Environmental Challenges (Aug 2022)
Organic material inputs are not essential for paddy soil carbon sequestration
Abstract
Carbon (C) emission as CO2 to the atmosphere at higher rates leads to global warming and climate change. Storing atmospheric C in the soil is achieved by soil C sequestration (SCS). In the phase of degradation of natural ecosystems, agroecosystems might play a crucial role in SCS. However, conventional methods like bulky organic material inputs in agricultural SCS will not be sufficient in the future scenarios of rapid CO2 emissions to the atmosphere. Also, preserving soil C stocks for prolonged periods has been one of the biggest challenges in agricultural SCS. In recent studies, the microbial interventions like biofilm biofertilizers (BFBF) have shown its potential in SCS. However, the effect of BFBF in maintaining soil C pools for prolonged periods has not been fully elucidated thus far. Therefore, for the first time, the present study evaluated the potential of BFBF in SCS and maintaining C pools in lowland paddy cultivation in three consecutive cropping seasons. Here, the BFBF practice was compared with the farmers’ current practice of chemical fertilizer (CF) alone application in 25 representative sites in four districts having ca. 0.5 Mha of paddy cultivation. In each site, two consecutive, uniformly managed paddy fields (each ca. 0.4 ha) with similar soil characteristics and grain yields were used to evaluate BFBF practice in comparison with farmers’ CF practice. The two consecutive field plots in each site were taken as a randomized block design. Four random rice hills and 12 random soil samples (0 to 20 cm depth) were collected at 50% flowering stage from each experimental paddy field to measure the root length and soil parameters, respectively. Soil organic and labile C contents were analyzed to calculate SCS. The results showed that gross C pool (GCP), a portion of which is emitted as CO2 during tillage, seems to play an important role in increasing the preserved soil C stock with time only in the BFBF practice, whereas it started to decline from the second season in the farmers’ CF practice. Moreover, the BFBF practice sequestered up to 15 t stable C ha–1 season–1 over the farmers’ CF practice showing the potential to mitigate global warming and to gain income through C trading. The increased SCS was due to increased rooting depth and microbial C assimilation in the root-zone soil. The BFBF practice requires only 2.5 l of BFBF ha−1, whereas conventional practices need bulky quantities of organic matter inputs to sequester a comparable amount of C. In addition, an increased grain yields up to ca. 25% was observed in the BFBF practice. Therefore, the BFBF practice can be considered as an eco-friendly and economically viable method to replace the farmers’ current practice of CF alone application.
