Diversifying rice systems in rotation with other cereals like wheat or maize, high-value crops like potato, legumes, or fodder crops is one way rice farmers can optimize their use of resources. Diversified cropping systems broaden the source of a farmer's food and income, increases their land productivity, and minimizes unpredictable risks such as the build-up of pest and diseases common in rice monoculture.
Owing to market forces, rice-based cropping systems in irrigated and otherwise favorable environments in Asia and Africa – those are areas with sufficient rainfall, good soils, and good market access – are continuously being intensified to include wheat and maize. Rice-wheat systems presently occupy 13.5 million hectares in South Asia’s Indo-Gangetic Plains and another 3.5 million hectares in China. Rice-maize systems are also gaining importance in South and Southeast Asia.
The increasing demand for maize in many Asian countries has led to diversifying rice-rice or rice-wheat systems into rice-maize systems that may also occupy up to 3 million hectares at present. In addition, rice is also grown with other crops like potato, legumes, or vegetables in about 8 million hectares.
Due to continuous long-term rotations and the soil going through cycles of wetting and drying, cereal-based systems, particularly the rice-wheat systems, have shown stagnating and declining yield and productivity. Rice-wheat systems are becoming more and more unsustainable because of:
- Changing climate;
- Degrading or depleting natural resources like water, soil, and biodiversity;
- Inefficient use of inputs like fertilizers, pesticides, and labor;
- Soil, water, and air (or the environment collectively) pollution; and
- Fast-changing socio-economic conditions (population growth, increasing poverty, less rural-urban migration, increasing labor scarcity).
To help improve the productivity and sustainability of diversified cropping systems, IRRI along with many partners is developing and diffusing integrated crop and resource management technologies that follow the principles of conservation agriculture. This includes:
- Laser leveling;
- Residue management to avoid burning;
- Additional crop during fallow;
- Direct drill-seeding after zero-tillage on flat or raised beds to reduce turnaround time between crops;
- Water-saving irrigation; and
- Site-specific nutrient management guidelines and technologies.
IRRI is also looking into more profitable crop rotations through higher-value crops-based systems like potato, mungbean, pigeonpea and other crops used in rice-wheat rotations.
This is a very interesting a rice-maize crop rotation experiment that was started in 1993 on the research station of IRRI.