ASSESSMENT OF CARBON FOOTPRINT IN RICE-RICE CROPPING SYSTEM AS AFFECTED BY FERTILIZER MANAGEMENT
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Date
2019-07
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AAU, Jorhat
Abstract
The present study aimed at assessing the carbon footprint in rice-rice cropping system as affected by various fertilizer management combinations and source of nitrogen was carried out in the ICR Farm, AAU (26°71'N, 94°18' E) 91.0 m above MSL during the years 2016-17 and 2017-18. The initial pH, organic carbon, available N, P2O5 and K2O of the experimental plot were 5.84, 0.61%, 132.561 kg ha-1, 214.48 kg ha-1 and 33.734 kg ha-1, respectively.
There were no significant differences in soil pH amongst the variety while significant differences were observed within various fertilizer combinations and source of N. Soil organic carbon values ranged between 0.62 to 0.85% and significant difference was observed amongst the fertilizer treatments and source of N. The various fertilizer combinations in case of available nitrogen also showed a similar trend with the highest mean value of 169.84 kg Nha-1 in the treatment with full recommended dose of fertilizer (RDF). Available P2O5 in the system also followed a similar trend (36.07 kg ha-1) while available K2O significantly varied within the varieties and fertilizer combinations with higher values in Mahsuri-Banglami system (49.94 kg K2O ha-1).
Significant differences in methane emissions were observed amongst the varieties and also in between the fertilizer combination treatments.The methane emission was 388.33 mg m-2hr-1 in Ranjit-Lachit system and 285.61 mgm-2hr-1 in the Mahsuri-Banglami cropping system. High methane emission was observed in RDF followed by 50% RDF+Vermicompost and INM. During the entire crop growing season, the largest variation in methane emission was observed in the early growth period. Methane emission indicated two distinct peaks during the entire crop growth period, irrespective of the treatments. Peaks of nitrous oxide emissions were obtained after topdressing of nitrogenous fertilizers. Significant variations were also observed in between the fertilizer combination treatments may be due to varying organic carbon in the various treatments. Ranjit-Lachit system recorded higher mean cumulative N2O emissions (10.72 gm-2) than Mahsuri-Banglami system (4.92 gm-2). The RDF treatments recorded highest mean cumulative N2O emissions amongst the fertilizer combinations. Temporal pattern of flux irrespective of treatments showed a trend of gradual increase with the growth of the crop, thereafter a slow decline in fluxes. The highest mean cumulative CO2 emissions (2953.43 mg m-2) was recorded in the Ranjit-Lachit system and within the fertilizer combinations, the highest mean value of 3125.20 mg m-2 was recorded under RDF treatment. Mapping of the three different tiers of carbon footprint showed that the tier-1 was the dominant contributor of carbon footprint.
The Total System Spatial Carbon Footprint (SCF) under different treatments recorded higher values in case of INM treatments involving 50%NP + Full K + 5t/ha enriched compost and vermicompost treatments in both the cropping systems. Within the INM treatments, higher SCF of 62.00 t CE ha-1 was obtained in Ranjit-Lachit system while in case of Mahsuri-Banglami system, the highest SCF was obtained in INM treatment with NCU and UCU (48.91 t CE ha-1). Yield scaled carbon footprint (YCF) indicated highest value of 13.23 kg CE kg-1 grain in case of Mahsuri-Banglami system while 50% RDF supplemented with 5 t ha-1vermicompost and uncoated urea recorded the highest YCF with 15.96 kg CE kg-1 of grain in Ranjit-Lachit cropping system. Considering the yield compensation and sustainability of the soil resources, the INM with slow release N source proved to be the better in rice-rice cropping system.