Effect of wetting agent on fertigation parameters and pollution in melon growing in new and reused coco fiber

Wetting agents or surfactants reduce surface tension of water and have been used to improve wettability, water-air relations and nutrient availability to crops grown in inorganic substrates. Re-use of substrates have some problems about capability to absorb water. Also majority of the horticulture production systems in soilless culture are open systems in which the nutrient solution of leaching is thrown away to soil resulting in pollution. This study was conducted to improve air-water relations with a wetting agent in melon crop on new and re-used rock wool as growing medium. The specific aim was to examine the influence of wetting agent in fertigation parameters and incorporation and emission to the environment of nutrients. Two experiments were conducted. New and re-used rock wool was used in the experiments 1 and 2 respectively. Both experiments had two treatments without (T0) and with wetting agent (T1). The surfactant was nonylphenol polyethylenglycol (20% w/v) and it was applied in drip irrigation (0.1%) once a week in the latest two irrigations of a day. Treatments were arranged on randomized blocks in both experiments. Irrigation and drainage volumes were measured weekly. Al2o electrical conductivity, pH, anions (NO₃, H₂PO₃-, SO₃ ²- and Cl^-) and cations (Ca², K⁺ Mg² and Na⁺) in irrigation water and drainages were determined. Finally percentage of drainage, water uptake and incorporation and emission of nutrients were calculated. The wetting agent increased incorporation of potassium and reduced emission of nitrate and potassium in reused coco fiber significantly. Water uptake and volume, electrical conductivity and pH of drainages were not affected by surfactant.