title: Monitoring temperature sensitivity of soil organic carbon decomposition under maize-wheat cropping systems in semi-arid India.
abstract: Long-term storage of soil organic carbon (SOC) is essential for sustainability of agricultural ecosystems and maintaining overall environment quality as soils contain a significant part of global carbon stocks. In this study, we attempted to explain the carbon mineralization and temperature sensitivity of SOC in maize-wheat systems, a common cropping system in the semi-arid regions of India. Soil samples(0-0.15 m) from long-term experimental plots laid in split plot design with two tillage systems (conventional tillage and bed planting) and six nutrient management treatments (T 1 = control, T 2 = 120 kg urea-N/ha, T 3 = T2 (25 % N substituted by farmyard manure (FYM)), T 4 = T 2 (25 % N substituted by sewage sludge), T 5 = T 2 + crop residue, T 6 = 100 % recommended doses of N through organic source - 50 % FYM + 25 % biofertilizer + 25 % crop residue) were incubated at different temperatures (25, 30, 35, and 40 °C) to determine the thermal sensitivity parameters associated with carbon mineralization. Earlier reports suggest a selective preservation of C3-derived carbon fractions over C4 in the SOC pool, and this is the first instance where δ (13)C signatures (C4-derived carbon) were used as a qualitative measure to assess thermal sensitivity of SOC pools in the maize-wheat crop rotation systems of semi-arid India. Among the nutrient management treatments, mineral fertilizers were found to add more C4-derived carbon to the SOC pool in both the tillage systems but shows less promise in SOC stability as indicated by their lower activation energies (Ea) (14.25 kJ mol(-1)). Conventional tillage was found to mineralize 18.80 % (T 1-control at 25 °C) to 29.93 % carbon (T 3-mineral fertilizer + FYM at 40 °C) during the 150 days of incubation which was significantly higher than bed planting system (14.90 % in T 1-control at 25 °C and 21.99 % in T 6-100% organic sources at 40 °C). Organic manures, especially FYM (19.11 kJ mol(-1)) and 100 % organics (19.33 kJ mol(-1)) were more effective in enhancing the Ea of SOC than plots with mineral fertilizers alone (14.25 kJ mol(-1)), but had relatively higher Q 10 values thereby corroborating the thermal sensitivity hypothesis of recalcitrant organic compounds in soil. Michaelis-Menten derivatives along with thermal sensitivity indicators such as Ea and Q 10 were found to be efficient parameters for explaining carbon mineralization and CO2 efflux from soils.
authors.affiliation: Department of Soil Science, Kerala Forest Research Institute, Peechi, Thrissur, Kerala, 680653, India. sandeepagri@gmail.com.
authors.forename: S
authors.initials: S
authors.lastname: Sandeep
authors.affiliation: Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, Indian Council of Agricultural Research, New Delhi, 110012, India.
authors.forename: K M
authors.initials: KM
authors.lastname: Manjaiah
authors.affiliation: Department of Soil Science and Agricultural Chemistry, College of Horticulture, Kerala Agricultural University, Vellanikkara, Thrissur, Kerala, 680656, India.
authors.forename: M R
authors.initials: MR
authors.lastname: Mayadevi
authors.affiliation: Rajmata Vijayaraje Scindia Krishi Vishwavidyalaya, Gwalior, Madhya Pradesh, 474002, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Singh
mesh_terms: D000383:Agriculture; D057486:Carbon Cycle; D018556:Crops, Agricultural / Q000254:growth & development; D003889:Desert Climate; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D005308:Fertilizers; D006812:Humic Substances / Q000032:analysis; D007194:India; D008372:Manure; D012987:Soil / Q000737:chemistry*; D013696:Temperature; D014908:Triticum / Q000254:growth & development*; D003313:Zea mays / Q000254:growth & development*
chemical_list: D005308:Fertilizers; D006812:Humic Substances; D008372:Manure; D012987:Soil
keywords: Activation energy; C4-derived carbon; CO2 efflux; Maize-wheat; Michaelis–Menten kinetics; Q 10