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Due to increased contribution from agriculture sector to total greenhouse gas emissions, there is need to study the ability of no-tilled diverse cropping systems including crop sequences and bio-covers to mitigate C equivalent emissions. Thus, C-footprint was calculated for a long-term experiment at the University of Tennessee's Research and Education Center in Milan with six-crop sequences: continuous cotton (Gossypium hirsutum L.), cotton-corn (Zea mays L.), continuous corn, corn-soybean (Glycine max L.), continuous soybean, and soybean-cotton interacted with four bio-covers: poultry litter, hairy vetch (Vicia villosa), winter wheat (Triticum aestivum), and fallow control with three replicates in a strip-plot design. During the experiment duration (2002-2017), field inputs (fertilizers, pesticides, and machinery used for planting, chemical applications, and harvesting) and outputs (crop yield, aboveground, and belowground residue) were assessed for each crop sequence/bio-cover combination to calculate total C equivalence of inputs and outputs, net C gain, C footprint per kg yield, sustainability index, and nitrous oxide emissions. For continuous corn, C-based input emissions were significantly higher by 0.28-0.62 Mg CO 2 eq. ha -1 yr -1 than all other sequences, however, a greater net C gain (5.4 Mg C eq. ha -1 yr -1 ) was also observed due to increased crop yield, aboveground and belowground residues. Poultry litter application resulted in lower C-footprint (1.59-2.09 kg CO 2 eq. kg -1 yield) than hairy vetch, wheat, and fallow under all crop sequences. Hairy vetch also lowered C-footprint per kg yield (∼2-14%) when compared with wheat under continuous systems of corn, soybean, and cotton, and cotton-corn rotation. Poultry litter application increased sustainability index (23-45) of all cropping sequences compared with other bio-covers. Hairy vetch improved sustainability index of corn including cropping sequences as compared with wheat and fallow. Inclusion of soybean and cotton with corn significantly decreased nitrous oxide emissions by 20-25%. The major factor contributing towards C-based input emissions was N fertilizer with 68% contribution to total emissions on average. It is concluded that application of poultry litter can reduce per yield C-footprint and enhance production system sustainability compared with hairy vetch, wheat, and fallow for monocultures or rotations of corn, soybean, cotton. Additionally, hairy vetch can outperform wheat in reducing the per yield C-footprint for continuous corn/soybean/cotton, and cotton-corn rotation. Especially for corn production systems, hairy vetch can enhance sustainability index compared with wheat and fallow. In order to increase per hectare net C gain, reduce per yield C-footprint and enhance sustainability index simultaneously, integration of continuous corn or corn-soybean/cotton rotation with bio-cover poultry litter or hairy vetch may perform better than the monocultures of soybean or cotton integrated with bio-cover wheat or fallow control in the Mid-south USA., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The agriculture sector, which accounts for about 52% of the total workforce despite a steady decline of its share in the gross domestic product (GDP), is still the largest economic sector that plays a significant role in the overall socio-economic development of India. Sustainability of agricultural production systems depends on their carbon (C) footprint and the C output-input ratio. Thus, the present study was conducted with the objectives to: (i) assess C emissions in relation to predominant agricultural systems in India; (ii) evaluate C-use efficiency of production systems; and (iii) determine the relative sustainability of agronomic production systems as determined by their C footprints. The data collated on C-based input into the soil for predominant agricultural and horticultural crops included the amounts of fertilizers (N, P, K), herbicides, and pesticides used for crops annually, cropland area, total production of each crop, water-management practices, energy used for different operations, and total number of livestock. These data were used to compute C equivalent (Ce) per hectare of input and output, and the relative sustainability indices as a measure of the C-production efficiency. Beginning with low C-based input of 69.7 Tg Ce/yr (1 Tg = teragram = 1012g = 1 million ton) in 1960-61, input of fertilizers, pesticides, farm power, feed, fodder, and electricity increased to 281.2 Tg Ce/yr by 2008-09. The output in agriculture increased from 578.6 Tg Ce/yr in 1960-61 to 1239.1 Tg Ce/yr in 2008-09. The C-sustainability index was high in 1960, and was indicative of the minimum usage of inputs prior to the onset of the Green Revolution. Thereafter, the C-sustainability index decreased during 1970s and 1980s because of increased C-based inputs. There existed a linear relationship between C input and C output, indicating that an increase of 1 Tg Ce/yr of C input resulted in a corresponding increase in C output of ∼21 Tg Ce/yr. Total food grain production in India increased from 89 million ton in 1960-61 to 262 million ton in 2008-09. [ABSTRACT FROM AUTHOR]