Effects of nitrogen stabilizers and crop rotation on mineral nitrogen, N cycle genes and microbial community structure and abundance in podzolic soil in boreal climate

Mushtaq, Irfan (2022) Effects of nitrogen stabilizers and crop rotation on mineral nitrogen, N cycle genes and microbial community structure and abundance in podzolic soil in boreal climate. Masters thesis, Memorial University of Newfoundland.

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Abstract

Nitrogen (N) is an essential macronutrient required to enhance crop growth and yield. Excessive N application can result in N losses through nitrate leaching and denitrification which can be greater than 50% of applied N. Nitrogen losses can be minimized by application of synthetic N stabilizers and crop rotation that can inhibit volatilization, nitrification and denitrification processes for a few weeks and affect the N mineralization. Field experiment was conducted to investigate the effect of N stabilizers and crop rotation on soil pH, soil mineral N, genes involved in nitrification and denitrification process and the microbial community structure. The experiment was conducted in a randomized complete block design (RCBD) with split plot arrangement and replicated four times with plot size 3 m × 4 m. Experimental treatments were crop rotations (silage corn-silage corn, silage corn-wheat, silage corn-faba bean) and five nitrogen stabilizers and fertilizer (control, urea, agrotain, entrench, and super-U). N stabilizers significantly reduced the gene abundance involved in nitrification (amoA AOB, amoA AOA, nxr), and denitrification (nirK and nosZ) compared to plots treated with urea. N stabilizers had no significant effect on soil NH₄⁺ and NO₃⁻ as compared to urea. The results further revealed that N sources had no significant effects on fungal and bacterial community structure and abundance. However, crop rotation significantly affected both fungal and bacterial community composition and fungal Shannon diversity in boreal climate. Overall, cereal-legume rotation significantly affected the soil microbiome during nitrification and denitrification processes in boreal climate. Further, long term studies are required to determine the effects of N sources and crop rotation on microbiome diversity and abundance in boreal climate.

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