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. 2025 Apr 25;14(9):1302.
doi: 10.3390/plants14091302.

Long-Term Effects of Nitrogen and Lime Application on Plant-Microbial Interactions and Soil Carbon Stability in a Semi-Arid Grassland

Kwenama Buthelezi  1 , Nkosinomusa Buthelezi-Dube  1
Affiliations

Long-Term Effects of Nitrogen and Lime Application on Plant-Microbial Interactions and Soil Carbon Stability in a Semi-Arid Grassland

Kwenama Buthelezi et al. Plants (Basel). .

Abstract

This study investigated the long-term (70 years) effects of N fertilisation (ammonium nitrate [AN], ammonium sulphate [AS]) at 70 and 211 kg N kg/ha, and liming (L) on plant-microbial interaction and soil carbon stability in a semi-arid grassland in South Africa. Aboveground biomass increased with N addition, particularly AN211, showing a 119% increase compared to the control, while both liming and N applications increased belowground biomass. Nitrogen addition significantly altered plant stoichiometric ratios, with root N ratios showing greater treatment-induced variation (12.7-51.3) than shoot N ratios (10.2-16.8). Microbial biomass carbon peaked with AN70 treatment, while dehydrogenase activity was highest in lime-only plots but suppressed in non-limed N treatments. Conversely, urease activity was highest in the control group and suppressed in most fertilised treatments. Despite increased biomass production, SOC remained unchanged across treatments (49.7-57.6 g/kg), whereas soil pH was lowest (<3.5) and highest (>6) under N fertilisation and lime, respectively. PCA revealed distinct clustering of treatments, with N forms differentially affecting plant allocation patterns and microbial parameters. This study demonstrates that plant-soil-microbe stoichiometric imbalances and pH-induced limitations on microbial function explain the disconnect between plant productivity and carbon sequestration in this semi-arid grassland ecosystem.

