When I came back to Finley after coordinating NSW DPI Research and Extension at Yanco Agricultural Institute for eight years and retiring, I restarted the discussion groups as a consultant in 2011 and reviewed the Ricecheck checks and agronomic data.
Chapter six, Production of Quality Rice, had a table of nutrient requirements for 12 tonne rice.
It was 10kg of sulphur per hectare for for 12 tonne per hectare rice.
The balance for sulphur was 13kgS/ha because most sulphur came from irrigation water at 18kgS/ha.
I requested Jeff Barrie, of Rees Fertilisers in Finley, to do water sampling in the Mulwala channel and obtain an analysis of the water samples.
Two samples carried out three months apart showed the sulphur was 6.4kgS/ha and 7.4kgS/ha.
This meant the sulphur balance, instead of being positive, was negative at -7 and -6KgS/ha.
This initiated a review of the critical soil test sulphur level of 5mg/kg.
It’s recommended for high yields to be at least 10mg/kg.
It led to a lot of farmers applying fertilisers with higher sulphur levels on a total farm basis.
I have had feedback that sulphur may be low again in some crops, restricting high rice yields with unexpected better yields from 1t/ha gypsum (17 per cent sulphur) or bore water.
Another factor is the low sulphur in MAP and DAP.
A standard sulphur fertiliser is Sulphate of Ammonia, with 100kg/ha supplying 24kgS/ha and 21kgP/ha.
I don’t know whether SuPerfect Super (similar to single super) is still sold, but 170kg/ha supplied 19kgS and 15kgP/ha.
If you think your paddock may have low sulphur levels, a demonstration of your standard sowing fertiliser package in one bay could be compared to a higher sulphur fertiliser package in a next door bay.
Sulphur deficiency rice can have reduced plant height and stunted growth, yellowing in younger leaves (nitrogen deficiency is in older leaves), less tillering, shorter panicles and reduced grains per panicle.
This article focuses on sulphur, but we also focussed on phosphorus application which led to a significant increase in rice yields.
~ John Lacy (pictured) is an independent agriculture consultant, based in Finley, and is founder of the Finley Discussion Group.
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