RiskWi$e – Nitrogen Management Decisions

Outcome

It is anticipated that within five years, 80% of growers can articulate their production management decisions couched in terms of probability of upside returns offset against the associated downside risks.

Growers are nationally engaged and challenged in participatory action research to provide them and their advisers with improved understanding and actionable practices regarding the reward and risk outcomes for key management decisions on their farms.

Outputs

There are 5 themes in RISKWI$E

• Nitrogen (N) decisions: The nitrogen (N) decisions theme will take a whole-of-system approach to help growers assess N decision strategies encompassing fertiliser and legume use.
• Sowing decisions:The sowing decisions theme will develop long-term strategies to help determine sowing location, varietal selection and sowing timing while considering landscape, farm and paddock conditions.
• Enterprise agronomic decisions:The enterprise agronomic decisions theme will investigate crop sequence decisions from crop choice, fallow choice, soil amelioration and weed/disease management strategies.
• Enterprise financial decisions: The enterprise financial decisions theme will help with decision making related to farm economies of scale, operating costs, commodity prices and marketing, grain storage availability and labour management.
• Managing natural resource capital:The managing natural resource capital theme will help growers make decisions that support improved soil health and soil carbon, reduce greenhouse gas emissions and non-chemical weed.

WANTFA/MADFIG Nitrogen Decision theme

Australia’s annual consumption of N fertiliser (1.5 Mt) is about 1% of the world’s consumption and the total N in the top 10 cm of soil has been decreasing in dryland cropping systems in Australia (Angus and Grace, 2017). Nitrogen (N) deficiency is one of the main causes of the exploitable yield gap for wheat and canola production in Australia. Under-fertilisation can also result in low protein grain that attracts a lower price.

Currently, growers aim to provide N when the plant needs it the most but by the end of the season, all the soil N is exhausted. In comparison to the “on-the-go” N application routine, applying high N rates and “topping up” the soil N bank increases both crop yield and also soil organic carbon (SOC) by allowing more C fixation in plant biomass and the soil (via plant roots and residues) (Smith et al., 2019; Meier et al., 2021).. Paddock variability is also a big factor and decisions around variable rate across a padock can save substantial fertliser inputs.

High N input carries many risks, especially financially. Whilst N loss is relatively low in stubble retained paddocks in mid to low rainfall areas, long-term high N input can lead to increased nutrient leaching and decreasing soil pH.  The reward will be accessing the carry over of N (the N bank) in following years so that the initial investment is not wasted.  The ability to VRT the paddock with N will also decrease costs and optimise profit across the paddock while evening out grain protein levels.