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What’s limiting your production?

What are the limiting factors to production when applying macro nutrients and lime? This is the question the TopSoils project is investigating through an omission trial in Gippsland supported by the East Gippsland Catchment Management Authority, through funding from the Australian Government’s National Landcare program and Southern Farming Systems.

In 2014 the TopSoils Project conducted 200 plus random soil samples across the region to determine baseline soil nutrient levels. These results indicated most soils were acidic, with nitrogen at either end of the scale of excessively high or extremely low; sulphur and potassium were commonly low enough to limit production throughout the region.

Hence, a 3-year omission trial was designed to focus on key soil constraints of Nitrogen(N), Phosphorus(P), Potassium(K), Sulphur(S) and acidity to study the impacts of applications of nutrients and lime on farmland that has had no previous fertilizer history. The trial in its’ second year was sown to a wheat crop on 31st May 2020 with randomized replicated trial treatments of N,P,K, S and Lime carried out throughout the season.

The 2020 harvest trial results showed the nil treatment averaged 3t/ha, by adding phosphorus, potassium and/or sulphur increased the average grain yield to 3.7t/ha and when you added Nitrogen to the P,K,S treatments it further increased the average yield to 4.2t/ha, providing a positive result to all treatments.

Where no lime was applied the average yield was 3.7t/ha and where Lime was applied it increased the average yield to 3.9t/ha. There was no interaction between lime and nutrient application, meaning that the effect of lime and nutrients were consistent and did not affect each other in terms of grain yield. It is to be noted that Lime takes a long time to move through the soil profile to address the acidification, therefore a long-term approach needs to be adhered too and increased productive results will occur overtime.

SFS Project Officer Natalie Jenkins said “The 2020 results were interesting and this year’s 2021 crop results will be much anticipated; giving us a good data set to investigate the economics and return on investment, which will provide a true indication of the impacts of nutrient & lime applications on the farm business”.

For more information on this project and updates contact Natalie Jenkins, SFS Project officer,  E:njenkins@sfs.org.au

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