Assesing the vertical movement of a nematicide in a sandy loam soil and its correspondence using a numerical model (HYDRUS 1D)

Abstract

A test under laboratory conditions was performed to typify and model the vertical movement of a nematicide (DiTera) applied at concentrations of 400, 700, and 1000 mg L-1 via drip irrigation to a sandy loam class soil confined in tanks of 1 m(3). Vacuum extractometers were set up in the tank at different depths to obtain samples of soil solution starting 10 cm away from the drip emitter. HPLC was used to measure the nematicide concentration in the soil solution. Later HYDRUS 1D was used to model the vertical nematicide concentration considering homogeneous soil. Soil hydraulic parameters were obtained from laboratory experiments whereas the dispersion length was obtained by inverse estimation matching measured and modeled data. Laboratory results showed no significant differences in vertical nematicide (distribution considered a fraction of the initial concentration), having a higher concentration at the surface and decreasing gradually with the depth. The predictive model was able to describe te nematicide behavior of the nematicide according to controlled test, obtaining a R-2 of 0.97, a RMSE of 67.41 mg L-1, a RRMSE of 13.33% and a Nash of 0.92. These results confirm the proposed model; however, further studies on this issue are needed, considering different scenarios in laboratory conditions and thus scaling it up to field conditions.