Spring pasture growth is often impacted by a shortage of plant-available sulphate sulphur.

“Without adequate levels of sulphate sulphur, spring pasture’s nitrogen response efficiency may be limited,” says Ballance Agri-Nutrients Science Extension Manager Ian Tarbotton.

Wet, winter conditions are the main culprit. “Over winter, rainfall increases the leaching of sulphate sulphur. Plus cold temperatures slow down the bacterial conversion of non-plant available elemental sulphur provided by fertiliser and organic sulphur found in the soil into sulphate sulphur,” Ian explains.

Pastures deficient in sulphur (S) appear pale green or yellow, with clovers affected first. Clover in particular needs S to efficiently fix nitrogen (N) and less clover in a sward means the supply of N to other pasture species is reduced.

Spring herbage testing can complement soil testing when deciding if S is required for a good pasture response to N application as shown in Table 1.

Sulphur can be applied with other nutrients in spring or autumn, depending on the leaching risk as shown in Table 2.

In spring, SustaiN Ammo products provide the ratio of N and S pasture requires and the S content is sulphate S, readily available for plant uptake. SustaiN reduces the amount of N lost as ammonia gas and increases N efficiency. It provides greater flexibility in application timing as SustaiN does not need at least 10 mm of rain or irrigation within eight hours of application to reduce N losses as ammonia gas.

For autumn S applications, a fertiliser containing elemental S should be used. PhaSedN contains elemental S and N (SustaiN) to support rapid pasture growth and a small amount of lime. The fine elemental S remains in the soil over winter and starts releasing in early spring, while SustaiN provides N for an immediate autumn boost.

The fine elemental S particles are designed to supply sulphate S rapidly. University of Waikato studies have shown that, on average, 60 percent of the elemental S particles in PhaSedN are under 0.075 mm in diameter, compared to around 20 percent of particles in this range for other elemental S products in New Zealand.¹

Speak to your local PGG Wrightson Technical Field Representative to organise spring herbage and soil testing.

1 Report prepared for Ballance Agri Nutrients. (2015). PhasedN vs Sulphur Gain Pure & Sulphur 90. A comparison of elemental sulphur particle fineness and testing methods.

Table 1: Sulphur (S) content of spring mixed pasture samples and impact on nitrogen (N) response

Table 2: Leaching risk and sulphur (S) application