The effect of different fertigation strategies on salinity and nutrient dynamics of cherry tomato grown in a gutter subirrigation system

The advantages of subirrigation for water distribution uniformity, water-saving, and other crop performances have been well documented in previous works. However, in subirrigated crops, an accumulation of salts inevitably occurs in the top layer of the growing medium, which represents one of the main difficulties to prolong the recirculation of the nutrient solution. Such an accumulation strongly depends on nutrient and non-nutrient (e.g., saline ions) concentrations, irrigation scheduling and water volumes and fluxes in the system. Tomato cherry plants (Solanum lycopersicum L. cv. Shiren) were grown soilless in a gutter subirrigation (closed-loop) system, during the spring season, to evaluate nutrient dynamics and crop response to: i) the nutrient solution concentration (i.e., standard and 50% reduced concentration), ii) irrigation frequency (i.e., high or low frequency), iii) irrigation duration (i.e., long or short time duration), and iv) tank volume at the refill (i.e., high and low volume). The most important factor, which influenced the nutrient dynamics and electrical conductivity of the system, was the concentration of the nutrient solution, followed at distance by the other three. The recirculated solution with reduced concentration showed a fairly stable composition (ranging from 1.2 to 1.6 dS m⁻¹ of the electrical conductivity in the worst factor combination) with the electrical conductivity of water extracts in the upper substrate layers below 2.0 dS m⁻¹ and the ratio between recirculated solution and plant uptake concentration of about 1 for most of the elements. Marketable fruit yield was 48% higher with the reduced concentration solution and affected by irrigation scheduling and tank volume at refill. By adapting the composition of the recirculated nutrient solution, to the available water quality and plant needs, a gutter subirrigation closed system can be safely managed for a short-cycle spring tomato crop.