Effect of Top-fertilizing of Raw Protein and Glucosinolates Content of Winter Turnip Rape
Jõgeva Plant Breeding Institute, J.Aamisepa 1, EE48309 Jõgeva, Estonia;
Rapeseed is a major oil–yielding crop, ranking third place after soybeans and oil palm in the world. Rapeseed contains as average 36–38% crude protein and content of anti–nutritional compounds, among which glucosinolates have received the major attention. The object of the present study was to evaluate the effect of the nitrogen rate and different application times to the crude protein and glucosinolate content of winter turnip rape. The trials were carried out at the Jõgeva Plant Breeding Institute in the 2007–08, 2008–09 and 2009–10 growing seasons. Ammonium sulfate (nitrogen content 21%, sulphur 24%) was used as top–fertilizer. Three different nitrogen rates, 120, 140 and 160 kg N ha−1 and three different application times were used: A) once at the beginning of spring growth (oilseed rape growing code 26), B) A + when the main stalk was 10 cm (code 33), C) B + start of flowering (code 60) (a total of nine different variants) in equal portions. The results indicate that the quantity of the fertilizer has not as strong an impact as application time on the glucosinolate content. The lowest glucosinolate content was obtained from the variant of one N application. The highest protein content was obtained from the variant of three times split-N.