ABSTRACT
The rice (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping system is extremely important for food security in Nepal. In the early 1960s, the rice-wheat system occupied 0.1 million hectares. With the advent of new high-yielding, fertilizer-responsive, short-duration rice and wheat genotypes in the early 1970s, growing rice and wheat in sequence became feasible. Today, this system constitutes the major cropping system in the terai and midhills of Nepal, covering 0.52 million hectares (Table 1) (Pandey et aI., 2001). In spite of Nepal's having adopted this system, the productivity level remains low. The major constraint to expansion of the rice-wheat area and increased yield is late planting caused by the short period available for sowing of wheat after rice and the availability of yearround irrigation (Harrington et aI., 1993). The average yield of rice rarely exceeds 3 t ha - 1 and wheat yield varies from 1 to 2 t ha - 1. These yields are low compared to other rice-wheat-growing countries in the region. However, rice-wheat system yields of 9 t ha - 1 have been reported by some farmers in the midhills especially near Kathmandu and in the Kavre District. This indicates a large gap between the potential and actual yields of the rice-wheat system, and research is needed to close this gap.
