The objective was the evaluation of nutrient losses to soil during horticultural plant cultivation in greenhouses where open fertigation systems are used. Losses were estimated by comparing the chemical composition of nutrient solution effluent from the drippers to the growing media with nutrient leakage from the media to the soil (called drainage or drainage waters) during soilless culture of tomato, cucumber, roses and gerbera. Largest losses were of potassium (up to 413 kg K/month/ha), nitrates (up to 231 kg NO₃-N/month/ha), calcium (up to 220 kg Ca /month/ha) and sulphur (up to 101 kg SO₄-S/month/ha). Smallest losses were of microelements (from 0.01 kg of Mn and Cu to 3.46 kg of Fe per month/ha). In Poland, the greatest horticultural pollution source for the environment is caused by the fertigation of tomato, whose cultivation area covers 2,500 ha, and whose production cycle lasts about 10 months. The least pollution arises from gerbera, which covers only about 90 ha. Sources of agricultural point pollution are generally attributed to animal farms. On the basis of the presented study the source of point pollution is not only assigned to typical agricultural production, but also to greenhouse production systems using soilless culture and open fertigation.