Vol. 11, Issue 4 (2022)

Author(s):
Himanshu Tiwari, RK Naresh, Dhiru Kumar Tiwari, Manisha, Yogesh Kumar, Ankit Tiwari, Shubhendu Singh and Ravindra Sachan

Abstract:
Poor soil fertility and soil degradation induced by persistent conventional farming with repeated tillage and removal or in situ burning of crop residue are major limitations to food security and environmental sustainability. However, degraded agricultural lands with depleted soil organic carbon (SOC) stocks are capable of soil carbon restoration through improved management practices like aggregation, humification and deep placement of C that can increase SOC sequestration. The fate of SOC in cropland soils plays a significant role in both sustainable agricultural production and climate change mitigation. Tillage systems can influence C sequestration by changing aggregate formation and C distribution within the aggregate. Average SOC concentration of the control treatment was 0.54%, which increased to 0.65% in the RDF treatment and 0.82% in the RDF+FYM treatment and increased enzyme activities, which potentially influence soil nutrients dynamics under field condition. Compared to F₁ control treatment the RDF+FYM treatment sequestered 0.28 Mg C ha^-1yr^-1 whereas the NPK treatment sequestered 0.13 Mg C ha^-1yr^-1. As tillage intensity increased there was a redistribution of SOC in the profile, but it occurred only between ZT and PRB since under CT, SOC stock decreased even below the plow layer. Increased SOC stock in the surface 50 kg m^-2 under ZT and PRB was compensated by greater SOC stocks in the 50-200 and 200-400 kg m^-2 interval under residue retained, but SOC stocks under CT were consistently lower in the surface 400 kg m^-2. Soil carbon (C) pools and biological indicator plays an important role in maintaining soil quality. Vermicompost + NPK treatment recorded the highest oxidizable organic carbon (0.69%), dissolved organic carbon (0.007%) and microbial biomass carbon (0.01%), followed by FYM + NPK, GL + NPK and RS + NPK as compared to control. Rice straw + NPK sequestered the highest amount of carbon dioxide (CO₂) as the total organic carbon (91.10 t ha^-1) and passive pool of carbon (85.64 t ha^-1), whereas VC + NPK resulted in the highest amount of CO₂ (10.24 t ha^-1) being sequestered as the active pool of carbon, followed by FYM + NPK (8.33 t ha^-1) and GL + NPK (7.22 t ha^-1). The soil microbial biomass carbon significantly varied across the treatments from 129.4 to 412.1 µg g⁻¹ which comprises 2.4 to 4.4% of the SOC. The highest bacterial count (8.95 log cfu g⁻¹ soil) was recorded in RDF + Azolla treatment, whereas fungal count was the maximum (7.47 log cfu g⁻¹ soil) in RDF + FYM treatment. All the enzymatic activities responded significantly to the INM practices, but the trend of response was different for different enzymes. The highest dehydrogenase (223.6 µg TTF g⁻¹ soil 24 h⁻¹) and urease (4.1 μg NH₄-N g⁻¹ soil 2 h⁻¹) activities were recorded in RDF + Azolla, while phosphomonoeaterase (337.4 μg p-nitrophenol g⁻¹ soil h⁻¹) and fluorescein diacetate hydrolysis (10.0 μg fluorescein g⁻¹ soil h⁻¹) activities were found to be the maximum in RDF + FYM. However, Total organic carbon input of soil was increased by 10.2 - 23.3 kg Cha^-1yr^-1, and increment rate in the appended manure treatments were much higher than those in the control and inorganic fertilizer treatments. Soil organic carbon retention in the topsoil (0 - 20 cm) decreased by 0.11 - 0.14 tha^-1yr^-1 in the control, N and NP treatments; nevertheless, soil organic carbon sequestration rates varied from 0.03 to 0.20 tha^-1yr^-1 in the NPK and appended organic manure treatments. Adding carbon materials to soil is thereby not directly sequestration, as interaction of appropriately designed materials with the soil Microbiome can result in both: metabolization and thereby non-sustainable use of the added carbon, or-more favourably-a biological amplification of human efforts and sequestration of extra CO₂ by microbial growth.