Modern crops are often excessively fertilized, which boost yields in the short term but also harms the environment due to nutrient runoffs and greenhouse gas emissions.

Additionally, fertilizers are often inefficient because much of the applied fertilizers become bound to soil particles over the long term, making them unavailable for plants.

The application of high doses of easily soluble fertilizers may ensure crop productivity, but it comes at the cost of environmental quality and agroecosystem resilience. This fertilization strategy often results in “lazy” crops with underdeveloped root systems and reduced ability to acquire nutrients from native soil reserves.

As a pedologist (someone who studies soil formation) and biogeochemist, my research focuses on the multiscalar and interdisciplinary study of soil systems.

Improving resiliency

In Canada’s vast forests, the trees thrive in nutrient-impoverished soils because of the capacity of their deep root systems to acquire nutrients and water. In natural ecosystems, plants have evolved and developed root strategies that help to absorb nutrients.

One way they do this is by growing bigger, stronger and more active roots, which help them access more nutrients from the soil. Sometimes, they team up with soil micro-organisms to increase their capacity to access nutrients. As roots absorb nutrients, they also release certain molecules in the soil called root exudates.

These compounds contribute to breaking down organic matter and dissolving soil particles, making trapped nutrients accessible for plant root uptake. Root exudates are also a source of energy for soil microorganisms, which down the road also support soil carbon storage and enhance general soil health.

The SoilRes3 Lab at the University of British Columbia carries out interdisciplinary research on soil genesis to uncover how microscale processes shape macroscale ecosystem properties and resilience. Grounded in soil–plant feedbacks, our pedological work examines the complex relationships between land and people across diverse eco-cultural contexts, with the goal of strengthening ecosystem resilience, resistance and restoration.

Examining soil-plant feedback in natural ecosystems, we found that using a bit less fertilizer could actually benefit crops in the long run. By decreasing fertilizer, we could increase the production of root exudates. This enhances the plants’ ability to absorb nutrients on their own, rather than depending on external inputs.

By increasing microbial activity in the rhizosphere (the area surrounding plant roots) and acting as a direct carbon source into the soil, increased root exudates could also contribute to healthier soils.

plant roots in a forest
The rhizosphere is the area surrounding plant roots where the roots, soil organisms, nutrients and water interact. (Jordan Fernandes/Unsplash), CC BY

Alternative strategies

Nitrogen and phosphorus are the two most important nutrients for plant growth, and they are the most used fertilizers around the world.

Our team of soil scientists reviewed 36 studies encompassing 30 different crops and soil contexts. We compared how plants responded under two fertilization conditions: one with the usual amount of fertilizer to maximize yield, and another with less fertilizer, especially less nitrogen and phosphorus.

We found that cutting phosphorus fertilizer by up to half boosted root exudation by 30 per cent, while only slightly reducing crop growth by just two per cent. In contrast, reducing nitrogen fertilizer raises root exudation by seven per cent, but lowers plant growth by 20 per cent.

Our findings show that optimizing phosphorus use in agriculture can stimulate more active root systems and increase exudate production.

Soil types

Optimizing phosphorus fertilizer to boost root exudation without sacrificing yield depends heavily on soil type. Soils in British Columbia differ significantly from those in Manitoba, Québec and Saskatchewan, and the impact of root exudates on nutrient uptake and carbon capture varies with soil conditions (soil pH, mineralogy, moisture, texture).

That’s why our proposed strategy — limiting fertilizers to maximize root activity — must be tested in real-world settings, with farmers, across diverse soils and crop systems.

The next step will be to examine root exudation responses and effects under varying soil physicochemical and eco-cultural contexts. Field trials are essential to tailor this approach to local conditions and ensure its effectiveness and scalability.

This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: JT Cornelis, University of British Columbia

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JT Cornelis works for the Faculty of Land and Food Systems at the University of British Columbia, as an Associate Professor in soil science. He receives funding from NSERC Discovery Grant, NSERC Alliance, Killam Trusts and BC Genome.