With fertiliser price once again moving, it is important to remember the value of your organic manures, and balance your fertiliser application accordingly.
Making the most from what you already have…
The Nitrogen, Phosphate and Potash in an average 5 tonne application of Farm Yard Manure is worth £32.37p at today’s fertiliser prices, and a 2000 gallons application of 6% slurry equates to £27.32p.
This makes the muck heap and lagoon two of the best assets on the farm.
Organic manures are a rich source of nutrients, but the ratio of the nutrient content isn’t balanced, especially where sheep and cattle are concerned.
If we look at the table again we can see that for FYM at 5 tonnes an acre we are applying
6:32:79 units which gives us a N:P:K ratio of roughly 1 : 5 : 13 (for a fertiliser like 20.10.10 this would be 2:1:1), and for slurry 1: 1.3 : 3.6.
If we exclude the nitrogen we can see that in both cases ever unit of P we are apply we are applying roughly 2.5 units of K. So targeting organic manures to crops and soils which will benefit from potash applications is vital (silage ground and low K index soils). By doing this, we can start to reduce fertiliser costs and/or improve quantity and quality of grass production.
Consistent over application to the same fields over time will increase soil reserves, but with this comes potential problems such as staggers risks and dry cow problems.
The other thing here to consider is replacement cost. For example, grazing grounds on K index of 2 has no requirement for extra Potash, due to the recycling of nutrients of the animals grazing it.
Conversely Silage grounds with a K index of 2 still have a large potash requirement. If we look a the values of potash in the table above every 5t of FYM we apply to grazing ground at a K index 2 we are applying £18 (£12 for 2000 gallon of slurry) of potash that isn’t needed, and could be applied to silage ground.