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

Abstract

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 that 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.

Solubility and Leaching Risks of Organic Carbon in Paddy Soils as Affected by Irrigation Managements

“…Higher WEOC contents in deep soils of 20–30, 30–40, and 40–60 cm in the FI fields indicate that more DOC was transferred from the topsoils to the deep soils due to high percolation rate (Table 2). The relationship between soil WEOC distribution in the soil profile and water flows was indicated by Mertens et al (2007) [55] and Junod et al (2009) [56] on arable soils. But DOC contents in deep soil solutions in NFI paddies were always lower than those in FI paddies (Figure 4).…”