Effect of wetting agent on fertigation parameters in tomato on 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 on organic substrates. Used substrates have some problems about capability to absorb water. This study was conducted to improve air-water relations with a wetting agent in tomato crop on new and used coco fiber as growing medium. The specific aim was to examine the influence of wetting agent in fertigation parameters and incorporation-emission to the environment of nutrients. Two experiments were conducted: Experiment 1 about new coco fiber and Experiment 2 about reused coco fiber. Experiments both 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. Also were determined electrical conductivity, pH, anions (NO₃^-, H₂PO₄^-, SO₄^2- and Cl ^-) and cations (Ca²⁺, K⁺ and Na^-) in irrigation water and drainages. Finally were calculated percentage of drainage, water uptake and incorporation and emission of nutrients. The wetting agent increased percent of drainage and reduced water uptake significantly. Electrical conductivity and pH of drainages, as well as incorporation and emission of anions and cations were not affected by surfactant, with the exception of sulphates in new coco fiber with an increment of 9.2 %. It proves that the surfactant could improve the efficiency of water use and not increase the environmental pollution with anions.