CARBON AND NITROGEN ANALYSIS IN SOIL FOR SUSTAINABLE AGRICULTURE AND FARMING

04/14/2021

Learn about the importance of Carbon and Nitrogen determination in different soil types and discover the latest results obtained with the VELP CN 802 Elemental Analyzer as part of the Wepal International Proficiency Testing Program.

CARBON AND NITROGEN ANALYSIS IN SOIL FOR SUSTAINABLE AGRICULTURE AND FARMING

A healthy, high-quality soil functions as a vital living ecosystem that sustains plants, animals, and humans. This definition speaks to the importance of managing and taking care of the soil so it represents a sustainable resource for future generations.

Carbon and Nitrogen determination in Soil and Sediments

In which forms are Carbon and Nitrogen present in soil and sediments? Why are these elements so important concerning soil health?

Carbon is present in the soil in two different forms: inorganic and organic. Inorganic carbon consists of mineral forms of carbon, while soil organic carbon refers to organic compounds as plant and animal detritus, cells and tissues of soil microbes, and substances that soil microbes synthesize. In this respect, Total Organic Carbon determination (TOC) is important because high levels in soils prevent the anaerobic digestion process and limit the subsoils' nitrogen enrichment.

Nitrogen is a very important macronutrient for plant growth, plant food processing and the creation of chlorophyll and is rapidly cycled in the soil as decomposer microorganisms break down organic matter.

The links and interactions between Carbon and Nitrogen are extremely relevant when understanding different soil characterization and conditions. The Carbon-to-Nitrogen ratio (C:N ratio) is of primary importance because it has a direct impact on residue decomposition and nitrogen cycling in soils. The higher the ratio, the longer it takes for the material to decompose.

Likewise, the smaller the ratio is, the more rapidly the plant material will decompose. This also has a direct relationship with the amount of nitrogen that is tied up in the soil and that will be available to the next growing plant. The ratio 24:1 is the proper carbon and nitrogen that a microorganism must have to sustain its health.

By determining and monitoring soil Carbon-to-Nitrogen ratio and dynamics it is possible to assess soil quality and productivity indicators, ultimately making the right choices in terms of sustainable crops, rotation and Nitrogen fertilization. For instance, as farm managers it is critical to be aware of C:N ratio to plan proper rotations and to blend certain types of crops with others if needed to get close to the optimum C:N ratio of 24:1.

How to determine Carbon and Nitrogen in soil samples with VELP Elemental Analyzer

VELP CN 802 is a versatile, cloud-enabled and fully automatic combustion analyzer for simultaneous carbon and nitrogen determination in different organic matrices.

Ensuring high accuracy, improving sample throughput and requiring minimum maintenance, the CN 802 is the ideal solution for Total Carbon, Total Nitrogen and C:N ratio according to official methods for laboratories, research centers and Quality Control in the Agronomy, Environmental and Food & Beverage industries.

CN 802 analytical measurements are successfully evaluated every year by joining the Proficiency Testing Program organized by WEPAL (Wageningen Evaluating Programs for Analytical Laboratories).

Samples of different soils and sediments are received and analyzed using the CN 802 and the results obtained (C %, N % and TOC %) are successfully compared with the statistical range accepted by WEPAL.

Data from the analyses performed in 2019 and 2020, listed in the table below, show the good repeatability and accuracy of the CN 802.

Very different types of soil samples in terms of Carbon and Nitrogen values such as sediment river clay, clay soil or sandy soil were analyzed and all the results were successfully compared with WEPAL expected results.

Sample 2019-2020	Element %	VELP Results Average* %	WEPAL Assigned value % Xpt	WEPAL SD % s(Xpt)	Compliant with WEPAL
Sediment river clay	C	7.023	6.981	0.245	OK
	N	0.370	0.372	0.019	OK
	TOC	6.107	5.882	0.495	OK
Sediment	C	4,574	4,51	0.130	OK
	N	0.158	0.158	0.013	OK
	TOC	3.188	2.980	0.590	OK
Clay soil W-19	C	2.577	2.539	0.092	OK
	N	0.138	0.142	0.011	OK
	TOC	1.556	1.503	0.199	OK
Clay soil W-20	C	2.524	2.520	0.05	OK
	N	0.084	0.090	0.009	OK
	TOC	0.807	0.734	0.101	OK
Sandy soil W-19	C	1.762	1.724	0.105	OK
	N	0.111	0.109	0.009	OK
	TOC	1.705	1.667	0.153	OK
Sandy soil W-20	C	2.400	2.470	0.18	OK
	N	0.146	0.156	0.024	OK
	TOC	2.343	2.34	0.22	OK
Forest Sandy soil	C	5.006	5.224	0.620	OK
	N	0.152	0.168	0.023	OK
	TOC	5.193	5.119	0.854	OK
Calcareous soil	C	3.543	3.55	0.08	OK
	N	0.038	0.047	0.011	OK
	TOC	0.499	0.499	0.013	OK

*n=10

Find out more with the Application Notes

Discover the dedicated Application Note on Total Carbon, Nitrogen and TOC Determination in reference soils and sediment samples.
Download the Application Note >