Drip-Fed CO2 Acidifies the Rhizosphere to Liberate Nutrients and Boost Cotton Yield

Recycling industrial CO2 into agricultural systems offers a dual-purpose strategy for achieving carbon neutrality and enhancing sustainable crop production. Although elevated CO2 is known to influence plant growth, the directed delivery of industrially sourced CO2 via drip irrigation to modulate rhizosphere processes in arid soils remains underexplored. We conducted a two-year field experiment in a Xinjiang cotton field to evaluate the effects of five concentrations of industrial CO2 solution (0.00–0.16 kg·m−3) on soil properties, nutrient dynamics, and crop performance. The optimal CO2 treatment (0.08 kg·m−3) significantly reduced soil pH by up to 0.3 units and electrical conductivity by up to 27.9%, while enhancing the availability of ammonium-N (51.1%), available P (8.1%), and available K (32.65%). These improved soil conditions subsequently enhanced plant N, P, and K accumulation (56.2%, 41.9%, and 53.2%, respectively), total biomass (31.8%), and seed cotton yield (5.76–6.06%). Our findings demonstrate that CO2-enriched irrigation enhances the rhizosphere microenvironment and nutrient availability, providing a novel pathway for carbon recycling and high-efficiency cotton production in arid regions.