AsianScientist (Mar. 16, 2015) – Adding too much fertilizer to the soil could backfire by increasing the growth of pathogenic fungi, according to a study published in Scientific Reports.
With global consumptions of nitrogen fertilizer set to increase threefold by 2050, investigating the effects of fertilizers on the soil and its inhabitants is of paramount importance.
The rhizosphere—the interface between soil and roots—is a bustling place of interaction between roots and fungal and bacterial communities, with mutual beneficial or detrimental effects. A team of researchers led by Dr. Chanyarat Paungfoo-Lonhienne from the University of Queensland sampled the soil and rhizosphere of sugarcane crops before applying different doses of nitrogen fertilizer to the two halves of each sample field (200 kg N ha−1 y−1 versus 40 kg N ha−1 y−1).
Their research showed that while the number of different fungal taxa was the same for both halves of each crop, the composition of the fungal community was different. While Basidiomycetes fungi, which are lignin decomposers and therefore important for the carbon cycle, are more present in low-nitrogen soil, fungal genera which do not have a positive effect in plant or soil health were more abundant in high-nitrogen samples.
In short, the genera which most benefited from by high doses of nitrogen fertilizers were those which had a negative impact on soil and plant health, including many plant pathogens. Beneficial fungi were outcompeted in high-nitrogen environments.
When asked whether the beneficial fungi found in low nitrogen soil could outweigh or balance out losses in crop yield caused by low fertilizer usage, Dr. Paungfoo-Lonhienne replied: “We need to further investigate how those fungi effect crop growth. However, there are many studies showing that beneficial fungi, especially mycorrhizal fungi, are important contributors to soil function and nutrient delivery.”
The composition of rhizosphere communities is influenced by many factors such as plant species, crop cultivar, soil type, agronomical practices and so on. Being able to manipulate microbial communities that live in the rhizosphere of crop plants in ways that improves crop yields would reduce the need for synthetic fertilizers.
The article can be found at: Paungfoo-Lonhienne et al. (2015) Nitrogen Fertilizer Dose Alters Fungal Communities in Sugarcane Soil and Rhizosphere.
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Copyright: Asian Scientist Magazine; Photo: Rufino Uribe/Flickr/CC.
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