves green, resulting in higher yields and protein content.

Figure 1 Nutrient uptake for cereals

Nutrient

Nutrient uptake
(kg nutrient/T grain)*

Nitrogen

25

Phosphorus

3

Potassium

15

Sulphur

2

*includes nutrient uptake by straw

Nitrogen requirements 

Nitrogen requirements depend on desired yield, soil N content and end use. A rule of thumb to calculate cereal N requirements is 25 kg N/ha per tonne of yield, using the formula:

Fertiliser N (kg N/ha) = (25 kg N x expected yield (T/ha)) – Mineral N (kg N/ha)

Barley grows fast, but generally needs less N than wheat, particularly if grown for malting. As N can increase the grain’s protein content, malting barley needs less N in order to keep the protein content within an appropriate range. Barley does however have similar sulphur (S) requirements to wheat.

When to apply 

The timing of N fertiliser is important for cereal crops: application should coincide with rapid growth periods, such as stem elongation for wheat, and tillering for barley.

For both crops, a Mineral N (or deep N) test at stem elongation will help to refine fertiliser N inputs. It determines readily available forms of N in the soil, which go towards meeting the crop’s N requirements.

Two-thirds of wheat’s total N requirement should be applied at Zadoks growth stage (GS) 30/31. If large amounts of N are needed, the applications are best split between GS 30/31 and GS 32. The remaining third is applied at GS 39.

Barley needs a third to half of its N requirements at sowing, and the remainder at tillering (GS 20-29). This encourages early tillering, leading to strong growth and early canopy cover, and limited potential for secondary tillers later.

For both wheat and barley, S is usually applied at sowing, and 15-25 kg S/ha/year generally satisfies requirements. However, if S leaches over winter for autumn sown wheat, plant available sulphate S should also be applied in spring with the first N side dressing.

Useful products for wheat and barley side dressing

For N-only side dressings, SustaiN is the preferred product to use when 5-10 mm of rain is not likely to fall (or irrigation is not possible) in the 8 hours after application. SustaiN is urea coated with Agrotain, an N stabiliser that reduces N loss volatilisation by on average, around 50 per cent compared to standard urea1. This means more N is retained in the soil for use by the crop.

If other nutrients are required in the side dressing, good options are Advantage SOA, containing both S and N, or YaraMila Actyva S, which also includes potassium, phosphorus and magnesium, and the micronutrients boron, manganese, and zinc to provide additional support. It is ideal for side dressing cereals and has been tested to spread up to 32 m in a well-calibrated spreader.

Both Advantage SOA and YaraMila Actyva S are compound fertilisers, and consist of even granules, manufactured to be as uniform as possible in terms of shape, size and weight. Each granule contains a specific ratio of nutrients, so nutrients are applied more evenly, promoting even growth, and reducing the risk of striping. Not all compounds are equal, with manufacturing, transport and handling impacting their product quality. Bagged compound fertilisers, such as YaraMila products, have decreased handling (improving granule uniformity) and a higher granule strength (decreasing risk of shattering at high spinner speeds).

1 Zaman M, Saggar S, Stafford AD 2013. Mitigation of ammonia losses from urea applied to a pastoral system: The effect of nBTPT and timing and amount of irrigation. Proceedings of the New Zealand Grassland Association 75: 209-214

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