Influence of Open and Polyhouse Conditions on Soil Carbon Dioxide Emission from Amaranthus Plots with Different Nutrient Management Practices under Changing Climate Scenario

A field study was conducted using Amaranthus to assess the impact of increased temperature in polyhouse with three different treatments, viz. 100% organic, 100% inorganic and 50% organic + 50% inorganic nutrition on growth, yield and carbon dioxide (CO₂) evolution compared to that of open natural condition. Among the different treatments applied, 100% application of organic manure resulted in maximum CO₂ emission in both open (538 mg) and polyhouse conditions (551 mg). The lowest value of CO₂ evolution (266 mg) was observed with 100% application of inorganic fertilizers under polyhouse conditions. In all the three treatments, CO₂ evolution almost reached a plateau and stabilized during the last two observations. At the last interval, CO₂ evolution ranged from 4.00 to 6.80 mg in all the treatments. However, cumulative CO₂ evolution showed that the emission was higher under open natural conditions (434 mg) compared to the polyhouse conditions (398 mg) at elevated temperature. This indicated that the microbial respiration was higher under natural conditions. Ambient air temperature and soil temperature were higher under polyhouse condition than open natural condition. However, soil moisture was higher under open condition than polyhouse condition for most observations. It could be observed from the experiment that Amaranthus production declined with increase in temperature, and maximum yield was obtained with 100% application of organic manure under open condition. Under elevated temperature condition in polyhouse, 50% application of inorganic fertilizer + 50% application of organic manure (T₃) registered the maximum crop production. This suggests that sufficient mitigation strategies need to be adopted for sustaining crop production under changing climate scenario.