Effect of sequential tillage practices and N levels on energy relations and use-efficiencies of irrigation water and N in maize (Zea mays)–wheat (Triticum aestivum) cropping system

Field experiments were conducted during 2009–10 and 2010–11 at New Delhi to evaluate the effect of four sequential combinations of conventional tillage (CT) and zero tillage (ZT) practices in conjunction with N levels (0, 60, 120 and 180 kg N/ha) on energy relations and use-efficiencies of irrigation water (IWUE) and N (NUE) in maize (Zea mays L.)–wheat (Triticum aestivum (L.) emend. Fiori & Paol) cropping system. ZT practices saved on an average 20 and 15% input energy requirements over CT practices in maize and wheat, respectively. The maximum input energy requirement in maize–wheat cropping system was recorded under CT–CT tillage sequence, whereas the minimum was recorded with ZT–ZT sequential tillage system. The gross and net output energy productions by the maize-wheat cropping system were not influenced significantly due to different sequential tillage practices, however these were recorded maximum under CT–ZT sequential tillage system. Significantly maximum energy-use efficiency in maize–wheat cropping system was recorded with ZT–ZT sequence, which was 29.76, 19.44 and 11.49% higher than the CT–CT, CT–ZT and ZT–CT sequential tillage practices, respectively during the year 2010–11. ZT sown wheat based tillage sequences (CT–ZT and ZT–ZT) resulted 4–6% higher IWUE than CT sown wheat based tillage sequences (CT–CT and ZT–CT). The energy relations, IWUE and NUE parameters of both the crops differed significantly due to various N levels. The input and output energy and IWUE increased significantly with each successive increase in levels of N from 0 to 120 kg N/ha, while reverse trends were observed with energy-use efficiency and NUE, which were decreased significantly from 0 to 180 kg N/ha. Consequently ZT involving sequential tillage practices in conjunction with application of 120 kg N/ha may be adopted to enhance resource-use efficiency in maize–wheat cropping system.