Rice, maize, and wheat are major cereals contributing to food security and income in South Asia. These crops are grown either as a monoculture or in rotations in tropical and sub-tropical environments of South Asia. In the irrigated and favorable rainfed lowland areas, rice-rice (R-R), rice-wheat (R-W), and rice-maize (R-M) are the predominant cropping systems. Rice-wheat systems provide the staple grain supply for about 8% of the world’s population, making these systems critically important for global food security. In South Asia, rice-wheat systems produce more than 30% of the rice and 42% of the wheat consumed and cover about 14 million hectares of cultivated land, with most of the area located in India and the IGP. Rice (Oryza sativa L.) and maize (Zey mays)are grown in 3.5 million hectares (Mha) in Asia that includes 1.5 Mha in South Asia.Area under rice-wheat system is greater than that in rice-maize system. Area under conventional is greater than area under conservation agriculture. The conventional agriculture has many drawbacks than conservation agriculture. There is a greater opportunities of conservation agriculture in near future in Nepal. However, there are challenges too for developing site specific RCTs and its adoption by uneducated farmers.There are very few researches done in rice-maize system under CA. Research has shown that for sustainability in agriculture horizontal expansion of yield can be done by adopting multi cropping system(R-W,R-M) than monoculture of rice, wheat and maize and vertical expansion can be done by adopting the RCT(conservation agriculture).