The role of croplands in carbon cycling: A review of net ecosystem carbon budget

The Net Ecosystem Carbon Budget (NECB) represents the balance of carbon entering and leaving an ecosystem, thereby determining whether the specific ecosystem is carbon source or sink. This review examines NECB on different croplands of rice, wheat, maize, sugarcane, cotton and sunflower, review highlighting its role on carbon sequestration and climate change mitigation. NECB values vary significantly, ranging from -26460 ± 4587 to 22500 kg C ha-1. Rice cropland systems exhibited positive NECB values (carbon sink) between 572 and 2959 kg C ha-1 under biomass application, while wheat and sugarcane act as carbon sources with values of -4390 ± 105 kg C ha-1 and -26460 ± 4587 kg C ha-1, respectively. Cotton also showed negative NECB (-4940 ± 150 kg C ha-1), whereas sunflower with biochar application achieved 11570.9 ± 334.0 kg C ha-1, compared with control (-19.9 ± 0.6 kg C ha-1). Methodologies such as eddy covariance and static chamber techniques highlighted NECB variability due to environmental and management factors. Although maize under public-private partnership and large-scale farming recorded the highest NECB at 22500 kg C ha-1, similar effective practices such as optimized irrigation, nutrient management and reduced soil disturbance can be practiced in rice cropland systems to enhance their carbon sequestration potential. Moreover, NECB varies across ecosystems and soil types, affecting whether croplands act as carbon sinks or sources. Adapting management practices to local environmental conditions is crucial for improving NECB across different crop systems and achieving sustainable agriculture and climate mitigation goals.