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Abstract Regular large-scale application of fertilizers, pesticides, and mulching can lead to soil health degradation and increase negative environmental impacts, contributing significantly to greenhouse gas (GHG) emissions. Considering these factors by applying biochar and biofertilizer (rhizobium inoculants) in groundnut production, a novel experiment was conducted for increasing soil fertility, groundnut productivity, and soil carbon stock in Bangladesh's Charland agroecosystems. The two-year experiment involved seven treatments consisting of T 1 (control), T 2 (soil test based (STB) fertilizer dose following fertilizer recommendation guide (FRG) 2018), T 3 ((T 2 minus nitrogen fertilizer) + biofertilizer), T 4 (T 3 + biochar), T 5 (T 2 + biochar), T 6 (only biofertilizer), and T 7 (only biochar). The result showed that the T 4 treatment had the highest nodule counts (78.17 plant −1 ), nodule weights (122.97 mg plant −1 ), root weight (1.47 g plant −1 ) and nut yields (2.30 t ha −1 ), all of which were statistically identical compared to the other treatments. In addition, the T 3 treatment had the highest recorded shoot weight (35.47 g plant −1 ), whereas the control T 1 treatment had the lowest (16.50 g plant −1 ) shoot weight. Results showed that biochar-based rhizobium inoculants increased nodulation, root weight, shoot weight, nut yield and soil nutrient uptake in plant growth at all four stages (seedling, flowering, pod formation and harvesting). The result revealed that biochar-based rhizobium inoculants modulated the abundance of functional microbes through increased soil nitrification and reduced denitrification compared to the N-use treatments. Moreover, this interactive system significantly improved soil NO 3 − , leading to an increase in N uptake, thereby promoting plant growth and increasing nut yield. Considering all parameters, the soil amended biochar as a carrier of rhizobium inoculants had the highest soil organic carbon (SOC) stock (1.76 t ha −1 ), about 26% higher than other treatments, which saved a considerable amount of 6.6 kg CO 2 eq ha −1 GHG emissions and aided in promoting environmental sustainability towards climate-smart agriculture. Graphical Abstract
Shikha et al. (Fri,) studied this question.