Optimizing water and nutrient delivery through precision drip fertigation boosts fennel productivity and resource-use efficiency in arid agroecosystems

Fennel ( Foeniculum vulgare Mill.) is a vital seed spice crop cultivated in arid and semi-arid regions of India, where water scarcity and nutrient inefficiency constrain productivity. To address these challenges, a comprehensive three-year field study (2016-17, 2017-18 and 2018-19) was conducted to assess the effects of drip fertigation under varying irrigation regimes and fertilizer levels on fennel growth, yield, Water-Use Efficiency (WUE), and economic returns. The experiment comprised ten treatments, including surface irrigation (T 1 /control) and nine drip fertigation combinations structured across three IW/CPE levels (0.4, 0.6, and 0.8) and three fertilizer levels (60, 80 and 100% of RDF i.e. 90:40:30 N: P:K). Drip fertigation at 0.8 IW/CPE with 100% RDF (T 10 ) significantly enhanced plant height (195.3 cm), primary and secondary branches, umbels per plant (71.4), umbellets per umbel (71.34), seed yield (2,705 kg ha − 1 ), essential oil content (1.63%), and net returns (₹1,78,628 ha − 1 ), with a benefit-cost ratio of 2.84, along with significantly higher test weight reflecting improved seed filling and quality under optimized drip fertigation. Although the highest WUE (7.24 kg/ha-mm) was recorded under T 4 (0.4 IW/CPE with 100% RDF), T 10 offered the best balance between seed productivity and economic returns. Correlation and regression analyses revealed strong positive associations between growth parameters and seed yield, validating their role as reliable indicators for agronomic optimization. Multivariate analyses further showed that T 10 was associated with consistently high productivity and economic performance across the three seasons. Overall, the findings underscore the potential of drip fertigation particularly at 0.8 IW/CPE with full nutrient supply as a sustainable, water-efficient, and economically viable strategy for enhancing fennel cultivation in water-limited environments.