Output 1.

By April 2029, tools that predict plant responsiveness to applied potassium fertiliser developed across diverse soil types in the Southern and Northern GRDC regions.

Growers will have confidence that soil and plant tissue testing guidelines will identify whether K deficiency is a risk in their soil. To ensure soil tests are useful, new guidelines should be representative of K availability to the crop. This could involve recalibration of existing tests to a greater soil depth, new critical values, or incorporation of other soil measures to adjust for soil texture and/or mineralogy. Guidelines will include soils across texture gradients and varying mineralogy. Testing should include recommendations for different crop types and validate plant tissue critical levels. Agronomists and plant and soil testing companies are to be consulted and included in a consultative committee at the start and throughout the project to ensure potential barriers to adoption of tools developed through this project are considered and addressed. This includes ease of sampling by growers and advisors and incorporation of testing guidelines within companies’ protocols.

Technical findings on new critical values and improved ability to predict plant response will be provided in relevant formats to provide scientific credibility to findings and underpin guidelines if new methods are required (e.g. peer reviewed scientific publications, conference proceedings etc.).

Information from this output must be presented in a format suitable for growers and advisors and will inform Output 3, to identify when and where they have soils that are at risk of K deficiency and a response to applied K is likely.

Output 2.

By April 2029, quantify crop recovery of K fertiliser across multiple seasons for key crops in the Southern and Northern regions.

Quantify crop recovery of K fertiliser in soils of the Southern and Northern region across multiple years (i.e. year of application and residual value) and determine the influence of soil texture and mineralogy on K dynamics in soils.

Project team will engage with SWAN Strategic partnership team to facilitate cross-project collaboration, sharing of learnings and consistency of methods (where appropriate). Data may be derived from laboratory, controlled environment and field-based studies across the regions of interest and may use isotopic tracer techniques to quantify uptake.

Experiments should investigate how the rate, placement, timing and source of K fertiliser influence crop recovery across diverse soil types and their interaction with the environment (climate and farming system) noting differences between seasons and the role of subsoil vs topsoil moisture, nutrient stratification and nutrient availability.

This information must be presented in a format suitable for growers and advisors and will inform Output 3, where recommendations for fertiliser management to maximise fertiliser K use efficiency and return on investment will be delivered.

Output 3.

By April 2029, potassium management recommendations that maximise KUE and return on investment for soils across all GRDC regions.

Develop and deliver recommendations for growers and advisors that maximise return on investment of applied K fertiliser. Recommendations must incorporate learnings from past GRDC investments, and the current investment (Outputs 1 and 2) and provide evidence of the current risk of K deficiency and K stratification across soil types. Recommendations will include considerations of the tools available to growers to identify K deficiency including soil testing, plant testing, test strips and nutrient budgeting. Project team will work with SWAN Strategic Partnership team to incorporate recommendations and research from the Western region and on lighter soil textures.

Recommendations will consider crop requirements, soil concentration, availability and dynamics within the profile, and the interactions with soil type (texture and mineralogy) and environment for current Australian farming systems. Scenarios and high fertility farming systems where K supply and dynamics in the soil is sufficient to reduce or not apply K fertiliser will be included.

Output 4.

By April 2026, and annually thereafter delivery of extension knowledge emerging from outputs 1 to 3 inclusive.

Prior to completing a communication, extension and adoption plan undertake a SWOT analysis of past RD&E (including but not limited to past GRDC investments UQ00063, UQ00078, UQ00082, UMU1801-006RTX and DAW1801-001RTX). Review existing GRDC communication products and resources (fact sheets, manuals etc) on soil testing guidelines and potassium management. Existing and new K knowledge (Outputs 1-3) compiled and disseminated annually to growers and advisors through multiple pathways including GRDC channels (Groundcover, GRDC Updates, webinars, NGN events etc) and other opportunities.