title: Soil carbon fractions under maize-wheat system: effect of tillage and nutrient management.
abstract: Soil organic carbon plays a major role in sustaining agroecosystems and maintaining environmental quality as it acts as a major source and sink of atmospheric carbon. The present study aims to assess the impact of agricultural management practices on soil organic carbon pools in a maize-wheat cropping system of Indo-Gangetic Plains, India. Soil samples from a split plot design with two tillage systems (bed planting and conventional tillage) and six nutrient treatments (T1 = control, T2 = 120 kg urea-N ha(-1), T3 = T2 (25 % N substituted by FYM), T4 = T2 (25 % N substituted by sewage sludge), T5 = T2 + crop residue, T6 = 100 % organic source (50 % FYM + 25 % biofertilizer + 25 % crop residue) were used for determining the organic carbon pools. Results show that there was a significant improvement in Walkley and Black carbon in soil under integrated and organic nutrient management treatments. KMnO4-oxidizable carbon content of soil varied from 0.63 to 1.50 g kg(-1) in soils and was found to be a better indicator for monitoring the impact of agricultural management practices on quality of soil organic carbon than microbial biomass carbon. Tillage and its interaction were found to significantly influence only those soil organic carbon fractions closely associated with aggregate stability viz, labile polysaccharides and glomalin. The highest amount of C4-derived carbon was found to be in plots receiving recommended doses of N as urea (29 %) followed by control plots (25 %). The carbon management index ranged between 82 to 195 and was better in integrated nutrient sources than ones receiving recommended doses of nutrients through mineral fertilizers alone.
authors.affiliation: Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, 110012, India. sandeep.kfri@gmail.com.|Department of Soil Science, Kerala Forest Research Institute, Peechi, Thrissur, Kerala, 680653, India. sandeep.kfri@gmail.com.
authors.forename: S
authors.initials: S
authors.lastname: Sandeep
authors.affiliation: Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, 110012, India. manjaiah@iari.res.in.
authors.forename: K M
authors.initials: KM
authors.lastname: Manjaiah
authors.affiliation: Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, 110012, India. sharmistha.ars@gmail.com.|ICAR - Indian Institute of Soil & Water Conservation, Research Centre, Chandigarh, 160019, India. sharmistha.ars@gmail.com.
authors.forename: Sharmistha
authors.initials: S
authors.lastname: Pal
authors.affiliation: Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, 110012, India. aks_wtc@yahoo.com.|Rajmata Vijayaraje Scindia Krishi Vishwavidyalaya, Gwalior, 474002, Madhya Pradesh, India. aks_wtc@yahoo.com.
authors.forename: A K
authors.initials: AK
authors.lastname: Singh
mesh_terms: D000383:Agriculture / Q000379:methods*; D018533:Biomass; D002244:Carbon / Q000032:analysis*; D018556:Crops, Agricultural / Q000254:growth & development; D004777:Environment; D004784:Environmental Monitoring; D005308:Fertilizers / Q000032:analysis; D007194:India; D012987:Soil / Q000737:chemistry*; D014908:Triticum; D003313:Zea mays
chemical_list: D005308:Fertilizers; D012987:Soil; D002244:Carbon
keywords: Carbon management index; KMnO4-oxidizable carbon; Maize–wheat cropping system; Microbial biomass carbon; Walkley and Black carbon