Influence of foliar urea on the antioxidant response and fruit color of sweet pepper under limited N supply

Abstract

AbstractBACKGROUND: Foliar fertilizer methods could provide a rapid and efficient response when uptake by plant roots is limited. This work studies the effect of foliar urea sprays (15 g L−1) at different frequencies on the antioxidant metabolism and fruit quality of sweet pepper fruits under N‐limited nutrient solution (3.5 mmol L−1 NO3−) and fully N‐supplied (12.5 mmol L−1 NO3−) plants.RESULTS: Foliar applications of urea in root N‐limited plants increased the total N concentration in the fruits and no significant differences were found with respect to control fruits (plants fully supplied with N by the roots). Fruit color was significantly affected by the urea sprays, and at the highest frequency (twice a week) the largest overall color difference (ΔE) with respect the non‐sprayed fruits was obtained. Foliar urea increased anthocyanin concentration to control values but flavonoids were only affected at the highest application frequency. N deficiency induced oxidative stress but foliar application of urea altered this response, significantly diminishing catalase and ascorbate peroxidase activity.CONCLUSION: Sweet pepper fruits showed a significant and positive response to foliar fertilization on the studied parameters, compensating to a major extent the reduction of N by the roots. In addition to the environmental issues in reducing N contamination, fully monitored automatically sprayed foliar fertilizer could utilize N more efficiently and at lower cost than applying the full recommended rate of other N fertilizers to the nutrient solution, providing flexibility in correcting N nutrition in the plant, and especially the control of nutrient supply independent of the water supply. Copyright © 2008 Society of Chemical Industry