Comparison of performance characteristics of methods for measurement of nitrogen content in plant leaves in a laboratory under accreditation to ISO/IEC 17025

Alona Telerman , Food & Health Division, Israel Laboratory Accreditation Authority (ISRAC), Airopot city, Israel (alonat@israc.gov.il)

The Israel Laboratory Accreditation Authority (ISRAC) is a statutory corporation established under the law of the Israel Laboratory Accreditation Authority, 1997. Its purpose is to provide recognition of the ability and professional competence of laboratories to perform tests in accordance with world standards, regulations, and other reference specifications. Certification process verifies that the organization is authorized to perform in a professional and reliable testing as specified by the scope submitted by the organization and approved by ISRAC. The accredited laboratories perform tests in many fields such as chemistry, construction, electronics, and medicine. One of these laboratories is Agri I.O.T Group LTD, which has developed bio-optic unique application, Croptune, that helps growers optimize fertilizer application. Croptune determines the crop's nutritional status, instantly detects deficiencies using a standard smartphone camera. Nitrogen (N) is a major element for plant growth and is a radical part of chlorophyl, which is the primary absorber of light energy needed for photosynthesis. The image is taken by smartphone is uploaded to the cloud and processed using a dedicated algorithm that gives as an output a value linked to the amount N and provides recommendations for fertilization. The laboratory calculated the uncertainty when validating the method. For metrological traceability and calibration of the method, the image-based data for N uptake were compared to results of the standard spectroscopic analysis done by another, reference laboratory. A correlation was demonstrated between the weight of N measured in chemical laboratory and estimated with the color camera (r² = 0.91).