What soil information do crop advisors use to develop nitrogen fertilizer recommendations for grain growers in New South Wales, Australia?

Abstract

The Australian grains industry relies on mineralized nitrogen (N) from soil organic matter and plant residues, but fertilizer N is increasingly needed to optimize yields. Most farmers are guided on N fertilizer requirements by commercial crop advisors. We surveyed (n = 132) and interviewed (n = 11) New South Wales grains advisors to gauge the usage of soil process understanding, soil data and decision support systems (DSSs) when developing N recommendations. Soil moisture at sowing, seasonal forecasts, crop rotation, soil mineral N, financial risk profiles and paddock history were all used to prepare N fertilizer advice, but stored soil moisture was most important. Farmer confidence in soil N testing was low due to high spatial variability. Most advisors calculated N fertilizer required for yields within 10%–15% of crop potential, but clients’ attitude to financial risk guided final N recommendations. Conservative growers preferred a low input system, while more reliable rainfall or greater reliance on stored soil water led growers to apply higher N rates to maximize long‐term profits. Advisors preferred “rules‐of‐thumb,” simple DSSs and knowledge of crop growth, to elaborate DSSs requiring detailed inputs and soil characterization. Few used in‐crop N sensing. N decision methodologies need to be updated to account for changes in soil fertility, cropping systems and farming practices. New research is needed to answer practical questions regarding soil N mineralization and N losses associated with alternative N application practices and extreme weather events. Training of new advisors in N processes and DSS use needs to be ongoing.

Sustainable soil use and management: An interdisciplinary and systematic approach

“…In Australia, the New South Wales local government uses webinars to disseminate soil science information to a geographically disperse community of practice (CoP) (Jenkins et al, 2019). Grain advisors, however, were reported to be guiding farmers to historically established "rules of thumb" for calculating nitrogen fertilizer needs, rather than the latest evidence-based science on soil water and nitrogen management (Schwenke et al, 2019). Another Australian local government decided to share soil information and knowledge using a website coupled with training workshops.…”

“…In Australia, farmers apply the recommendations of professional crop advisors to select suitable fertilizer dosages. However, attitudes concerning financial risk, soil heterogeneity, and local climate conditions can affect their perception and adoption of such advice (Schwenke et al, 2019). In Europe, a knowledge gap regarding sustainable soil management was identified as a major issue among both farmers and soil advisors.…”

Assessment of the Use of Geographically Weighted Regression for Analysis of Large On-Farm Experiments and Implications for Practical Application

“…Experiments might compare discrete treatments such as the variety [19] or types of soil amelioration, quantify response to different rates of a single treatment such as fertiliser or fungicide [16,20,21], or consider multiple treatments. Various designs are used, including strip trials [22][23][24][25][26][27], nitrogen-rich strips [28], and checkerboards [29,30].…”

Knowledge sharing and adoption behaviour: An imperative to promote sustainable soil use and management

“…One interesting dynamic introduced by soil advisors is that they tend to digest information from scientific studies and modelling exercises, with local parameters incorporated, and then come up with 'rules-of-thumb' which give estimates that are 'roughly right'. They would then omit more robust soil data and decision support systems (Schwenke, Beange, Cameron, Bell, & Harden, 2019 2 | KNOWLEDGE SHARING:…”