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Research article - Peer-reviewed, 2013

Availability of phosphorus in greenhouse cropping systems with tomatoes - influence of soil and citric acid

Båth, Birgitta; Otabbong, Erasmus


Analyses of plant sap from organic greenhouse tomato crops show that the levels of phosphorus (P) are frequently low, despite the fact that soil analyses indicate P status in the soil to be good. In the present study, two soils (A and B) with a pH of just over 6 and a high total content of N and P were investigated with respect to release of P and uptake in a tomato crop. The fertilisers primarily used on soil A was silage and blood meal, and on soil B Vinasse and blood meal. An incubation experiment showed that the release of P per unit time was greater from soil A than soil B. This difference between the two soils may be due to lower soil organic matter concentration, with less P sorbed by Al and Fe on soil A, and a fertiliser regime which favours a high concentration of dissolved organic carbon in this soil. Tomato plants grown for 10 weeks in the soils had greater DW production, total uptake of P and concentration of P in the leaves on soil A than on soil B. Addition of citric acid to the soils in order to mobilise P increased plant yield and uptake of N and P on soil A. Despite the increased growth, the concentration of P in plant leaves increased and the N concentration was unchanged. On soil B addition of citric acid decreased Zn uptake in the tomato plants despite good availability, resulting in a lower concentration of this micronutrient in the leaves. The plants on soil A maintained their concentrations of all micronutrients analysed, but the ratio of P to micronutrients increased. Thus for commercial organic tomato growers, adding citric acid with the irrigation water offers a possibility to increase P availability.


phosphorus; nitrogen; micronutrients; tomato crop; Solanum lycopersicum mill; citric acid Introduction For the past ten years, a participatory research group in central Sweden has been working on issues relating to organic production of greenhouse tomatoes. An important issue for the growers in the group is to have a fertilisation strategy that prevents nutrient deficiency developing in the crop. Analyses of plant sap from existing commercial crops show that the levels of phosphorus (P) are frequently low (Magnusson et al. 2010), despite the fact that soil analyses indicate P status in the soil to be very good. Phosphorus can be easily fixed in soils, primarily by sorption

Published in

Acta Agriculturae Scandinavica, Section B - Soil and Plant Science
2013, volume: 63, number: 6, pages: 483-488

Authors' information

Båth, Birgitta
Swedish University of Agricultural Sciences, Department of Crop Production Ecology
Otabbong, Erasmus
Swedish University of Agricultural Sciences, Department of Soil and Environment

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