P and K can be maintained by putting all the slurry in silage area

This has been an exceptional year providing an unusually good opportunity to spread slurry as soon as the closed season ended in mid-January.

Teagasc researchers put a value of up to €28 per 1,000 gallons on undiluted slurry.

About 85% of the value comes from the P and K, but if slurry is spread in the spring, much of the N (worth €5 per 1,000 gallons) can be utilized.

In order to make the best use of slurry, and to cut fertiliser costs, it is absolutely essential to know the P, K and lime status of each separate area of your farm.

The P and K in slurry are almost 100% available to grass in normal soils.

Once the P and K levels are brought up to standard (based on a soil test), P and K levels can be maintained by applying all the slurry in the silage areas.

The availability of slurry nitrogen varies widely according to factors such as timing and methods of application.

About half the slurry nitrogen is in organic form, and is not available to crops in the year of application, but can be released gradually over time.

The other half is in the form of ammonium which is readily available to crops, under certain circumstances.

By spreading slurry in early spring with traditional methods, it is estimated that 25% of the N can be utilised, but only 5% is available if it is spread in the summer because it generally goes away in the air, in dry summer conditions.

Newer developments in spreading techniques such as the trailing shoe or band spreading or the dribble bar increase availability further.

The target should be to apply at least 75% of slurry in the spring before closing up for silage, and the remainder before mid-June, in cool moist conditions if possible.

This can significantly cut the cost of fertiliser N for silage.

Diluting slurry with water makes its nutrients more available to grass. It is advised not to graze for six weeks after slurry, and not to apply nitrogen fertiliser within 7 to 10 days of slurry.

Lime should be well washed into the soil before slurry is applied.


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