Fruit yield and water use efficiency of eggplant (Solanum melongema L.) as influenced by different quantities of nitrogen and water applied through drip and furrow irrigation

Elucidation of the effects of different quantities of nitrogen (N) and water applied through drip and furrow irrigation on fruit yield and water use efficiency (WUE) in eggplant is essential for formulating proper management practices for sustainable production. The present investigation was undertaken to evaluate the independent and interactive effects of four levels of N and different quantities of water applied through drip as well as furrow irrigation on eggplant fruit yield, agronomic efficiency of N and WUE. In the present field investigation, ridge planting with each furrow and alternate furrow irrigation were compared with drip irrigation at three levels of water: 100%, 75% and 50% of each furrow irrigation (designated as D1.0, D0.75 and D0.5). The four levels of N studied were 90, 120, 150 and 180 kg N ha−1 (designated as N90, N120, N150 and N180). The eggplant hybrid BH-1 was transplanted on August 5, 2004 at the spacing of 60 cm × 45 cm.The results revealed that fruit yield increased significantly with increasing N level up to N150 in each furrow as well as in alternate furrow irrigation although yield was significantly higher in each furrow irrigation. The highest yield under drip was obtained under D0.75 at N120, which was 23% higher and obtained with the saving of 25% water and 30 kg N ha−1 as compared with maximum yield obtained at each furrow irrigation at N150. The application of 50% water through drip can produce 4% higher yield as compared with each furrow irrigation at N150. The increase in fruit yield was the result of an increase in the number of fruits per plant (R2 = 0.80). In furrow irrigation, the WUE was 89.9 kg ha−1 mm−1 in alternate furrow as compared to 73.3 kg ha−1 mm−1 in each furrow irrigation at N150, where these treatments produced the highest quantities of fruit yield. The WUE at D0.75, which produced the highest fruit yield, was 109.9 kg ha−1 mm−1 at N120 but this increased to 119.9 kg ha−1 mm−1 in D0.5 at N150. The agronomic efficiency of N (AN) increased from 554 to 758 kg fruit per kg of N applied at N120 when water and N were applied through drip irrigation as compared to each furrow irrigation. These results suggest that determining different quantities of water through drip at different levels of N is essential to optimizing combinations to exploit the beneficial effects of drip irrigation and to obtain maximum yield accompanied by highest WUE and AEN.