10 May 1996


What fertiliser you put on your silage land makes a big difference to yields and quality, as SAC research found


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DAILY intake and liveweight gain of heifers fed silage fertilised with a granular fertiliser is greater than that of heifers fed silage fertilised with a blend or straight nitrogen.

That was the result of a Scottish Agricultural College trial carried out during the 1995 first-cut silage season on behalf of Kemira Fertilisers.

The trial aimed to compare the effects of fertilisers on grass yields, grass and silage quality, and the dry matter intake and liveweight performance of dairy heifers.

Treatment included comparisons of a 20.8.12 granular fertiliser (Kemira Premier Cut), a 20.6.12 blended fertiliser, straight nitrogen and nitrogen with slurry. In each case the total nitrogen applied was 125kg/ha of nitrogen (100 units/acre).

Treatments were applied on 2-year-old sward in 0.4ha (1-acre) plots on March 21. This was to achieve applications at least eight weeks before cutting for silage on May 23. No additive was used.

The granular fertiliser silage produced over 0.5t/ha (1.2t/acre) extra of silage dry matter, an increase in yield of 155, says Kemira.

Finished silages were fed to livestock for six weeks (see table). The silages were offered with a 1kg a head a day supplement of a barley/soya/mineral mix to youngstock (initial liveweight 157kg). There were five heifers a treatment and the feeding trial lasted for six weeks.

Results showed that while straight N fertilisers in spring may provide for good grass growth, the resultant silage may not be as good in quality as when blended or granular products are used. The granular 20.8.12 provided silage that produced the highest intakes and liveweight of heifers.

It achieved a 27% increase in liveweight a hectare over the six-week period compared with those fed on silage produced by the blended fertiliser (NB this is an unreplicated trial).n

Average silage dry matter intakes and liveweight gain of heifers

Fertiliser typeNN + slurry20.6.1220.8.12

BlendPremier Cut

Herbage yield (kg DM/ha)

Intake (kg DM/day)3.473.604.164.35

Liveweight gain (kg/day)0.550.580.630.73

SAC trials carried out in 1995 compared the effects of different fertilisers on grass yields, grass and silage quality, DM intake and heifer performance.