Spatial distribution of plant protection products in soilless cultivation in a greenhouse and effect on emission to surface water

摘要

In soilless cultivation systems in greenhouses part of the surplus of nutrient solution given to the plants is discharged. The discharge contains nutrients and plant protection products (PPPs) which pollute the surface water. An experiment was set-upto determine the spatial distribution of PPPs in a greenhouse after spraying. Do PPPs enter the discharge flow after spraying and is it possible to influence the amount by better adaptation of the spray bar? It appeared that after spraying an old tomatocrop with the traditional vertical spray bar 30-50% of the applied dosage was found back on the substrate slabs and 10-25% on the ground. The amounts are very much influenced by the leaf area. Here the leaf area was rather low. Closing the lowest nozzlehighly affects the quantity reaching substrate and ground (only 10-25% on the substrate and 3-6% on the ground). Covering the slab opens possibilities to a further decrease of the amount entering the water flow. However, this means a new design of the troughs. It also appeared that even in a modern high greenhouse PPPs enter the condensation water. It was estimated that after each spraying a substantial part of the PPP will be discharged to surface water.