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Planning for the 2021 grazing season: Tips on creating a nutrient management plan
Producers looking to plan and prepare for the next grazing season could benefit from a nutrient management plan, says Siwan Howatson, grass and forage scientist at AHDB.
As many are likely to be tight on forage, it will be important to promote grass growth as early as possible.
Checking soil test results are up to date and reviewing grass growth for 2020 will help plan the use of nutrients for the coming season.
Sampling
Ms Howatson suggests soil should be sampled and analysed every three to five years and says sampling 25 per cent of fields each year is an efficient way of maintaining this schedule.
She says: “If your soil test results are more than four years old, then plan to take new samples.
“When taking samples, try to collect them from the same point in the season. Your soil test results provide
essential information on phosphate, potash, magnesium and, crucially, pH.
“Lime is often overlooked, yet is arguably the most critical factor to improve grassland productivity.
“The target pH for optimal grass growth is between 6 and 6.5. It is important to correct soil acidity, otherwise grassland productivity can be affected dramatically.”
Lime can be applied when ground conditions allow. However, if silage is to be grown, lime should be applied two to three weeks before the first spring nitrogen application.
“If you are satisfied with your soil test results, the next question is how well, or not, grass grew this season, as phosphate and potash applications should be adjusted where yields were lower than expected.
“The AHDB Nutrient Management Guide (RB209) provides typical offtake values for fresh grass and silage that can be used to adjust application rates if actual figures are not available.
“For example, if the first cut of silage was 5 tonnes less than expected, you should make allowance for this.
“At 25 per cent dry matter, you would have expected 5t fresh weight
of silage to take up and remove approximately 10kg P2O5/ha.
“Therefore, the total amount you planned to apply should be reduced, taking in to account lower yields across the whole season if necessary.
“Large applications of phosphate and potash should be avoided, and smaller applications spread during
the season.
“If you use a compound, be sure to choose one that has the most suitable ratio of nitrogen, phosphate and potash.”
Cost saving
Grazed grass and home-grown forage can be the cheapest form of feed when well-managed and have the potential to reduce the costs of bought-in feed significantly, says Ms Howatson.
“The return on investment for fertiliser nitrogen compared with bought-in nitrogen in the form of high-protein supplementary feeds in the winter is at least 3:1,” she says.
“However, too much nitrogen produces grass with low sugar levels and any resulting silage can have high ammonia and butyric acid levels, making it less palatable.
“Nitrogen is also a so-called ‘mobile’ element and can be leached out of the soil and reduce water quality in your catchment.
“As always, it is crucial to account for the phosphate and potash supplied by applications of manures when
planning manufactured fertiliser applications.
“Applying slurry to silage ground, or to a proportion of the first grazing round covers permitting, will allow considerable cost savings to be made.”
In the field: John Haimes, Devon
Devon farmer John Haimes carried out a soil nutrient management plan as part of the AHDB Strategic Farm programme.
He says: “When we did a soil chemical test, the analysis showed that 10 out of the 14 fields were acidic, the lowest being 5.2pH.
“We have been trying to rectify this since by applying lime at 2.5t/ha.
“We also applied farmyard manure at 10t/ha across the fields identified low in potash to bring indexes back to the optimum index of 2-.”
Mr Haimes is aiming to increase soil biology and organic matter and by growing various forage mixtures.
The soil structure has improved because the plants have different routing depths, with the red clover and chicory growing deep within the soil.
“We have seen an increase in the number of worms and worm casts and we are hoping that the soil will be become more resilient and more drought tolerant, which means more grass growth and will allow more animals to be kept which results in a more profitable system,” he says.
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