How Varying Nitrogen and Straw Depths Influence Paddy Field Ecosystems

Jenn Hoskins
19th March, 2024

How Varying Nitrogen and Straw Depths Influence Paddy Field Ecosystems

Image Source: Natural Science News, 2024

Key Findings

  • Study in Northeast China finds 150 genes involved in soil carbon cycle during straw decomposition
  • Moderate nitrogen application (130 kg hm^-2) optimizes straw-decomposing microbes and nitrogen cycling
  • Soil depth affects microbial community; best results at 0-15 cm depth with moderate nitrogen levels
Understanding how agricultural practices impact soil health is crucial for maintaining biodiversity and ecosystem services. A recent study from Yanbian University[1] has shed light on the effects of nitrogen (N) application rates and depths on the microorganisms that decompose straw in paddy fields, particularly in the cooler regions of Northeast China. This research is important as it helps to unravel the complex interactions between agricultural practices and soil microbial communities, which are essential for carbon and nitrogen cycling in the environment. Straw, often used as organic fertilizer, is returned to the soil to enrich it. However, the process of straw decomposition by soil microorganisms and how it's affected by different nitrogen application rates and depths was not well understood. The study from Yanbian University used advanced macro-genome sequencing technology to examine this process under various conditions. The researchers discovered that around 150 functional genes are involved in the carbon cycle during straw degradation. Notably, the methane production pathway involved the largest number of functional genes. In the nitrogen cycle, nitrogen fixation was prominent, with four types of functional genes identified. This finding is significant because methane is a potent greenhouse gas, and understanding its production in agricultural soils is essential for climate change mitigation. The study found that high nitrogen application rates (150 kg hm^-2) could inhibit carbon and nitrogen conversion processes. Interestingly, a moderate nitrogen application rate of 130 kg hm^-2 seemed optimal, maintaining a higher abundance of straw-decomposing microorganisms and nitrogen-cycling functional genes. Furthermore, the research indicated that the heterogeneity of the microbial community decreased with depth in the soil. After 71 days of straw return, the nitrogen cycling function declined, and some carbon functional genes increased with the depth of straw return. The microbial community structure and the abundance of functional genes involved in the nitrogen cycling process were more favorable at a depth of 0-15 cm with a nitrogen application rate of 130 kg hm^-2. This study expands on previous findings[2] that biochar, a form of organic amendment, can influence soil microbial communities over the long term. Similar to the effects of straw, biochar was found to alter the microbial community structure and increase microbial carbon use efficiency, which could lead to more stable soil organic matter. The current study builds on this understanding by exploring how nitrogen application rates and depths can further influence these microbial communities and their functions. The research also complements findings on the anaerobic oxidation of methane (AOM) by specific microorganisms[3], which is a critical process for controlling methane flux from anoxic environments. By identifying the genes involved in methane production during straw decomposition, the study contributes to a broader understanding of how agricultural practices may influence AOM and the broader nitrogen cycle. Moreover, the study aligns with the observation that microbial communities are affected by a range of factors, including soil pH, land use, soil type, and climate[4]. It confirms that nitrogen application rates and soil depth are additional important factors that can shape these communities and their ecological functions. In the context of global nitrogen cycle disruption due to intensive agriculture[5], understanding how to optimize nitrogen application to support beneficial soil microbes is more important than ever. The findings from Yanbian University offer practical insights for farmers in cool regions, suggesting that moderate nitrogen application rates and shallow incorporation of straw can create the best conditions for soil health and nutrient cycling. In conclusion, the study from Yanbian University provides valuable information on how to manage straw decomposition in paddy fields for better soil health and ecosystem functioning. It highlights the intricate relationships between agricultural practices and soil microbial communities that are essential for sustaining the delicate balance of carbon and nitrogen cycles in our environment.

EnvironmentPlant ScienceAgriculture

References

Main Study

1) Effects of different nitrogen applications and straw return depth on straw microbial and carbon and nitrogen cycles in paddy fields in the cool zone.

Published 18th March, 2024

https://doi.org/10.1038/s41598-024-56481-9


Related Studies

2) Biochar decreased microbial metabolic quotient and shifted community composition four years after a single incorporation in a slightly acid rice paddy from southwest China.

https://doi.org/10.1016/j.scitotenv.2016.07.135


3) Anaerobic oxidation of methane coupled to nitrate reduction in a novel archaeal lineage.

https://doi.org/10.1038/nature12375


4) Multi-factorial drivers of ammonia oxidizer communities: evidence from a national soil survey.

https://doi.org/10.1111/1462-2920.12141


5) The evolution and future of Earth's nitrogen cycle.

https://doi.org/10.1126/science.1186120



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