Issue 7 2019
Contributing to brassica nutrition in the country where cabbage is king

Raw, pickled, fermented, stewed, steamed, sautéed, braised and stuffed: the number of ways that people in Turkey like to eat their cabbage is certainly impressive! But the results of recent research in how best to nourish the cabbage crop all point to one best practice: use Polysulphate along with conventional SOP or MOP fertilizers for optimum yield.
Keeping up cabbage productivity

With such a traditionally popular crop, many traditional methods of crop nutrition evolve. Many farmers are content to continue with low input: low output cabbage-growing. But with production of 30 million tonnes of cabbage a year barely keeping up with national demand for this brassica in Turkey, some growers are wanting to maximize productivity by cost-effective and targeted cabbage crop nutrition along with other targeted inputs and techniques such as drip irrigation.

However, the usual application of conventional nitrogen and phosphorus fertilizer is unlikely to be completely beneficial without adequate S (increasingly important due to declining atmospheric sources) and additional potassium to guarantee the desired size and quality of cabbage heads.

Investigating fertilizer performance

Recent research in Turkey, supported by International Potash Institute (IPI), investigated the performance of different potassium fertilizer sources, all applied before planting at a dose of 300 kg K2O ha-1, including treatment with Polysulphate on its own and in combination with SOP (sulphate of potash).

Extracting information and lessons from multi-faceted research, especially with multi-nutrient fertilizer such as our Polysulphate, is a complex and careful process. However, there are some key findings.

Applying K, S, Ca and Mg – the nutrients in Polysulphate – significantly enhanced cabbage total and marketable yield. The combination of Polysulphate and SOP gave rise to the highest marketable yield, 81 Mg ha–1 (ton ha-1) with significant increase 59% more than the control.

Even better results were obtained when combining Polysulphate with SOP which resulted in the cabbage marketable head weight increasing to 4.22 kg from 2.68 kg (under the control treatment).

Polysulphate with SOP  not only gave significantly higher yields, but also better produce quality (increased phenolic compounds and antioxidant activity).

Enhanced Ca and Mg uptake, the main donor of which was Polysulphate, provides an explanation for the advantage of treatments with Polysulphate. Without Polysulphate​​​, the leaf contents of these two nutrients were at or below the minimum edge of the optimum range.
Effect of fertilizer treatments on the total and marketable cabbage yields. Identical letters indicate no significant difference (p<0.001) between treatments within each yield category.

The research concludes that this could be the most productive solution for Turkish cabbage farmers. This combination was also the best when it came to measurements of the full range of cabbage quality parameters within them. For more information, the full research report is available.
Matching advice on crop nutrition to farmer ambition

In our work with farmers, we always recognize the importance of demonstrating crop performance with Polysulphate and matching our advice to practical reality and grower aspirations for their farming systems.

With targeted, precise and balanced crop nutrition, cabbage productivity and profitability can be improved. That’s good news for farmers and for consumers. It means that Polysulphate can play its part in helping to keep all those delicious cabbage-based Turkish dishes coming to the table!
A view of the experimental field in Antalya region of Turkey. Photo by the authors.
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Mined in the UK, ICL is the first – and only - producer in the world to mine polyhalite, marketed as Polysulphate™