Solute Movement Patterns in Trickle Irrigated Tomatoes

Abstract

A study was conducted in a commercial drip irrigated tomato (var. Floradel) field to investigate fertilizer solute movement patterns in relation to dripper location. Six tomato plots were established, three of which were planted and the other three left fallow. Soil samples were taken at planting and after harvest at various locations from the dripper and were analyzed for electrical conductivity, pH, bicarbonate-extractable P, and ammonium acetate-extractable (IN, pH 7), K, Na, Ca, and Mg. All fertilizer was applied via drip irrigation. Considerable movement of P was observed throughout the soil profile possibly because of slow rates of calcium phosphate precipitation due to the low pH of the irrigation water and the possible presence of Mg⁺² and HCO₃^-1 in solution, and to the predominant movement of fertilizer solutions through soil macropores. Movement of K was less evident than that of P, but could have been masked by large plant uptake of K. Increases in electrical conductivity were most evident near the emitter and along the salt fringe at the edge of the wetting zone near the soil surface. Conductivity increased most in the latter zone, but never exceeded 0.8 mmhos/cm. Levels of P, K, and electrical conductivity at the end of the experiment were nearly always larger in the fallow plots than in the tomato plots, probably because of nutrient uptake by the tomato root system in the latter.