Effect of Irrigation Levels on Dissolved Organic Carbon Soil Distribution and the Depth Mobility of Chlorpyrifos

Julio Junod1*, Erick Zagal2, Marco Sandoval2, Ricardo Barra3, Gladys Vidal3, and Mario Villarroel4

Water flows provided by irrigation systems may be associated with dissolved organic carbon (DOC) content in the soil solution and may modify the mobility of pesticides, such as chlorpyrifos (CHP). These compounds were analyzed under field conditions, evaluating their distribution in the soil profile under excessive irrigation in a Humic Haploxerand soil. The trial was carried out in soil columns located under the canopy of apple trees (Malus domestica Borkh.) in an orchard located in the Bío-Bío Region, Chile. The insecticide CHP was applied 120 g hL-1, and later the natural run off was collected from the foliage to the columns. Surface irrigation was used as a control, the equivalent to 4 L h-1 weekly, plus two treatments over the columns of 6 and 8 L h-1 per pulse, respectively. Samples were obtained at three column depths: 0-5, 5-20 and 20-30 cm. The results showed that in spite of the fact there was no interaction between depth and irrigation, a greater concentration of CHP was observed in the samples with greater water flow, with significant differences between the treatments at a depth of 20-30 cm, which suggests some level of influence on vertical mobility. DOC shows stratification with greater concentrations at the surface and lower concentrations at depth, with significant differences between the superficial stratum (0-5 cm) and the lower strata (5-20, 20-30 cm). These results are discussed in relation to explaining the movement of CHP in the soil profile.

Keywords: pesticides, organic matter, volcanic soil.
1 Universidad del Bío-Bío, Facultad de Ciencias de la Salud y los Alimentos, Casilla 474, Chillán, Chile. *Corresponding author (jjunod@ubiobio.cl)
2 Universidad de Concepción, Facultad de Agronomía, Av. Vicente Méndez 595, Casilla 537, Chillán, Chile.
3 Universidad de Concepción, Centro EULA, Víctor Lamas 1290, Casilla 160 C, Concepción, Chile.
4 Universidad de la Frontera, Facultad de Ingeniería, Francisco Salazar 01145, Casilla 54 D, Temuco, Chile.