Nitrogen fertilization strongly influences shoot and root growth as well as yield, especially for Bell pepper (Capsicum annuum L.). Commercial bell pepper cultivars (Canon and Galliano) were assessed under various nitrogen fertilization regimes in a greenhouse condition to assess the possibilities of reducing nitrogen amounts. We studied above- and below-ground growth parameters by comparing the conservative approach of continuous fertilization to withholding fertilization for 30 and 60 days, and autonomic fertilization monitored by newly developed belowground nitrate sensors. Gas exchange, shoot and root morphology, mineral distribution in the leaves and yield were studied.
When fertilization was stopped for 60 days, gas exchange was significantly inhibited affecting the crop yield negatively. Withholding fertilization for 30 days, continuous fertilization and autonomic fertilization exhibited a similar positive trend in gas exchange and shoot morphological characteristics including yield. NF60 and CF exhibited yield difference among the two cultivars at the end of the growing season.
Total nitrogen and leaf petiole nitrate uptake were highly accumulated in NF30, CF and, AF whilst the C/N ratio increased for the 60 days fertilization stress only. This resulted in an increased root length, root volume and, root surface area in both cultivars for NF60.
Our results suggest that proper management of nitrogen fertilization through application regimes and even by halting fertilization for 30 days can positively enhance plant performance, optimize nitrogen use, minimize production cost, and maximize crop yield.