Effect of magnesium and nitrogenous fertilisers on the growth and alkaloid content in Lupinus angustifolius L.

Abstract

The effect of kieserite (MgSO₄.H₂O) and nitrogenous fertilisers in various forms [control, Ca(NO₃)₂, (NH₄)₂SO₄, NH₄NO₃, CO(NH₂)₂] on the growth and alkaloid content in L. angustifolius was investigated. Mineral fertilisers were applied at doses of 60 kg/ha of Mg and 75 kg/ha of N before sowing. Kieserite did not have a significant influence on the growth and dry matter production of lupin. Ca(NO₃)₂ and NH₄NO₃, although increasing the yield of straw, did not affect the yield of seeds. The application of (NH₄)₂SO₄ decreased the yield of straw and seeds when compared with the effect of the above-mentioned fertilisers. The effect of Mg and nitrogenous fertilisers on alkaloid biosynthesis in vegetative organs depended, most of all, on the weather conditions in the vegetation period and on the developmental stage of lupin at which they were applied. At the stage of 6-7 leaves, the alkaloid content was negatively correlated with the content of Mg in plants (R² = 67%). The influence of mineral forms of nitrogen on the alkaloid content in the dry matter increased in the following order: (NH₄)₂SO₄ < NH₄NO₃ < Ca(NO₃)₂. The nitrogen fertilisers studied significantly modified the alkaloid content in the seeds, but the effect of nitrogen fertilisers also depended on Mg. In the treatments without Mg, nitrogenous fertilisers significantly increased the content of alkaloids by 9-17%. The greatest increase in alkaloid content was found when NH₄NO₃ was applied, followed by (NH₄)₂SO₄. Simultaneous application of Mg and nitrogen decreased the content of alkaloids in seeds, depending on the year of study, by 2-8%.