Determination of Spatial Variability of Nutrient Composition of Soil Solutions in Greenhouses by Using Suction Cups

Abstract

The spatial variability of pH, EC and concentrations of K⁺, Ca²⁺, Mg²⁺, Na⁺, and Cl⁻ in the soil solution of a fertigated soil in a greenhouse was studied using suction cups. The considered factors that modify the composition of the soil solution were: soil depth (0.10 and 0.25 m), distribution of nutrients before and after irrigation, evolution during the growth cycle, and location inside the greenhouse. Each parameter was studied separately to determine its effect on the nutrient composition of the soil solution, and consequently to standardize the soil solution sampling and design of fertilizer applications.

Significantly higher levels of EC and concentrations of Mg²⁺, Na⁺, and Cl⁻ were found at 0.25 m, whereas higher concentrations of and K⁺ were obtained with suction cups in the topsoil horizon (0.10 m). Irrigation with nutrient solution modified the concentrations of and significantly, and during the growth period the concentrations of pH, and Na⁺ varied significantly. A simple linear model to estimate the actual soil solution composition from the soil moisture and previous soil solution composition was obtained, showing a close relationship with the experimental values found by means of suction cups after irrigation. This model can be of use in the calculation of the composition of optimized nutrient solutions by means of suction cups. This procedure can also be relevant in the design of optimized nutrient solutions for fertigation, maximizing plant production and minimizing excessive use of fertilizer and pollution in intensive horticultural ecosystems.

Keywords:

• Suction cups
• Soil nutrient solution bioavailability
• Strain gauges

Acknowledgments