Potassium responses in winter crops and pastures

In collaboration with NSW DPI and the GRDC, the response of wheat and barley (Warndoo 2015) and wheat, triticale and canola (Breadalbane 2015) are being investigated. Responses of wheat and canola to K are assessed at Glenthompson (2016) with Southern Farming Systems and the reponse of pasture yield and quality to N, K and Mg is being addressed at Bessiebelle. Additional demonstrations have been undertaken on pastures in coilaboration with Meridian Ag P/L. Support of these trials is provided by Canpotex P/L and IPNI ANZ.


02 Jun 2018

2017 Annual Interpretive Summary

A field site was selected at Glenthompson in the high rainfall zone of southwest Victoria, Australia to further evaluate the responses in that region to potassium (K). The site selected was of moderate soil K status (assessed by bicarbonate extraction at 50 mg/kg K), although the reported critical values for soil test K are uncertain for these soils and environments. Five rates of K (0, 25, 50, 100, 150) were applied at seeding to wheat, canola, and faba beans in a small plot experiment.

Growth and yield of these crops were assessed and there was a significant interaction between the crop and K application. Canola yields increased from 2.4 to 3.1 t/ha with 25 kg K/ha, and to 3.4 t/ha with 50 kg K/ha. There was limited increase beyond this rate. Over the 0 to 150 kg K/ha rates, wheat yields decreased by 8% (4.4 to 4.0 t/ha). There was no significant response to K on faba beans although there was highly variability, probably due to poor nodulation in the pulse, a consequence of a relatively low soil pH and high exchangeable aluminium levels on the site (ex-Al 9% of CEC). There were also no differences in the found in the timing of the applications for the 50 kg K/ha treatments. The mid-season differences can be viewed on-line at http://anz.ipni.net/article/ANZ-3302. Soil test information, mid-flowering biomass results and yield graphs can also be found on that site.

The results from this project will be added to the Better Fertilizer Decisions for Crops database to help improve regional soil test guidelines.