Effect of deficit irrigation on nitrogen accumulation and capsaicinoid content in Capsicum plants using the isotope 15N

Greenhouse production of chilies requires constant irrigation and fertilization. Due to climate change, water availability is decreasing, and thus new techniques are being developed, one of which is deficit irrigation, also applied in controlled conditions, such as greenhouse production This allows us to improve yield quality with minimal or no reduction in yield with optimal water use. Nitrogen is an important macronutrient whose uptake can be hindered under deficit irrigation because deficit is a form of drought stress. In the pot experiment, two chili cultivars were tested to see how they responded to water deficit irrigation treatments compared to the field capacity treatment with peat substrate. Nitrogen fertilization, with the addition of the isotope 15N, was applied to all treatments. Seeds and leaves contained the most total nitrogen in both cultivars, followed by placenta. N utilization from fertilization was 3.32% at field capacity and 2.33% under deficit irrigation in 'Chili-AS Rot'. 'Naga Morich' utilized 4.58% of N from fertilizer under field capacity and 6.72% under deficit irrigation. Capsaicinoid content was strongly correlated with nitrogen content in both cultivars irrespective of irrigation regime. This study fills an important gap in our understanding of N assimilation, fertilization, and irrigation in chili plants. It shows that there is no universal rule for N absorption under different irrigation conditions in chili plants and that the right choice of cultivar and species is crucial for optimal and high-quality chili fruit production.