The Importance of Sulphur Fertilisation for Crops
In the past, much of the sulphur required by plants was obtained through sulphur deposition from the air. However, due to the desulphurisation of flue gases from industry, this deposition has steadily decreased. Today, there are risks of sulphur deficiencies in crops, making sulphur fertilisation necessary to prevent these deficiencies.
Crops do not all have the same sulphur requirements. Cruciferous crops, such as cabbage and rapeseed, have high sulphur needs. Grasslands also require high levels of sulphur (S). For these crops, there is often a need early in the year and/or during a short period when the crop’s sulphur requirement is high.
The sulphur requirement of arable and vegetable crops has been classified into four categories:
- Very high requirement: 50-60 kg S for Brussels sprouts and head cabbage;
- High requirement: 40-50 kg S for cauliflower, Chinese cabbage, celeriac, and cabbage;
- Moderate requirement: 20-30 kg S for ware and starch potatoes, kale, broccoli, cereals, grass seed, carrots, peas, runner beans, leeks, silage corn, and onions;
- Low requirement: 15-20 kg S for seed potatoes, lettuce, sugar beet, and flax.
Sulphur Sources for the Plant
Plants have access to a diverse range of sulphur sources, including S-min (soil stock of mineral sulphur), deposition (sulphur from precipitation), capillary uplift (sulphate from groundwater), irrigation (as irrigation water can contain sulphate), and soil sulphur yield, where sulphur is released through the decomposition of organic matter.
Sulphur in the Soil
The soil’s sulphur yielding capacity requires some additional explanation. Sulphur is released through the mineralisation of soil organic matter, which requires appropriate soil temperature and moisture levels. Most mineralisation occurs in the second half of the year when the soil temperature is adequate, and soil life is active. Plants that require a significant amount of sulphur early in the spring, such as cereals and grasses, do not receive enough sulphur from mineralisation at that time and may benefit from sulphur fertilisation.
Sulphur Fertilisation for crops
Not every sulphur compound is absorbable by plants; they absorb sulphur (S) in the form of sulphate (SO4^2-). It is important to consider this when interpreting sulphur recommendations, which are often given in pounds of sulphur (S) rather than sulphate. Sulphur can be applied using fertilisers or organic manure, with fertilisers often being readily available, while organic manure relies on mineralisation.
Synergy between Sulphur and Nitrogen
The latest innovation in nitrogen-sulphur fertiliser is Dynamon from OCI. This fertiliser has an ideal N/S ratio of 24% N and 7% S. A unique feature is the synergy between nitrogen and sulphur. When both elements are available in sufficient quantities, a plant can effectively absorb and utilise N and S. Importantly, both nitrogen and sulphur are required for protein synthesis. If one of the elements is missing, synthesis is affected, which can impact yield and quality. Dynamon is applicable and effective in all forage and arable crops.
Want to know more about OCI Dynamon? Read the information at www.oci-dynamon.co.uk.