Nitrogen fertilisers in sugarbeet spring sowing : use of the spad optical instruments
2000
Tugnoli, V. | Bettini, G. (Associazione Nazionale Bieticoltori, Bologna (Italy))
The Spad or N-tester is a portable instrument that gives an optical determination of the quantity of chlorophyll present in leaves, thus enabling a rapid evaluation of the N-nutritional status of sugar beet during the vegetative stages (6 to 8 leaves). From the results of experimental plot trials conducted by the Technical Service of the National Beet Growers Association (ANB), there emerges a regression line showing a substantial correlation between the final nitrogen content in leaves as determined by the Kjeldahl method and the indication provided by the optical instrument. The findings of the tests have also made it possible to identify threshold rates for the application of N fertilizers (typically 0-60 units of nitrogen per hectare) at the 8-leaf vegetative stage.
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