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.


22 May 2017

2016 Annual Interpretive Summary

Earlier projects have identified that potassium (K) removal is increasing in high rainfall cropping zones (annual rainfall>550 mm) as the area and yield of crops both increase with crop intensification. Previous research in this region has shown responses to applied K. To provide additional information, two field experiments were undertaken during 2016. One focused on K responses for crops (wheat and canola) and the other on the effect of pasture quality on applied K, nitrogen (N) and magnesium (Mg).

The crop experiment investigated four rates of K (0, 25, 50, and 100 kg K/ha) applied as potassium chloride (KCl), either at seeding or topdressed at the five-leaf crop stage. The same trial design was used for wheat and canola, and the experiments were undertaken adjacent to each other. Soil K levels were moderate (90 mg/kg Colwell K) for pastures, but these critical values were high when interpreted for crops. The results showed no significant difference in emergence, growth or yield when K was applied either at seeding or later in growth. The seeder did have split seed and fertilizer delivery chutes, so the potential for in-furrow damage was low. During the growing season, symptoms of K deficiency were evident on the wheat crop, and canola showed extended maturity with applied K. There was a significant increase in wheat yield to 25 kg K/ha from 3.0 to 3.9 t/ha, but canola did not show any yield response.

The pasture experiment compared four rates of K (0, 25, 50, and 100 kg K/ha) applied as KCl, and two rates of N (0, 50 kg N/ha, as urea) combined factorially. The higher N rate was also split for two rates of Mg (0, 10 kg Mg/ha). The pasture yields were assessed by dry matter cuts in the late spring. There was a 10% increase in yield with the 25 kg K/ha rate when N was supplied, but not for when there was no N supplied. The response to K was higher where N was supplied, but there was little response beyond that rate. There was also a 10% increase in yield with Mg when averaged over the three applied K rates at the higher N rate. Fodder quality and nutrient content assessments are currently being undertaken.

Further research will be conducted in this region during 2017 to investigate the effect of timing and application rate for K applied to wheat, canola and fababeans.