The decline of soil fertility due to intensification of agricultural practice can lead to reduced plant performances; the use of organic amendments could be a valuable strategy to overcome this this problem. The aim of the present study was to verify that the application of organic fertilizers may promote root growth to the detriment of the canopy by evaluating the effects of application of organic fertilizer on CO2 fixation, C partitioning, and plant growth. The experiment was carried out on strawberry (Fragaria x ananassa) plants, potted in 10 L pots. The following treatments were compared, in a complete randomized block design: (1) unfertilized control; (2) mineral fertilization; (3) cow manure (20 g kg(-1) soil); (4) compost low rate (20 g kg(-1) soil); (5) compost high rate (60 g kg(-1) soil). Two months after their application, fertilizers did not affect plant growth; however, the application of compost at the high rate stimulated the (CO2)-C-13 assimilation. In the following 2 weeks, plants treated with compost at 60 g kg(-1) soil showed a higher amount of C-13 than the other treatments; however, the C-13 relative partitioning was not affected by fertilization. Root:canopy ratio was decreased by mineral and compost high rate fertilizations, in response to the increase of root N concentration, indicating that root growth was stimulated by low soil N.