Understanding the dynamics of carbon, water and water use efficiency fluxes at ecosystem scale in Maize crop

In a terrestrial ecosystem, water and carbon cycles are coupled with the linking eco-hydrological trait, water use efficiency (WUE). Understanding the dynamics of these fluxes in managed croplands is crucial in implementing sustainable irrigation strategies. However, knowledge of these fluxes, especially in semi-arid regions is poorly addressed due to lack of long-term flux measurements. This study is aimed at analysing the dynamics of carbon, water and WUE fluxes observed in a maize crop irrigated with both alternative furrow (AFI) and conventional furrow (CFI) schemes.  During the experiments, water-carbon fluxes and other related micro-metrological and environmental variables are continuously monitored using two eddy covariance (EC) flux towers installed in the maize fields. The results showed that: mean WUE is in the range 1.61 ± 0.23, and 1.21 ± 0.25 µmol m^-2 s^-1 CO₂ mm day^-1 H₂O for AFI and CFI respectively. A higher WUE in AFI by 1.33 times over CFI treatment is attributed to the differences in net ecosystem exchange (NEE). The correlation analysis showed that WUE is mainly affected by net ecosystem exchange (R² = 0.75 in AFI and 0.60 in CI) rather than ET fluxes. The environmental drivers of vapor pressure deficit of air and net solar radiation are mainly controlling WUE dynamics. Results concluded that the AFI irrigation treatments have more significant water-saving potential without compromising on carbon intake. These findings can set as a reference for the scientific development of typical water-saving practices of agriculture in India.