This study conducted a life cycle assessment of new techniques and approaches in rice paddy cultivation. We evaluated reclaimed land in Hachirogata, located in Japan’s Akita Prefecture. Non-puddling cultivation is a technique of planting rice without the puddling. A rotary plow is used to plant the rice in finely crushed soil. Non-puddling allows a delay in irrigation. Thus, the soil is less likely to become deoxidized and a smaller amount of methane gas is released from the disturbed soil. Sparse planting is a technique whereby the planting stalk density is reduced by 30% (21 stalks/m² to 15 stalks/m²), thereby reducing the material costs of producing seedlings. We found that use of the non-puddling technique reduced overall GHG emissions to 69% of those produced by rice cultivation using puddling. With sparse planting, GHG emissions were only reduced by a small amount to 93% of that of full planting. The current work shows that the appropriate mixture of sparse planting and non-puddling cultivation is necessary to obtain the greatest reduction in GHG emissions.