METHODS TO DETERMINE NITROGEN IN SUNFLOWER GRAINS

Resumo

In sunflower, grain oil concentration (O_G) determines oil industrial yield and protein concentration (P_G) determines the protein of by-products as pellets and meals (P_M). There are various methodologies to quantify total grain nitrogen concentration (N_G): a) Kjeldahl (wet digestion); b) Dumas (dry combustion); c) NIRS (analysis of the spectrum of the light reflected by the sample). NIRS represents a promissory method for determining N_G because it is simple and fast. The objective of this work was to compare the methods of NIRS, Kjeldahl and Dumas to quantify N_G in sunflower grains and to adjust models to estimate P_M from N_G.

Eighty-four samples of sunflower grains were selected covering a wide range of variation in N_G (from 1.75 to 3.80 % taking Dumas reference) from a net of experiment conducted in southeastern Buenos Aires Province (2013-2014 and 2014-2015). NIRS was the most precise method for the determination of N_G and presented a greater degree of agreement with Dumas regarding Kjeldahl. P_M was satisfactorily estimated with N_G. Therefore, NIRS could be a superior alternative to the other techniques because presents low cost, it is fast, no toxic and has the advantage of being able to determine other components of the grain simultaneously with the determination of N_G