Given the recent hike in fertiliser prices, there has never been a more pressing need to investigate your soil’s nutrient status for better targeted use of organic manures and to save on expensive fertiliser costs.
Soil sampling should be carried out every four to five years and can be done at any time of year, but samples are best taken in the Autumn or Winter. For the most accurate results, soil testing should take place at least three months after the last application of slurry, FYM, fertiliser and two years from when lime was last applied. It is important that soils are not overly dry or waterlogged at the time of sampling.
Standard soil analyses will provide results on pH, lime requirement, and extractable P, K and Mg. Analysis for sulphur is also worth looking at, especially when you consider its essential role in the production of amino acids, the building blocks for protein that is required for plant development and growth. A sulphur deficiency will reduce nitrogen uptake, therefore affecting yield. If sulphur status is low, it should be corrected to make the most efficient use of applied N.
The importance of correcting soil pH should not be underestimated and is crucial for grass growth. The difference between a pH of 5.5 and 6.5 could be as much as 40% more grass yield. Now is the best time to correct soil pH and apply lime before conditions get too wet and to allow time for it to penetrate into the soil and raise the pH in preparation for the next grass season. Liming to achieve the optimum pH will enhance the availability of nutrients to the growing crop. Aim for pH 5.9 to 6.2 for grassland and towards the upper end of this range for clover rich swards, and pH 6.3 for arable. Liming instead of fertilising extensive grazing ground may actually be a better investment, especially if soil pH is below the desirable level.
Livestock manures have never been so valuable. Typical figures for dry matter and the nutrient content of various manures are available in the following technical note: https://www.fas.scot/downloads/technical-note-tn736-optimising-application-livestock-farmyard-manures-slurries/
However, it is worth getting your organic manures analysed to know exactly what you are applying to minimise purchased fertiliser requirements. The cost is around £49/sample to test for dry matter, N and several minerals including P and K.
Tips for dealing with high fertiliser prices:
- Soil sample if this has not been done in the last four to five years.
- Correct lime status now!
- Analyse slurry, FYM, digestate and other organic manures to be applied. Draw up a plan for strategic use of these valuable inputs and calculate purchased fertiliser requirements to meet the requirements and the offtakes of the crop.
- Depending on the soil analysis, could you take a P &K holiday?
- Do a forage budget. If you are in a good position with carryover forage stocks likely into next summer, can you afford to purchase less N fertiliser on silage ground and accept lower yields?
- Closely monitor grass fields in the spring and measure growth with a plate meter so that poorer performing fields can be identified, allowing fertiliser applications to be targeted to areas of greatest need.
- Longer-term, consider the use of more clover in the sward and particularly red clover in silage fields, which can fix more nitrogen than white clover (up to 250kgN/ha in its first full year compared to 180kg N/ha for white clover at an inclusion rate of 3 to 5kg/ha). Look at organic principles.
- Investigate sources of alternative fertilisers e.g. distillery washings, compost, etc.
While the current cost of buying in fertiliser will be making farmers question their usual requirements and whether they can get away with less, it could end up being false economy if you need to buy in silage next winter. For the vast majority, you cannot afford not to spread fertiliser but there are steps that can be taken to help cut usage and target applications where they are needed most.
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