Sustainability and Soil Health

Insight by Richard Salvage

Sustainability and Soil Health

Why is the health of soil depleting?

To compensate for nutrient availability problems and the loss of nitrogen, phosphorous and other nutrients from production systems, growers often need to apply more chemical fertiliser than their crops actually require. These excess nutrients accumulate in the soil and are then lost into the environment, polluting the air, rivers and lakes (Vance, 2001).

What is soil biodiversity?

The overuse of fertilisers, however, can significantly reduce soil biodiversity. Soil biodiversity encompasses the variety of life within soil, including microorganisms such as bacteria, fungi, protozoa, and macro-organisms like earthworms and insects. Fertilisers, while crucial for enhancing plant growth and agricultural productivity, can have several detrimental effects on soil biodiversity when used excessively. Geissler and Scow (2014) showed that long term application of nitrogen fertilisers led to decreased microbial biomass and altered microbial community composition, negatively affecting soil health.

The impact of nitrogen

High levels of nitrogen from fertilisers can create an imbalance in soil nutrient composition. This can inhibit the growth of certain microorganisms that thrive in low-nitrogen environments while promoting others, leading to reduced microbial diversity.
The overuse of nitrogen-based fertilisers often results in soil acidification. These lower pH levels can harm sensitive microbial species and alter the overall microbial community structure. Acidic soils can suppress beneficial bacteria such as nitrogen-fixing bacteria, which play a crucial role in nutrient cycling. Mäder et al. (2002) reported on long-term trials comparing organic and conventional farming systems. The results showed that organic systems, which rely less on synthetic fertilisers, had higher soil biodiversity and better soil structure.

Organic matter is a key habitat and food source for soil microorganisms. However, fertilisers can reduce the accumulation of organic matter in the soil, as plants rely more on synthetic nutrients. A reduction in organic matter can then lead to a decline in microbial populations and diversity.

Why is soil health so important?

Soil biodiversity is integral to many ecosystem functions like nutrient cycling, soil structure maintenance and plant health. Reducing this biodiversity can impair these functions, leading to poorer soil health and reduced agricultural productivity over time. Hartmann et al. (2015) emphasized that excessive fertiliser use, leads to a decline in microbial diversity and functional gene abundance, which are critical for soil ecosystem services.

Diverse microbial communities can enhance soil resilience to environmental stresses such as drought, disease, and climate change. A loss of biodiversity makes soil ecosystems more vulnerable to these stresses, potentially leading to crop failures and reduced agricultural sustainability. Therefore, it is a key objective of the agricultural and horticultural sectors to find ways to reduce excessive fertiliser use while being able to accommodate increasing global food demands.

How can complex biostimulants help?

Using complex biostimulants, farmers and growers can reduce the amount of fertiliser they use. They can also develop crops that have great resistance to the external stressors that usually impact growth and development. The synergistic effect of complex biostimulant products, like Maxstim, is optimising plant growth and showing nutrient use efficiency.

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