Issue 8 2018
Lots from pots: Latest evidence from trial on alfalfa points out Polysulphate potential
To get to grips with how to improve the big picture, sometimes it is better to look at the small detail for answers. That’s why we are very interested in the results to come out of an experiment looking at how best to improve potassium levels for the Brazilian alfalfa crop by using Polysulphate rather than alternative fertilizers such as gypsum or potassium chloride.

Potted studies offer powerful insights

The work at the regional research center of the national agricultural science network EMBRAPA began with pots and pots of alfalfa, and a plan of lots of different treatments to replicate both conventional and also potentially better practice. Using containers allows researchers to replicate treatments without the variables that in-field trials can throw into the mix.

Finding fortitude in fertilizer use

Fertilizer use in Brazil has risen fast. The nation now ranks fourth in fertilizer usage worldwide. A lot of it is potassium fertilizer as Brazilian soils tend to be deficient in this essential plant nutrient. However, farmers are concerned that they are not giving adequate, prolonged effective nutrition to their crop. This is why the results of using Polysulphate is of interest because not only does it deliver potassium, but it also offers sulphur, magnesium and calcium as well.

Capturing results that resonate with farmers

Measurements of the alfalfa growth in the pots were recorded after the different treatments. The results of seven successive harvests demonstrated firstly that supplementing potassium was essential for good yield. They also revealed that Polysulphate application, alone or in combination with potassium chloride, gave rise to significantly higher biomass yields of alfalfa than potassium chloride, with or without gypsum. Moreover, Polysulphate significantly enhanced potassium, sulphur, calcium and magnesium uptake, particularly when applied alone at the highest dose.
Alfalfa dry biomass production in response to K application (rates of 50, 100, and 200 kg K2O/ha) in a pot-grown experiment.
From lots of pots to lots more plants

The next stage is of course to scale up the research to see if the same results occur on field-scale alfalfa. But this pot work is a very important first step in the journey to influencing big changes in Brazilian fertilizer use for better alfalfa harvests.

More information is available in the full research paper available from the International Potash Institute.
Alfalfa plant performance without K application and using Polysulphate or KCl+gypsum at 100 kg K2O/ha. Photo by A.C.C. Bernardi.
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Mined in the UK, ICL is the first – and only - producer in the world to mine polyhalite, marketed as Polysulphate