Polysulphate Raises Organic Raisin Yields

David Holzhuizen farms in Upington in the Northern Cape province in South Africa, where the grapes from his vineyards are used for organic raisin production. When he started his organic raisin production, he encountered many initial problems but worked through them to find the solutions that worked best for his crop, farm, and bank account.

Visit the vineyards now and you will see healthy, productive vines producing good yields of high-quality grapes destined for the organic raisin market. But this was not always the case.

Organic Production Challenges

When David Holzhuizen started growing organic grapes for raisin production he faced some difficult years.

“It was a difficult road to travel when I got here and started growing organic grapes”

Transitioning from chemical fertilizers led to challenges such as late and uneven blooming, and even crop failures at times, as David tried various crop nutrition options for his organic grapes.

Polysulphate Produced Excellent Results

About 4 years ago, he started using ICL’s Polysulphate fertilizer on his vineyard. As David explained to Derek Rosmarin, the ICL Growing Solutions agent in South Africa, the switch to Polysulphate produced excellent results, with some of his best vineyards yielding up to 8 tons per hectare of organic raisins, and an average of around 6 tons.

For David, it is not just the crop yield that is excellent. Soil tests revealed there is a lot of soil life, with a wide variety of microbes in the soil, and leaf analysis of the vines shows excellent crop health too.

“It’s really a blessing to have Polysulphate available”

As far as the costs are concerned, David describes Polysulphate as a blessing, saying it is not as expensive as the herbicides and insecticides he would have applied to his conventional grapes, helping to keep the overall input costs down.

Sustaining Vine Health

Applying 100-150 kg of Polysulphate underneath the vines with a spreader every 50 days supports the vines right through the growing season, and the dormant period too. This is where David says the vineyard speaks for itself, providing an excellent yield, and then after harvest, there is a lot of re-growth, helping the vines recover after harvest and build reserves for the next growing season.