Abundance of Nitrogen Cycling-related Genes in Soil with Different Fertilization Levels

Abstract

This thesis emphasizes microbial community composition, nitrogen cycling composition, nitrogen cycling genes (nirK, nirS, and nifH), and microbial diversity in silty and sandy soils. It investigates the effects of NPK (Nitrogen, Phosphorus, and Potassium) fertilization on the soil microbiome. The study examined the structure of the microbial community in response to fertilization and evaluated the abundance of nitrogen-cycling genes using quantitative PCR (qPCR) and DNA metabarcoding techniques.

Fertilization may not directly change the functional capacity of nitrogen cycling in these soils, as the results showed that fertilization had no discernible effect on the overall abundance of nitrogen cycle genes. On the other hand, notable alterations in the composition of the microbial community were noted, with fertilization favoring specific taxa, especially those related to the nitrogen cycle process, such as Alcaligenaceae and Chitinophagaceae. The microbial community’s ability to adapt to low-nutrient situations was demonstrated by the higher prevalence of Acidobacteriota in unfertilized soils, a group generally linked to nutrient-poor circumstances.

Additionally, the study discovered that soil type had a more significant impact on microbial diversity than fertilizer. In contrast to sandy soils, silty soils showed higher microbial richness, highlighting the influence of soil properties like texture and organic matter concentration on microbial communities. These results imply that although fertilization modifies the composition of microbial communities, soil characteristics continue to play a significant role in microbial diversity.

The study also pointed out possible functional ramifications, pointing out that the fertilizer may increase nitrogen loss through denitrification and nitrate leaching, which, over time, may lower soil fertility. Fertilization increases production in the short term, but if not managed correctly, it can cause long-term environmental problems such as nutrient runoff and water resource contamination.

The study concludes that careful fertilization management is necessary to ensure long-term soil health and sustainability. Taking into account both soil parameters and the response of the microbial communities and how they react to different fertilization regimes may be possible through future studies employing modern techniques like metagenomics and metatranscriptomics.