Abstract: Massive organic material input is an effective way to rapidly improve fertility of barren agricultural soil. In this study, we examined the responses of greenhouse gas emissions and soil carbon sequestration from two typical barren cropland soils in a red-soil hilly area to the input of massive granulated organic materials. A field experiment was conducted with a control (CK) and three combinations of granulated organic materials (60 t·hm^-2; input by carbon equivalent for each organic material) in upland and paddy fields, i.e., pure straw (G_S), equal proportions of rice straw and organic manure (G_SM), and equal proportions of rice straw, organic manure, biochar (G_SMB); as well as three amounts of straw granules returned to the field, i.e., 30 (G_S30), 60 (G_S60), and 90 t·hm^-2 (G_S90). The results showed that under the same conditions of material input, CO₂ emissions from upland soil were higher than those from paddy soil, whereas CH₄ and N₂O emissions from paddy soil were higher than those from upland soil. Cumulative CO₂ and CH₄ emissions from upland and paddy soils in one year were much lower under the combination of rice straw, organic manure and biochar than under pure straw and the combination of straw and organic manure. CO₂ emissions in upland soils were much higher under pure straw treatment than under the combination of straw and organic manure, but there was no difference between the two treatments in paddy soils. When 30, 60 and 90 t·hm^-2 pure straw granules were returned to the field, the cumulative CO₂ and CH₄ emissions from upland and paddy soils over one year increased with the return amount. Compared to rice paddy, the proportion of input material carbon converted to soil organic carbon was lower in upland, and the proportion converted to greenhouse gases was higher. However, the proportion of material carbon converted to soil organic carbon remained stable in upland soil and decreased in rice paddy when the amount of material input was increased. In summary, when granulated organic materials are returned to the field, the mixture of appropriate amount of biochar can reduce greenhouse gas emissions and increase soil carbon sequestration in barren croplands. The high-intensity input of organic material granules can be used in uplands. In paddy fields, the input amount should be reduced based on water management of the field, which could reduce greenhouse gas emissions.

Key words: greenhouse gas, organic granulation, straw, organic manure, biochar, cropland soil