Trifluralin leaching in soils cultivated with sugarcane irrigated by sub-surface drip sistem

Abstract

In order to assess the movement of trifluralin in soils, used as root intrusion inhibitor in sub-surface drip irrigation system (SDI), its concentration at effluent from lysimeters was measured. The lysimeters with sugarcane (Sacharum officinarum L.) under natural weather conditions and supplementary irrigation were filled with two Oxisols and an Ultisol. Three lysimeters with undisturbed soil were used as replicates for each treatment; the columns were one meter in diameter and 45cm deep. The SDI system consisted of drippers installed at 20cm depth, with 10.5mm internal diameter tubing with 6 emitters per lysimeter spaced 50cm between them. A moisture sensor was installed in each lysimeter to monitor the soil water tension. A weather station was installed besides the lysimeters, in order to supply weather information. Precipitation, volume of leachate, and trifluralin concentration in the effluent were measured during 65 days. There was no change on the SDI system flow rate. The LVA presented the highest amounts of leached compound, which was above the EPA limit and lower than the allowed by Brazilian law.