Soil properties modulate the effect of different carbon amendments on growth and phosphorus uptake by cucumber plant

Aim of study: Phosphorus (P) is a non-renewable, limited and strategic resource, inefficiently used in agriculture. Organic carbon (C) supply to soil can stimulate microbial activity increasing the mobilization of soil P thus improving its uptake by crops. This work aimed at investigating the effect of different C amendments on P uptake and how may differ depending on soil properties and P fertilization. Area of study: Soils used in this study were collected in SW Spain. Material and methods: An experiment with cucumber was performed involving three factors: (i) C amendment (cellulose, glucose, citric acid and control without amendment), (ii) soil type (Vertisol and Alfisol), and (iii) P supply (unfertilized, and mineral phosphate in form of KH2PO4). Main results: Cellulose or glucose provided the highest P uptake by plants in soils independently of the treatment. Cellulose and glucose addition was effective increasing dry matter (DM) in the Alfisol. Citric acid application decreased the development of aerial parts and roots, and P uptake in soils compared with other sources. In the Alfisol, increased P uptake with cellulose was associated to an increased concentration of low molecular weight organic acids, which seemed to be related to microbial activity. Research highlights: Organic amendments affect microbial activity, and P mobilization mechanisms are associated to microorganisms. This explain the improvement of P supply to plants with amendments; these effects, however, are modulated by soil properties and consequently vary depending on soil type.