Chief Executive, Rothamsted Research

What is site specific nutrient management and why does it matter? 


In the past 60 + years we have experienced a fairly linear correlation between global fertilizer use and global crop production. This has been one of the key trends associated with the Green Revolution, and often it was driven by quite general fertilizer recommendations. Nutrient use as well as nutrient use efficiency vary greatly worldwide, including significant losses into the environment or even soil nutrient mining in some regions.


I define site-specific nutrient management (SSNM) as the dynamic, field-specific management of nutrients in a particular cropping season to optimize the supply and demand of nutrients according to their differences in cycling through soil-plant systems. This form of SSNM attempts to account for (i) regional and seasonal differences in the climatic yield potential and crop nutrient demand, (ii) between-field spatial variability in indigenous nutrient supply, (iii) field-specific within-season dynamics of crop N demand, and (iv) location-specific cropping systems and crop management practices.


It matters greatly because it aims to tailor fertilizers and other nutrient inputs to the specific crop needs and thus increases yields, profit and nutrient use efficiency, while minimizing nutrient losses and soil depletion. It can be done with sophisticated technology in large fields, or with simple decision aids in smallholder farming.


What are the new and promising ways that SSNM can be further improved?


In the past 20 years many on-farm studies have demonstrated that with SSNM yields and profits typically increase by 10-20% (or more) and nitrogen use efficiency often increases by 30-50%. Nevertheless, many improvements can be made. Key areas include: (i) further improvement of the underlying scientific basis and algorithms, (ii) inclusion of a wider range of secondary and micro-nutrients, (iii) making use of novel field diagnostic tools for soil and plant analysis, (iv) incorporating real-time remote sensing and weather data at high spatial resolution, (v) site-specific fertilizer design, and (vi) machine learning/artificial intelligence for improving predictions and making it easier to use in practice.


How can we optimize knowledge transfer to farmers?


In my view, effective knowledge transfer requires humans as well as technology. Data-driven approaches and new ICT tools now allow us to do this much better than ever before, with a lot of the knowledge available at our fingertips, in the field. However, we need to rigorously capture, process, evaluate and re-package knowledge so that it is evidence-based and FAIR (Findable, Accessible, Interoperable and Reusable). Many things are still too complicated for practical use and people need to be grounded in the field with everything they do in knowledge exchange, which I think is the better term to use because scientists also must learn a lot from extension workers and farmers. In many countries we will need “armies” of agronomists who can make use of new knowledge and tools but are trusted experts in the field.


How can a multi stakeholder forum such as this one help to identify further research priorities into plant nutrition?


The past few decades have shown that nobody can do it all alone. We generally have an underinvestment by both public and private sectors in soil science, plant nutrition and fertilizer research. We haven’t had major breakthroughs in these science areas in recent years, probably for that reason, and there is also a never-ending debate about the role of nutrients for global food security vs. nutrient pollution and regulation. Hence, I believe that we can only achieve more transformative changes if different stakeholders work more closely together, agreeing on the priorities and co-investing in them over the longer term. We need new public-private partnership models for that, and I hope this forum can take us one step closer to that.