The recent burst of grass growth has seen many farmers removing surplus grass as bales, but it is important to remember to replace the nutrients that have been removed by making these bales.
While making extra bales this year may help alleviate the reduced yield experienced by many when harvesting first cut silage – be aware of the amount of phosphorus (P) and potash (K) they remove from the paddock.
Bales are also the most practical way of maintaining grass quality and ensuring the best feed is available for grazing.
Replacing nutrients after making bales
Once bales have been removed from a paddock, it is important that the nutrients removed are replaced. A bale of silage weighing 800kg fresh [200kg Dry matter (DM)] has removed 1.6 units of P and 10 units of K from the paddock.
So the removal of four to five bales/ac will mean that between six and eight units of P/ac and 40-50 units of K/ac are required.
This is important, as a rough rule of thumb is that 50 units K/ac is enough to change a soil K index – which means a paddock/field could go from index two to index three or vice versa.
If there is no slurry and only straight nitrogen (N) is applied before and after cutting the surplus bales, there will be a large shortage of P and K in this paddock.
When completing soil testing, many farmers have discovered the soil’s K indexes to be low on individual paddocks – these paddocks often had surplus bales removed regularly and the removed K was not replenished.
When removing surplus grass as bales it is important to remember that three to four bales/ac requires 1,000gal of thick slurry or 2,000gal of watery slurry to replace the P and K removed.
Where you have no P allowance and no slurry is available, it is recommended to spread a compound like 29:0:15+S.