Toward sustainable Brassica napus production: Optimizing fertilization regimes for yield, water, and nutrient efficiency

Enhancing both crop productivity and resource-use efficiency is essential for sustainable intensification, particularly in high-value vegetable systems. Conventional surface irrigation combined with one-time application of compound fertilizer often leads to poor synchronization between nutrient supply and crop demand, resulting in inefficient resource use and elevated environmental risks. This study investigated the effects of split N P K application via precision drip fertigation on soil conditions, crop performance, and water productivity in Brassica napus cultivated for edible shoots. Four fertilization treatments were compared: (T1) conventional surface irrigation with a single top-dressing of compound fertilizer, and three drip-fertigation regimes using organic water-soluble fertilizer-(T2) fertilizer applied in two equal splits, (T3) fertilizer applied in three equal splits, and (T4) fertilizer applied in four equal splits-synchronized with successive shoot-harvest stages. Results demonstrated that drip fertigation significantly improved subsoil moisture and reduced soil electrical conductivity. Notably, treatments T3 and T4 enhanced nitrate nitrogen availability, stem diameter, plant height, and biomass accumulation. Compared with T1, T3 and T4 increased shoot yield by 17.1 % and 9.31 %, irrigation water productivity (WP I ) by 17.1 % and 9.17 %, and partial factor productivity of N fertilizer (PFP N ) by 1.62 % and 7.63 %, respectively. Structural equation modeling identified stem diameter, dry weight, and inflorescence number as key yield drivers, while PFP N was affected by both morphological and physiological traits. A combined AHP-EWM evaluation framework identified T3 as the optimal fertilization regime. The fertigation strategy and evaluation framework developed here offer a practical and scalable pathway for enhancing water-nutrient efficiency in multi-cut vegetable systems, supporting sustainable intensification beyond the study region. • Split organic drip fertigation improved yield and PFP N in Brassica napus. • Harvest-synchronized fertigation enhanced regrowth and shoot yield. • Structural equation modeling identified stem diameter and biomass as key yield drivers.