Potato tuber quality improvement through nitrogen management optimisation: Review of methodologies

The respect of European legislation on nitrate leaching should force potato farmers not to apply nitrogen to the point where the maximum yield is attained. Therefore nitrogen fertiliser optimisation should aim at the application of the minimum N amount necessary to maximise the income, within these constraints. This implies that a high priority should be given to the improvement of tuber quality. Many tuber quality attributes are promoted by an adequate N supply, but decreased by an excess. High N applications tend to reduce crisping and frying quality and storability. Dry matter concentration is also slightly reduced with high N levels. Nitrogen deficiency, in addition to causing yield decreases, also affects tuber number and size distribution. Regulating nitrogen fertilisation in order to optimise yield and quality is difficult due to the number of soil, climate and plant factors that vary during the growing season. It has been shown that the best strategy is to split the nitrogen applications, giving initially to the crop a fraction of the optimal N dose calculated according to a balance method. Crop N status monitoring is then required in order to assess whether it is necessary to complement the dose with a second dressing. Several methods are available to monitor crop nitrogen status and they will be reviewed considering their limitations and potential.