Sulphur: the unsung hero

Better soils
with Brett Petersen
Kiwi Fertiliser & Golden Bay Dolomite

 Kiwi Fertiliser has many clients throughout the North Island, and it greatly pleases us that when we increase sulphur from sub optimum to optimum levels, both plant and animal production increases including more and better pasture, milk in the vat, higher lambing percentages and greater carcass weights.

Why are most of our soils so sulphur deficient? Lack of awareness of true soil fertility can be harmful and can create a multitude of problems from soil nutrient excesses to plant deficiencies and animal health issues. This is a cost to the grower or farmer by limiting economic prosperity. 

Of course Sulphur cannot act alone and must be in balance with all other nutrients. We invariably add sulphur to Sechura RPR, or other phosphate sources. This leads to natural acidulation in the soil and enhances the Sechura RPR effects. Where phosphate is not applied, sulphur is still required.

Rarely is sulphur found in excess; more often it is deficient. This usually occurs because insufficient is applied. It is also dependent upon organic matter in the soil. We often hear you cannot build sulphur levels, but we find the opposite is true. Sulphur is an anion and attaches to the positively charged organic matter. This is true of other anions.

Organic matter is important to be able to build anion levels in the soil. (ppm – parts per million – relates to graph below.)


OM %





























Sulphur is indispensable for many reactions in living cells. It plays vital roles in plant and animal nutrition. It is a constituent of amino acids, vitamins, protein, enzymes (90 per cent of total S in plants). Legumes (for nodulation), brassicas, onions, garlic and similar plants have a high sulphur requirement.

Often, sulphur deficiency is masked by superphosphate applications, with the response seen owing to sulphur, not phosphate.

We need to see over 25 ppm of SO4 of plant available S; on dairy and intensive units 50ppm. There are many farmers/growers that already understand the importance of sulphur, so they add good quality elemental sulphur. They know the benefits of correct soil sulphur levels.

Sulphur can strip out cations from soil. Some soil chemists in NZ say there is no economic benefit in liming soils. They do not understand commercial fertiliser applications. We are often disappointed when a farmer or grower may say they have an optimal pH of 6.3 only to find the pH is “correct” but the cations are not. The more anions introduced to soils the more cations will be displaced. This needs to be properly managed and corrected. An example of this is the “blind” application of Gypsum. In some circumstances, the sulphate will actually reduce total calcium in the soil. That’s fine if it is the intention, but counterproductive if calcium needs to be increased.

So how do we build sulphur levels and minimise sulphur leaching? We at Kiwi Fertiliser have many farmers and growers doing exactly that. The top 5 per cent of farmers and growers use long-term thinking to plan for the future. Correct soil fertility is part of that strategy.

A soil fertility plan will improve the soil, plants, animals, and profit for 10 or 20 years and more. Please get in touch with us for a discussion, soil tests and follow up recommendations.


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