Many spring cereal crops may have received nitrogen (N) already, but there are plenty of crops which were only planted last week or the week before which will need attention in the coming days.

Crops are emerging fast and it is ideal to apply nitrogen once the tramlines have emerged.

It is important to keep an eye on nitrogen rates and not to exceed limits. All farms should have a nutrient management plan.

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Applications

Nitrogen applications are based on previous crop and previous yields and growers should also take into account cover crops and their uptake.

Some might choose to cut back nitrogen rates slightly, as the cover crop should have taken up nitrogen from the soil.

The nitrogen index system should be followed for applications. Table 1 shows the allowances for each index.

Index 1 applies to fields in continuous cereals or where the previous year’s crop was maize. Index 2 includes crops after oilseed rape, protein, potatoes, beet and one- to four-year grass leys.

Crops straight out of permanent grass which was grazed fall into index 4. Crops two years out of permanent pasture or in the first year out of permanent pasture which was cut only fall into index 3.

A field in its third or fourth year out of permanent pasture, which was grazed only, falls into index 2. A field two years out of permanent pasture which was cut only falls into index 2.

A field in its fifth year out of permanent pasture which was grazed only fits into index 1. A field which is three or four years out of permanent pasture and was cut only falls into index 1.

See table 1 for the nitrogen allowance in each of these indices.

Higher rates

Higher nitrogen rates can be used where the farmer has data from any of the past three harvests showing yields above reference yields, based on grain at 20% moisture content.

For each tonne above 6.5t/ha for spring barley and oats and 7.5t/ha for spring wheat, an extra 20kg of N/ha can be applied to crops.