Optimization of elevated CO2 levels and nutrient management for lowland rice ecosystem

Experiments were conducted to assess the optimum CO2 levels and nutrient management strategy for enhancing the rice yield and soil fertility status with rice (var.CO. 50) as test crop in open top chambers (OTC). The treatments comprised of three levels of CO2 enrichment viz., Atmospheric CO2 (C0): 370 ppm (Control); OTC I (C1): 550 ppm and OTC II (C2): 750 ppm. Both the OTC chambers were connected to a control monitoring system and the each chamber has a regulator to adjust CO2 flow. Rice crop was fertilized with four varying nutrient management techniques viz., inorganic (150:50:50 kg N, P, K ha−1 +25 kg ZnSO4 ha−1), organic (1/3rd FYM+ 1/3rd Vermicompost + 1/3rd Neem cake on N equivalent basis), IPNS (Integrated Plant Nutrient System) (150:50:50 kg N, P, K ha−1 +25 kg ZnSO4 ha−1 +FYM @ 12.5 t ha−1 + Azospirillum @ 2 kg ha−1) and untreated control. Maximum grain and straw yields were recorded due to the application of Integrated Plant Nutrient System (150:50:50 kg N, P, K ha−1 +25 kg ZnSO4 ha−1 +FYM @ 12.5 t ha−1 + Azospirillum @ 2 kg ha−1) in the CO2 concentration of 750 ppm. Highest acid phosphatase activity was registered at the CO2 concentration of 750 ppm followed by 550 ppm and 370 ppm. Acid phosphatase activity was the highest due to the application of organics (1/3rd FYM+ 1/3rd Vermicompost + 1/3rd Neem cake on N equivalent basis) followed by the application of 150:50:50 kg N, P, K ha−1 +25 kg ZnSO4 ha−1 +FYM @ 12.5 t ha−1 + Azospirillum @ 2 kg ha−1. With increase in CO2 concentration an increase in CO2 emission and microbial biomass were observed.