Table 1. Definition of variables.

Variables	Definitions
Agricultural methane(CO4)	Agricultural methane emissions are emissions from animals, animal waste, rice production, and agricultural waste burning. It is negatively related to input productivity [10, 11].
CO2 emission	Carbon dioxide emissions are those stemming from the burning of fossil fuels and the manufacture of cement. It has negatively affected input returns [78– 81].
GDP per capita income	GDP is the sum of the gross value added by all resident producers in the economy plus any product taxes and minus any subsidies not included in the value of the products. It is directly related to input return [82].
Labor productivity $\left(\frac{y_{it}}{l_{ait}}\right)$	It is the percentage of total cereal yield, measured as kilograms per hectare of harvested land, per total labor engaged in agriculture. It is positively associated with the technical efficiency of crop yields [57, 67, 83, 84].
cereal yield k.g/hectare	Cereal yield, measured as kilograms per hectare of harvested land, includes wheat, rice, maize, barley, oats, rye, millet, sorghum, and buckwheat. It has been positively affected by labor and fertilizer but negatively affected by land size [57, 59].
Land productivity $\left(\frac{y_{it}}{l_{it}}\right)$	It is the percentage of total cereal yield, measured as kilograms per hectare of harvested land per total arable land per hectare. It is has been negatively associated with cereal crop efficiency [52, 53].
Fertilizer productivity $\left(\frac{y_{it}}{f{e}_{it}}\right)$	It is the percentage of total cereal yield, measured as kilograms per hectare of harvested land per total consumption of fertilizer in kilogram and it has a multiple effect on cereal crop efficiency [64, 83, 85].

Source: From literatures