Keywords: carbon sequestration; nitrogen fertilisation; plant stoichiometry; soil microbial activity.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Response of the shoot and root C:N ratio to different liming and N additions. Means represented by same letter are not significantly different (p < 0.05) according to Tukey’s LSD procedure. C = control (0 kg/ha), L = lime (2250 kg/ha), AS70 = ammonium sulphate at 70 kg/ha; AS211 = ammonium sulphate at 211 kg/ha; AN70 = ammonium nitrate at 70 kg/ha; AN211 = ammonium nitrate at 211 kg/ha; AS70L = ammonium sulphate at 70 kg/ha + lime; AS211L = ammonium sulphate at 211 kg/ha + lime; AN70L = ammonium nitrate at 70 kg/ha + lime; and AN211L = ammonium nitrate at 211 kg/ha + lime.
Figure 2
Figure 2
Responses of shoot and root N:P ratio in different treatments. Means represented by same letter are not significantly different (p < 0.05) according to Tukey’s LSD procedure. C = control (0 kg/ha), L = lime (2250 kg/ha), AS70 = ammonium sulphate at 70 kg/ha; AS211 = ammonium sulphate at 211 kg/ha; AN70 = ammonium nitrate at 70 kg/ha; AN211 = ammonium nitrate at 211 kg/ha; AS70L = ammonium sulphate at 70 kg/ha + lime; AS211L = ammonium sulphate at 211 kg/ha + lime; AN70L = ammonium nitrate at 70 kg/ha + lime; and AN211L = ammonium nitrate at 211 kg/ha + lime.
Figure 3
Figure 3
Soil pH and soil organic carbon after 70 years of lime and nitrogen addition (adapted from Buthelezi and Buthelezi-Dube, 2022). Means represented by same letter are not significantly different (p < 0.05) according to Tukey’s LSD procedure. C = control (0 kg/ha), L = lime (2250 kg/ha), AS70 = ammonium sulphate at 70 kg/ha; AS211 = ammonium sulphate at 211 kg/ha; AN70 = ammonium nitrate at 70 kg/ha; AN211 = ammonium nitrate at 211 kg/ha; AS70L = ammonium sulphate at 70 kg/ha + lime; AS211L = ammonium sulphate at 211 kg/ha + lime; AN70L = ammonium nitrate at 70 kg/ha + lime; and AN211L = ammonium nitrate at 211 kg/ha + lime.
Figure 4
Figure 4
Microbial biomass carbon after 70 years of nitrogen and lime application. Means represented by same letter are not significantly different (p < 0.05) according to Tukey’s LSD procedure. C = control (0 kg/ha), L = lime (2250 kg/ha), AS70 = ammonium sulphate at 70 kg/ha; AS211 = ammonium sulphate at 211 kg/ha; AN70 = ammonium nitrate at 70 kg/ha; AN211 = ammonium nitrate at 211 kg/ha; AS70L = ammonium sulphate at 70 kg/ha + lime; AS211L = ammonium sulphate at 211 kg/ha + lime; AN70L = ammonium nitrate at 70 kg/ha + lime; and AN211L = ammonium nitrate at 211 kg/ha + lime.
Figure 5
Figure 5
Urease (a) and dehydrogenase (b) activity following 70 years of nitrogen and lime application. Means represented by same letter are not significantly different (p < 0.05) according to Tukey’s LSD procedure. C = control (0 kg/ha), L = lime (2250 kg/ha), AS70 = ammonium sulphate at 70 kg/ha; AS211 = ammonium sulphate at 211 kg/ha; AN70 = ammonium nitrate at 70 kg/ha; AN211 = ammonium nitrate at 211 kg/ha; AS70L = ammonium sulphate at 70 kg/ha + lime; AS211L = ammonium sulphate at 211 kg/ha + lime; AN70L = ammonium nitrate at 70 kg/ha + lime; and AN211L = ammonium nitrate at 211 kg/ha + lime.
Figure 6
Figure 6
Principal component analysis biplot showing relationships between plant, soil, and microbial parameters after 70 years of lime and nitrogen application. C = control (0 kg/ha), L = lime (2250 kg/ha), AS70 = ammonium sulphate at 70 kg/ha; AS211 = ammonium sulphate at 211 kg/ha; AN70 = ammonium nitrate at 70 kg/ha; AN211 = ammonium nitrate at 211 kg/ha; AS70L = ammonium sulphate at 70 kg/ha + lime; AS211L = ammonium sulphate at 211 kg/ha + lime; AN70L = ammonium nitrate at 70 kg/ha + lime; and AN211L = ammonium nitrate at 211 kg/ha + lime.
Figure 7
Figure 7
Location of Ukulinga grassland experiment site [48].
See this image and copyright information in PMC

References

    1. Zechmeister-Boltenstern S., Keiblinger K.M., Mooshammer M., Peñuelas J., Richter A., Sardans J., Wanek W. The application of ecological stoichiometry to plant–microbial–soil organic matter transformations. Ecol. Monogr. 2015;85:133–155. doi: 10.1890/14-0777.1. - DOI
    1. Tong R., Ma C., Lou C., Yuan W., Zhu N., Wang G.G., Wu T. Leaf nitrogen and phosphorus stoichiometry of the halophytes across China. Front. Plant Sci. 2023;14:1276699. doi: 10.3389/fpls.2023.1276699. - DOI - PMC - PubMed
    1. Dijkstra F.A., Pendall E., Morgan J.A., Blumenthal D.M., Carrillo Y., LeCain D.R., Follett R.F., Williams D.G. Climate change alters stoichiometry of phosphorus and nitrogen in a semiarid grassland. New Phytol. 2012;196:807–815. doi: 10.1111/j.1469-8137.2012.04349.x. - DOI - PubMed
    1. LeBauer D.S., Treseder K.K. Nitrogen limitation of net primary productivity in terrestrial ecosystems is globally distributed. Ecology. 2008;89:371–379. doi: 10.1890/06-2057.1. - DOI - PubMed
    1. Vargová V., Kanianska R., Kizeková M., Šiška B., Kováčiková Z., Michalec M. Changes and Interactions between Grassland Ecosystem Soil and Plant Properties under Long-Term Mineral Fertilization. Agronomy. 2020;10:375. doi: 10.3390/agronomy10030375. - DOI

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