Fertigation Effects on Nutrient Use Efficiency, Energy Productivity, and Economics of Coconut (<italic>Cocos nucifera</italic> L.) Cultivation in the Eastern Indo-Gangetic Plains of South Asia.

Drip fertigation has potential to reduce fertilizer dose in comparison to surface application in coconut (<italic>Cocos nucifera</italic> L.) by increasing its’ use efficiency in the Eastern Gangetic plains of South Asia. A long-term field experiment (2007–2013) was conducted on Inceptisol to evaluate 100% of the soil test-based recommended fertilizer dose (RDF; N:P2O5:K2O applied at 500:250:750 g palm−1 year−1) in soil with ring basin irrigation as conventional, 100%, 75%, 50%, 25%, and 0% of the RDF through drips. The fertigation level of 75% RDF resulted in 32%, 19%, 39%, and 16% higher copra yield, energy productivity, net return, and benefit-cost ratio, respectively, over conventional. Increasing trend of nutrient use efficiency was observed with decreasing dose of N, P and K. Use efficiencies decreased from 50.4 kg copra kg−1 N, 230.7 kg copra kg−1 P, and 40.5 kg copra kg −1 K (with 25% of the RDF through drip) to 6.1 kg copra kg−1 N, 27.8 kg copra kg−1 P, and 4.9 kg copra kg−1 K (with 100% RDF through ring basin irrigation). Fertigation with 75% RDF in drip had the highest copra yield (3.19 t ha−1), energy output (206082 MJ ha−1), energy productivity (187 g copra MJ−1), net returns (US $ 3073 ha−1), and benefit–cost ratio (2.36) compared to others. [ABSTRACT FROM AUTHOR]