Lysimetry methods for monitoring soil solution electrical conductivity and nutrient concentration in greenhouse tomato crops

In intensive agricultural systems, such as Mediterranean greenhouses, monitoring soil nutrient and salt status is essential for optimising vegetable production and minimising soil and water pollution. This work analyses the dynamics of electrical conductivity (ECss) and nutrient concentration in soil solution collected simultaneously with various zero-tension lysimeters and a suction cup (a tension lysimeter) throughout two greenhouse tomato crops. The ECss obtained with zero-tension lysimeters (funnel and plate lysimeter) was generally lower than that with the suction cup, irrespective of soil depth. Moreover, the soil solution concentration of potassium, calcium, magnesium, sodium, chloride and sulphate obtained with funnel lysimeter (FullStop (TM)) was generally lower than that with suction cup throughout both cycles, while no clear differences were found for the nitrate concentration at 0.25 m depth in the 2013/14 cycle or at 0.38 m depth in the 2015 one. Overall, it appears that the soil solutions collected with the suction cup and the funnel lysimeter represent different soil solution status and processes. The funnel lysimeter collects freely draining soil solution, and it may therefore provide better information about the movement of elements between soil horizons, whereas the suction cup can sample soil solution from soil pores with longer residence times, especially under unsaturated flow conditions, and might represent better the available element concentrations for plant nutrition studies. The differential response found for nitrate could be due to the fact that it is a very mobile element within the soil. The soil water matric potential was slightly higher in the soil with zero-tension lysimeters throughout most of the 2013/14 cycle, and so these devices might alter soil solution movement and water and nutrient availability. On the other hand, in general, a good fit was found between the soil solution concentration of nitrate, potassium, calcium and sodium measured with a rapid analysis system (Laqua (TM)) and that measured using the reference laboratory method. This rapid system, in combination with the suction cup, can facilitate the farmers' control of soil nutrient and salt status. (C) 2016 Elsevier B.V. All rights reserved.