Soya bean, like other plants from the Fabaceae family, uses nitrogen from the air owing to its symbiosis with rhizobia. As a result, it does not require intensive fertilization with this element. A controlled  field experiment was conducted over 2012-2014 at the Experimental Station of Variety Testing in Przecław. The test plant was soya, cv. Aldana. The experimental factor consisted of nitrogen doses: 0, 30, 60, 30+30 kg ha-1. Nitrogen fertilization significantly diversified the seed yield of soya bean. A single application of the dose of 30 or 60 kg ha-1 increased the seed yield by 0.63 and 0.67 t ha-1, respectively, compared with the control. The highest increase in yield, by 1.21 t ha-1, was obtained after the application of nitrogen in two doses (30+30 kg ha-1). The plants from the control treatment (without nitrogen fertilization) were characterized by the smallest number of pods and TGW (Thousand Grain Weight). The use of nitrogen in two doses effected an increase in the SPAD index at 69 and 75 BBCH stages. Also, the SPAD index was observed to vary in the years of the study. High doses of nitrogen increased the content of total protein in seeds and decreased the content of crude fat, as well as causing a significant decrease in the content of ash and fibre in seeds compared with the control. The highest content of total protein was obtained in 2012 and the crude fibre content was the highest in 2014. Fertilization with nitrogen did not affect the concentration of macroelements, whereas it increased the content of iron (Fe) and decreased the content of copper relative to the control. The highest content of manganese in grains was obtained in the control and zinc was the highest in treatments with higher nitrogen doses. The content of macroelements and microelements in seeds was significantly diversified in the years of the study.

23.2.2018