Soil solution distribution under subsurface drip fertigation determined using TDR technique

Abstract

The use of drip irrigation in agriculture is gaining more efficiency in the management of water and nutrients. The expansion of subsurface drip irrigation in the cultivation of sugarcane is demanding more information in this area of knowledge, for example, the behavior of ions in the wet bulb. Thus, the goal of this work is to evaluate the soil solution distribution using the TDR technique (Time Domain Reflectometry) in subsurface fertigation. The experiment was carried out in the greenhouse of the Department of Natural Resources and Environmental Protection - CCA/UFSCar. We used two PVC containers (500 L) filled with sandy soil, and, in each of them, one dripper installed at depth of 0.30 m. In the container we installed a mesh (6 x 6) of 36 TDR probes, spaced by 0.10 m, the layers being arranged at the following depths from the base of the container: 0.05; 0.15; 0.25; 0.35; 0.45 and 0.55, for automatic monitoring of electrical conductivity in order to determine the evolution and soil solution distribution along time. The treatments were based on flow rate (1.0 and 1.6 L h-1), applying each time 1.0 L of solution of potassium nitrate (KNO3) for a total of 10 applications at the end of each test. The results observed in the two treatments was a gradual distribution of soil solution with higher concentration of the solution near the dripper and also a greater tendency for horizontal displacement of the wetting front, with the solution over 0.30 m from dripper position.