AN update on an Australian-first trial to analyse the potential of Western Australian-produced sulphate of potash (SoP) fertiliser was provided at The University of Western Australia's (UWA) Institute of Agriculture glasshouse recently.
Members of the Hartley Investment Group and Australian Potash Company were in attendance at the update, which was provided by UWA Hackett professor of agriculture chair and director Kadambot Siddique and lead researcher Dr Zakaria Solaiman.
The Sulphate of Potash for WA Farmers project is a collaboration between the WA No-Tillage Farmers Association (WANTFA), UWA and the Australian Potash Company (APC), which is supplying the SoP from its Lake Wells site.
In May, WANTFA applied SoP to five paddock trial sites throughout WA and each site received between four to six treatments of SoP and MoP, with differences to crops and soil to be recorded through the growing season.
At the same time UWA is running a two-year glasshouse study to add scientific rigour by studying the yield and quality of crops grown in a controlled environment, in the same soils collected from the trial paddocks.
The four current glasshouse study experiments include:
Responses of wheat and canola to rates of sulphate of potash
Comparison of APC locally produced premium SoP and MoP on yield and quality of wheat and canola
Comparisons of potassium leaching of SoP and MoP
Germination and establishment of crops with SoP and MoP.
Professor Siddique said SoP had two major components - potassium and sulphur.
"WA farmers have traditionally been applying MoP, which has potassium and chloride," professor Siddique said.
"Potassium is an essential element and traditionally WA farmers haven't been applying a lot of potassium, but in the past 20 years continuous cropping programs have depleted a lot of potassium from our agriculture soils.
"The State wheat average yield has increased to two tonnes a hectare and so we are removing more grains per unit area and in some areas many farmers are harvesting up to four tonnes of grain plus the straw.
"Hay production also removes huge amounts of nutrients out of soils and so the soils have to be replenished.
"A lot of farmers have now been applying potassium fertiliser to their soils based on soil and plant tissue tests.
"The question we are asking in this trial is does SoP have any specific benefit compared to MoP, the normal fertiliser used.
"In order to test this we want to test egg versus egg, not egg v apple or apple v pear.
"So we have some experimental protocols where we apply gypsum, which has sulphur, to the MoP to balance things out.
"The trial will include four applications - MoP with gypsum, MoP application and SoP application and a control plot with nothing added."
Nitrogen and phosphorous was applied at the same level in all plots of the trial, except the control.
Two months into the trial, Dr Solaiman said there were noticeable differences coming through.
"There is a greater number of tillers where we have added the sulphur and there is a definite potassium deficiency in the plants that have had nothing added," he said.
"These plants are developing faster and coming into the booting stage a lot earlier, which is a sign the plant is under stress and this will impact yield.
"The next step is to take dry matter tests, tiller numbers, nutrient status and yield component tests.
"Plants will be taken all the way to maturity and be harvested around flowering time to see the biomass produced.
"At this stage the rates of SoP application is showing a significant visual increase in growth against the nil application."
Professor Siddique said a major difference between equivalent amounts of potassium plus sulphur was not expected in terms of growth.
"The difference may come in terms of grain quality and things like that, so we will need to look at protein of wheat grains and oil content in the canola," he said.
"Early growth is important but this experiment is designed for yield."
