The effect of sample positioning for quantification of residual N-NO3 in soil was determined after cultivating fertirrigated tomato plants. Three experiments were carried out in an unheated greenhouse, using drip fertirrigation. Soil N-NO3 level was determined from samples taken at the end of the cycle of each experiment. In all the experiments, the residual N-NO3 level of the soil was proportional to the amount of N applied in different criteria. Under unheated greenhouse conditions and using nitrogen fertilization by drip fertirrigation, the best soil sampling strategy for residual N-NO3 level determination was obtained by the use of a composite sample taken at a position 10 cm from the plants, between rows, and on the transplant row.
Lycopersicon esculentum; soil sampling; fertirrigation
