Assessment of gains in productivity and water-energy-carbon nexus with tillage, trash retention and fertigation practices in drip irrigated sugarcane

Sugarcane is a major contributor to bioenergy production in India and its share is expected to rise further. However, the productivity of sugarcane is not only low, but it is also water-energy-carbon extensive. To work out energy and emission-centric strategies, effects of conservation agriculture-based tillage, surface trash retention, and nutrient management were monitored in drip irrigated sugarcane experiment (2016–22). Six treatments imposed on the plant crop consisted of: three tillage levels viz., CT (conventional tillage i.e. sub-soiling plus cultivating twice followed by rotovator), RT1 (reduced tillage cultivating twice) and RT2 (reduced tillage single cultivation) before preparing ridges for planting in main-plots and two trash management practices viz., M (trash mulching) and NM (non-mulching) in subplots. RT2 and RT1 rather increased plant crop productivity by 13.3 % and 8.2 % over CT, while the increase with M was 5.3, 7.9, and 10.1 %, respectively under CT, RT1 and RT2. The sub-sub plots for the following four ratoon crops included three modes of nutrient management as varied using both a multi-functional (stubble shaving, off-barring, root pruning and band placement of fertilisers) ratoon drill (MRD) for basal dose and fertigation with drippers during crop growth. These consisted of: N1 (25 % recommended fertilisers, RDF as basal and rest through fertigation); N2 (50 % with MRD and 50 % with fertigation) and N3 (75 % with MRD and 25 % with fertigation). RT2+ M + N2 enhanced tillers, cane weight, size matrices, juice quality and produced 45.4 % higher cane yield of ratoon crops compared with CT + NM + N1 (farmers practice). This reduced the yield gap from 38 to 8 % between plant and ratoon crops via its superior water productivity (16.4 kg m−3), partial factor productivity (518.1 kg N kg−1), and reduced water footprint (54.0 l kg−1). The energy consumption during ratoon crops (40.4–50.5 GJ ha−1) was considerably lesser than the plant crop (74.6–87.7 GJ ha−1). Similarly, GHG emissions monitored were 6522–7487 and 9001–10421 kg CO2-eq ha−1 during ratoon and plant crop, respectively. Reduced tillage in ratoons improved energy use efficiency (33.7–56.3 %), net energy (26.3–46.7 %) and reduced GHGs emissions by 3.6–12.9 % compared to CT + NM + N1. This enhanced carbon sequestration by 65.5–73.1 % and reduced carbon footprint by 72–88 %. Thus, integrating reduced tillage, trash retention and appropriate fertigation practices has a potential to improve sugarcane productivity vis-a-vis profitability, and sustain soil and environmental quality in sugarcane production systems, as prevalent in water scarcities regions.