Fertilisers, Spreaders & Applicators
Low pH will compromise yield and quality The October 2018 report on nutrient management planning and practices for the Professional Nutrient Management Group (PNMG) concluded that the use of lime could be improved, says British Sugar. The report stated that lime use has decreased steadily and in 2016/17 the amount applied was around half the estimated annual loss from soils of 4.25mt CaCO3. In fact, the use of liming materials in Great Britain has decreased over the past two decades at an average rate of around 86,000t/year, to just over 2mt. Furthermore, data collected via the 2017 PAAG survey showed that 53 per cent of grassland and 16 per cent of arable land soil samples tested at, or below pH 6.0. The five year average data from the British Survey of Fertiliser Practice (BSFP) demonstrates continued low levels of liming in both arable and grassland rotations, as shown in Table 1.
Quality standard Launched by ALA, the Aglime Quality Standard exists to provide farmers and advisers with product quality information for participating suppliers. Be aware that not all ag-lime materials meet the required standards, points out British Sugar. To be sure, the company says that growers should ask for more than just the neutralising value (NV) – it is vital that you know what per
centage passes the 150 micron sieve, and what the reactivity performance level is. A quality lime should have at least 40 per cent passing 150 micron, with at least 70 per cent reactivity. NV combined with fineness drives the reactivity and, with it, rate and extent of pH change and potential longevity. According to British Sugar, LimeX offers an unrivalled minimum 85 per cent passing 150 micron sieve and 95 per cent reactivity. This delivers fast but lasting pH correction in arable and grassland rotations and may be used in organic farming systems. The integral nutrient package within LimeX contributes to maintaining soil fertility and increases available calcium. A ‘maintenance’ application of LimeX70 at 7.5/t ha will also supply a minimum of: • 75kg P2O5 • 50kg MgO • 45kg SO3 (typically worth c.£80/ha) LimeX meets all quality criteria of the Aglime Quality Standard, and is available to order now for summer and autumn 2019. British Sugar says that following major investment, the Cantley factory, Norfolk is pleased to offer LimeX70 from the start of the 2019/20 campaign, joining Bury St Edmunds, Newark and Wissington in the nationwide supply of over 300,000t of LimeX per annum.
Table 1: BSFP survey data showing average national lime use by rotation (% of land). Year
2013 2014 2015 2016 2017 5yr avg
All tillage
7.4
8.7
8.0
6.4
8.4
7.8
All grass
3.0
4.0
3.1
3.2
2.9
3.2
The 5-year averages are equivalent to liming grassland on a 31-year cycle and arable land on a 13-year cycle – however, this will not sustain pH or yield and profitability, says British Sugar.
Table 2: The impact of low pH on macronutrient efficiency. Nutrient efficiency (utilisation) Soil pH
N
P
K
4.5
30%
23%
33%
5.0
53%
34%
52%
5.5
77%
48%
77%
6.0
89%
52%
100%
7.0
100%
100%
100%
Source: Efficient Fertiliser Use Manual – pH
Routine rotational soil pH testing is required to ensure an effective liming policy is in place to avoid consequential loss of yield and quality by maintaining pH at an appropriate level for the rotation.
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