ที่มา:วิทยาสารเกษตรศาสตร์ สาขา วิทยาศาสตร์

หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Correlation between Pummelo Leaf Nitrogen Concentrations Determined by Combustion Method and Kjeldahl Method and their Relationship with SPAD Values from Portable Chlorophyl

ผู้เขียน:Nopporn Jaroonchon, ดร.กฤษณา กฤษณพุกต์, รองศาสตราจารย์, ดร.ลพ ภวภูตานนท์, ผู้ช่วยศาสตราจารย์

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Abstract

Discrepancies in reports of leaf tissue nitrogen (N) concentrations are in part due to different analytical methods among laboratories. Two standard methods of N determination, the combustion method and the Kjeldahl method, were compared for pummelo [Citrus maxima (Burm. f.) Merr.] leaf N analysis. Pummelo plants were fertilized with different N rates and leaves with different ages were sampled to obtain various leaf N levels. Leaf greenness (SPAD value) of each sample was measured by a portable chlorophyll meter prior to nitrogen analysis. The results showed that N concentrations of pummelo leaf samples were in the range 1.23-2.54% using the combustion method and 1.00-2.08% for the Kjeldahl method. The combustion method yielded higher N concentration values than the Kjeldahl method in every sample. A linear relationship between the combustion and Kjeldahl N values was highly significant (Kjeldahl N (%) = 0.7829 ? Combustion N (%) + 0.1150; R2 = 0.86 and p-value < 0.0001). The addition of samples of pummelo fruit parts that had wider ranges of N concentrations (0.74-4.08% for the combustion method and 0.57-3.51 % for the Kjeldahl method) than leaf tissue into the analysis increased the coefficient of determination (Kjeldahl N (%) = 0.8676 ? Combustion N (%) – 0.0384; R2 = 0.96 and p-value < 0.0001). Therefore, comparisons and interpretation of pummelo leaf N analysis results from different laboratories should mention the analytical method used and provide a linear equation for adjusting the N values. In addition, SPAD values had a positive correlation with leaf N concentrations determined by both methods and could be explained by quadratic polynomial equations (Combustion N (%) = 0.0003 ? SPAD2 – 0.0313 ? SPAD+2.5024; R2 = 0.21 and p-value < 0.0001; Kjeldahl N (%) = 0.0004 ? SPAD2 – 0.0372 ? SPAD+2.4086; R2 = 0.16 and p-value < 0.0001). It is suggested that the SPAD value determined by a portable chlorophyll meter can be used to obtain a quick estimation of pummelo leaf N status.

Article Info

Agriculture and Natural Resources -- formerly Kasetsart Journal (Natural Science), Volume 044, Issue 5, Sep 10 - Oct 10, Page 800 - 807 |  PDF |  Page