Using nitrogen and sulphur for the poppy (Papaver somniferum L.) nutrition

The pot trial was carried out to estimate the effect of interaction of nitrogen and sulphur fertilization on seed yield, number of capsules per plant and concentration of morphine in the poppy straw (i.e. empty capsule + 15 cm of the stem) of the variety Opál. The natural content of sulphate sulphur in the soil was 18.3 mg S-SO4·kg of soil. The respective variants were supplied with ammonium sulphate (20,5% N and 24% S) to the level of 40 mg S-SO4·kg of soil. Nitrogen fertilization was applied in three doses: 0.3, 0.6 and 0.9 g N·pot. Nitrogen was made up to the appropriate level with ammonium nitrate (34.5% N). Fertilizers were applied in one single application after the emergence of the plant. The increase in seed yields in all the fertilized variants was statistically highly significant, i.e. by 54.8–143.7%, compared to the unfertilized control, and the yields increased with the higher doses of nitrogen. The increase in the level of sulphate sulphur in soil from 18.3 mg S-SO4 (control) to 40 mg S-SO4 resulted in a statistically significant increase in yields by 12.6%, but only in conjunction with the lowest dose of nitrogen (0.3 g N·pot). In the other variants the joint application of nitrogen and sulphur had no statistically significant effect compared to the same variants without sulphur. A statistically significant increase in the number of capsules per plant was seen with increasing N doses, in the fertilized variants ranging between 1.0 and 2.2 capsules per plant, compared to 1.0 per control plant. Irrespective of sulphur content in the soil, the highest number of capsules per plant (2.11 and/or 2.20) was noticed in the variants fertilized with the highest dose of nitrogen (0.9 g N·pot). The concentration of morphine alkaloid of in the poppy straw of the fertilized variants varied only a little, i.e. 0.63–0.76%, compared to 0.61% in the control. The highest dose of N resulted in the highest morphine concentration; sulphur showed no major effects.