Background:&nbsp;Rising atmospheric CO2&nbsp;and temperature due to climate change pose significant threats to agricultural productivity, particularly in semi-arid tropics. These changes can alter weed distribution, population dynamics and crop-weed interactions. Assessing groundnut&rsquo;s adaptability to changing climates, weed competition and herbicide efficacy is crucial for developing resilient cultivars and effective herbicide management systems to mitigate yield and quality losses, thereby enhancing global food security. 
 
Methods:&nbsp;A two-year (2022-23 and 2023-24) experiment was conducted in a Carbon Dioxide and Temperature Gradient Chamber (CTGC) at the Central Research Institute for Dryland Agriculture, Hyderabad. The study evaluated groundnut under four climate variables: ambient CO2&nbsp; + ambient temperature (aCO2&nbsp;+ aT) (396-405ppm), elevated CO2&nbsp;(eCO2, 550 &plusmn; 50 ppm), elevated temperature (eT, +2&deg;C) and combined eCO2&nbsp;+ eT (550 &plusmn; 50 ppm and +2&deg;C) , three crop-weed combinations (groundnut + C3&nbsp;weeds, groundnut + C4&nbsp;weeds, groundnut + C3&nbsp;+ C4&nbsp;weeds) and four herbicide rates (0X, 1X, 1.5X, 2X) using a completely randomized design. Growth parameters, soil rhizobium population and nodulation were assessed at 60 days after sowing (DAS). 
 
Result: Pooled data revealed that eCO2&nbsp;significantly enhanced groundnut growth and nodulation, with increases in plant height (25%), leaf area (26%), chlorophyll content (12%), Rhizobium population (22%), nodulation (58%) and dry matter production (22%) compared to ambient conditions. Combination of elevated CO2&nbsp;and temperature also showed positive effects, though less pronounced, while et alone reduced all parameters. Herbicide application at various rates showed suppressive effect on Rhizobium population, nodulation and chlorophyll content compared to no application. However, plant height, leaf area and dry matter production were significantly higher at 1.5 X rate over no application under eCO2 conditions in contrast to 1.0X rate under aCO2&nbsp;+ aT, eCO2&nbsp;+ eT and eT conditions. Groundnut exhibited better competitiveness against C4&nbsp;weeds compared to C3&nbsp;weeds or their combination. The findings revealed that groundnut growth and nodulation were significantly enhanced in treatments eCO2&nbsp;and eCO2&nbsp;+ eT but reduced under eT. Herbicide efficacy declined under eCO2, suggesting the need for higher application rate under future climate scenarios. These findings highlight the importance of adaptive strategies to sustain groundnut productivity under climate change scenario.

Impact of elevated CO2 and Temperature on Nodulation and Crop Weed Competition in Groundnut (Arachis hypogaea L.)

Impact of elevated CO₂ and Temperature on Nodulation and Crop Weed Competition in Groundnut (Arachis hypogaea L.)