Soil organic carbon (SOC) pools are important for maintaining soil productivity and reducing the net CO2 loading of the atmosphere. An 18‐year old long‐term field experiment involving pearl millet‐cluster bean‐castor sequence was conducted on an Entisol in western India to examine the effects of chemical fertilizers and manuring on carbon pools in relation to crop productivity and C sequestration. The data showed that even the addition of 33.5 Mg ha−1 C inputs through crop residues as well as farm yard manure could not compensate the SOC depletion by oxidation and resulted in the net loss of 4.4 Mg C ha−1 in 18 years. The loss of SOC stock in the control was 12 Mg C ha−1. Conjunctive use of chemical fertilizers along with farm yard manure produced higher agronomic yields and reduced the rate of SOC depletion. The higher average seed yields of pearl millet (809 kg ha−1), cluster bean (576), and castor (827) over six cropping seasons were obtained through integrated use of fertilizers and manure. For every Mg increase in profile SOC stock, there was an overall increase of 0.46 Mg of crop yield, comprising increase in individual yield of pearl millet (0.17 Mg ha−1 y−1 Mg−1 SOC), cluster bean (0.14) and castor (0.15). The magnitude of SOC build up was proportional to the C inputs. Carbon pools were significantly correlated with SOC, which increased with application of organic amendments. Threshold C input of 3.3 Mg C ha−1 y−1 was needed to maintain the SOC stock even at the low antecedent level. Copyright © 2011 John Wiley & Sons, Ltd.

Soil quality is a concept that integrates soil biological, chemical, and physical factors into a framework for soil resource evaluation (Karlen et al., 1997). Larson and Pierce (1991) define soil quality as the capacity of a soil to function within the ecosystem boundaries and to interact positively with surrounding ecosystems. Conversion of forest and grasslands into agricultural land is one of the main concerns worldwide in the context of environmental degradation and global climate change (Wali et al., 1999). Conversion of natural land resources to crop production as the largest source of anthropogenic carbon emissions after fossil fuel burning, has resulted in the release of about 200 Pg C over the past 250 years, globally (Scholes and Noble, 2001; Fitzsimmons et al., 2004). It is also very well known that cultivation of the natural land resources brings about the loss of OM and this directly affects the soil chemical, physical, and biological properties resulting in loss of

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Beneficial aspects of endophytic microorganisms have motivated researchers to explore plant endophytic world. The present study was aimed to isolate and characterize the seed-borne endophytic bacteria from diverse maize genotypes. Eighty maize seed endophytic bacteria (MSEB), isolated from 30 maize genotypes, were characterized using polyphasic approach. The dendrograms and phylogenetic tree generated on the basis of ARDRA analysis and metabolic profiling of endophytic bacteria revealed genotypic and biochemical diversity among MSEB. The 16S rDNA sequence analysis revealed Bacillus as the most dominant encountered genus affiliated with Phylum Firmicutes. Few isolates belonged to genus Staphylococcus, whereas one isolate was identified as Corynebacterium sp. under Phylum Actinobacteria. Majority of the MSEB isolates exhibited antagonism against phytopathogenic fungi, production of ammonia, and secretion of lytic enzymes; some isolates also exhibited indole acetic acid production, the traits of which can be helpful in endophytic establishment and advantageous to the host plant. Besides, many MSEB exhibited tolerance to salinity (10%), osmotic stress (40% PEG6000), and temperature (60 °C), indicating their possible application under stress conditions. Endophytic nature of the selected MSEB isolates was confirmed by tracking their presence in shoots, leaves, and roots of the host seedlings with the help of biochemical marker (rifampicin resistance). Thus, the MSEB identified in the present study can be explored as potential bioinputs for improving plant growth and productivity under stressed conditions, besides helping in understanding the plant-endophyte interactions.

Enricbment of soil organic carbon (SOC) stocks through sequestration of atmospheric CO2 in agricultural soils is important because of its impacts on soil quality, agronomic production, and adaptation to and mitigation of climate change. In a 21-yr field experiment conducted under subbumid tropical conditions in India, the impacts of crop residue C inputs were assessed for the rice (Oryza sativa L.)-lentil (Lens esculenta Moench) cropping sequence. These impacts were evaluated in an experiment involving mineral fertilizers and manuring treatments on crop yield sustainability with reference to critical biomass requirements for maintenance of SOC in an Inceptisol. Application of farmyard manure (FYM) without and with mineral fertilizers increased C input and SOC concentration and stock. In comparison with the control, the 1007<. organic (FYM) treatment had significantly bigher profile SOC (27.5 Mg ha"'), and more C build up (55,0%) and C sequestration (6.6 Mg C ba"') to 1-m depth vis-à-vis the antecedent values in 1986. These parameters were also higher in 100% FYM treatment at a rate providing equivalent amount of tbe recommended dose of N followed by conjunctive use of FYM and mineral fertilizers. The SOC stock and rate of sequestration were positively correlated witb cumulative C input, and with sustainable yield index (SYI) of upland rice and lentil. Higher grain yield (1.95 and 1.04 Mg ha"' of rice and lentil, respectively) was obtained with tbe application of 50% organic (FYM)-i-50% recommended dose of fertilizer (RDF). In comparison, higher SOC sequestration rate was measured witb tbe application of 100% organic (FYM). For every Mg increase in SOC stock in the root zone there was 0.16 and 0.18 Mg ba"'yr"' yield increase of rice and lentil, respectively. For maintaining a stable SOC level (zero change due to cropping), a minimum quantity of 2.47 Mg C ba"' yr"' is required for this soil, climate, cropping system, and fertilization treatments. To achieve this quantity of C, 7.1 Mg of biomass is required to be produced every year vs. average rice and lentil yields of 1.6 and 0.7 Mg ba"', respectively. The sole application of mineral fertilizers at 50 or 100% of the RDF did not maintain the SOC stock. Thus, application of FYM (or other organics) in conjunction with mineral fertilizers is essential to maintaining and enhancing the SOC stock in the rice-based cropping systems.Abbreviations: BD, bulk density; FYM, farmyard manure; INM, integrated nutrient management;NUE, nitrogen use efficiency; RDF, recommended dose of fertilizer; SOC, soil organic carbon; SOM, soil organic matter; SYI, sustainable yield index. R esearch information on rate of enrichment of SOC stocks through .sequestration of atmospheric CO2 in agricultural soils is important because of its impacts on adaptation to and mitigation of climate change, crop productivity, and sustainability. Soil organic matter (SOM) constitutes a signifi-

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