Fertiliser spreaders are starting to roll around the country again as better weather promotes drying conditions and grass growth. It’s important that these crops get the nutrients they need in the right amounts to maximise yields. Nitrogen is obviously vital.

The guidelines in table 1 are based on a minimum of 50 days between spreading and cutting. Younger grass swards rich in perennial ryegrass will have a demand for nitrogen up to 25% higher than older swards (>5 years).

Pages 10-11 discusses the options for farmers in a dilemma currently about ungrazed, unfertilised silage ground. One of these options may be to fertilise ground with a reduced rate of nitrogen, while still maintaining a planned cutting date in late-May. This is only required if we are giving the fertiliser less than one day for every two units applied to work into the plant. Otherwise we can go as normal.

Silage is a very hungry crop from a P and K point of view and the table also outlines guidelines for these.

Do not under estimate the value of your cattle slurry, or indeed imported pig slurry as a source of nutrients. Table 2 puts values as sources of N, P and K on cattle slurry based on dry matter percentage, and pig slurry. Use it in conjunction with Table 1 to work out how much synthetic fertiliser can be reduced. If we are using slurry, we need to get it out ASAP to give it time to work into the soil. Following this, allow one week between slurry and fertiliser top ups.

Splitting the volumes

In terms of spreading now, splitting the big volumes of nitrogen we are using will reduce any potential N losses we could encounter, particularly on heavy ground or during wet weather. However, if conditions allow, there is no issue spreading all at once.

Leave two weeks between applications for best results. CAN is generally the N-source for silage ground. This is because it is more stable in warmer, settled conditions. However, the conditions we’re experienced in recent weeks have been anything but warm and settled, and remain so in places. Urea is a viable alternative here – it will be more stable than CAN in times of wet weather.

On lighter or low organic matter soils, sulfur deficiency can be a problem. Most N-fertilisers can be bought with Sulfur included and it’s an important compound from the point of view of maximising both silage yield and efficiency of nitrogen usage. A rate of around 20kg sulfur/ha is recommended.

Read more

Silage 2018 – what what can you do to get back on track?

Making the most of current fodder reserves