In this blog post, we’re discussing the relationship between microbial populations in soil and the effect of commercial cropping and fertilisation.
Microbes are no wallflowers!
We generally associate agricultural fertiliser applications with improved plant growth. However, it’s important to remember that fertiliser nutrients are not only exposed and available to the plant, but also to all the organisms and microbes within the soil system.
We know that soil microbes play an important part in getting nutrients into plants, so these become a crucial factor in overall plant health. That’s why we need to consider the impact of intensive fertilisation on the numbers and activities of native microbes in the soil.
Swipe left or swipe right?
The most commonly held perspective is that fertiliser applications have a negative effect on soil microbes. Fertilisers, especially inorganic fertilisers, are often associated with upsetting the microbial balance and therefore the health of the soil. While this may be the case in some instances (particularly with regards to the excessive applications of products such as potassium chloride and nitrates), fertilisers are still an essential component of viable cropping, including those microbes that play an important role in facilitating the uptake of most nutrients required by plants.
Recent advances in technology have allowed researchers to better measure the total microbial biomass and identify the specific microbial families in the soil in order to assess the impact of fertilisation on the soil microbes.
The observations are complex, for example:
- The application of nitrogen may decrease the number of nitrogen-fixing bacteria in a sample. However, the same application could increase the total amount of microbes involved in degrading crop residues.
- Fertiliser applications increase enzyme activities related to nutrient cycling.
- Some findings show that fertilisers promote microbial growth and activity, which goes against commonly-held beliefs.
Fertiliser: friend or foe?
Like all relationships, there’s no ‘one-size-fits-all’ approach as there are so many variables involved. All soils, microbes and fertilisers are unique, and different environments have varying interactions between these elements. Some of the factors influencing the relationship include:
- soil type
- native microbe populations
- fertiliser amounts, placement and formulations.
Interactions among soils, microbes, fertilisers and plant roots occur in various combinations. So, just like human compatibility, what works for one environment doesn’t necessarily work for the next! In particular, the microbial population in the soil, especially in the root hair soil interface (rhizosphere), is extremely complex.
Thus, applying the correct fertilisation is not just a matter of inputting a fertiliser that worked for a fellow farmer and waiting for an amazing yield.
The ‘make or break’ moment
Photosynthesis is the critical process that determines plant quality and yield. If the delicate rhizosphere balance is not optimal, photosynthesis will be compromised. The first signs of compromised photosynthesis are disease and insect pressure.
As the single most important natural process on Earth, photosynthesis is dependent on naturally-available elements – carbon dioxide, water and sun (all free!) – for 95% of its function. The balance (5%) comprises nutrients taken up by the plant. In nature, these nutrients are also free; in commercial agriculture, they are added in the form of organic and inorganic nutrients.
Thus, there is a role for fertilisers to play in commercial farming practices. However, the application of fertiliser requires a tailored approach of what should be applied, and when it should be applied – all dependent on the condition and nature of the soil.
Here’s what we do know:
A healthy soil requires much more than the handful of nutrients that usually make up inorganic fertilisers. The diversity of the soil microbe can be improved by:
- cover crops
- green manures
- products derived from organic raw material, such as fish hydrolysate (natural amino acids), Amino K (fermented molasses) and kelp (plant hormones).
These organic products are efficiently taken up directly by plants as foliar applications, but are most beneficial as microbe food sources in the soil. The rich concentrations of amino acids, fermentation metabolites, plant hormones, soluble carbon (as opposed to humus), to name a few, act as immediately-available microbial food sources. This stimulation of the soil microbial population triggers and magnifies the uptake of more traditional nutrients (macro, micro and trace elements), and thus results in a better yield.
A relationship built over time
Organic fertilisers can have a positive effect on the health, number and diversity of soil microbes. We’ve found that it’s best to apply small amounts of organic additives at regular intervals to avoid spikes in microbial activity.
Read more about Fertilisation: Quantity vs Quality
Zylem supports healthy soils and tailored fertilisation
At Zylem, we know that every situation is unique, which is why we offer our products on a consultative basis and include sustainable solutions that promote soil health.
Our Sea Brix is a biological product that contains fish hydrolysate, Amino K, kelp and Triacontanol. It was designed to primarily act as a soil-applied plant/soil/microbe food that ultimately enhances the uptake of existing soil nutrition along with added inorganic fertilisers. As with most natural and sustainable systems, balance is everything.
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Justin Platt – 083 264 6816 – email@example.com
Gill Platt – 082 577 4040 – firstname.lastname@example.org
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Our Technical Junior Manager, Nosipho Mbele, is on maternity leave; for any technical queries please contact Justin Platt.
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