In this study we hypothesized that the effect of nitrogen form well as light intensity on Ca content in the sweet pepper fruit may depend on stage of fruit maturity. Thus the effect of nitrogen form (100% N-NO₃ or 50% N-NO₃ + 13% N-NH₄ + 37% N-NH₂), type of polyethylene film covering the tunnel (two types of film, Ginegar or Gemme 4S, characterized by various PAR transmissions) and stage of fruit maturity on Ca and dry matter content in sweet pepper fruits were determined. Sweet pepper plants were cultivated in rockwool slabs. The chemical analyses were performed on sweet peppers harvested in five stages of growth and ripening, beginning with fruits of 2–4 cm diameter. Plants supplied with nutrient solution containing nitrate N form accumulated more Ca. The influence of film type covering the tunnel was unsystematic. Irrespective of N form and film type the contents of Ca and dry matter varied depending on fruit growth and ripening stages. Systematic increase in Ca accumulation occurred until reaching the stage of mature-green sweet peppers, while during further ripening the level of Ca decreased. The dynamics of dry matter accumulation were opposite to that of Ca. Additional determination of Ca was performed in mature green fruits, coming from nitrate N and Gemme 4S film (transmitted more light) treatment, both normal and with visible symptoms of blossom-end rot (BER). The analysis was conducted separately in the upper and lower part of fruits. Higher amount of Ca was found in the upper part in normal and BER fruits. Since BER was developed in fruits with Ca content in the lower part equaled to 0.60 mg∙g^-1 d.m., but in 2007 no symptoms of BER were noted in fruits contained only 0.38 mg∙g^-1 of Ca, other co-factors, not only low Ca level in fruit, should be considered in the prediction of BER.

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