Rice is the staple food for more than 65% of population in India. It is cultivated in several agroecological regions. Rice farming is highly widespread and practiced under diversified soil and climatic conditions; hence there are wide variations in variety, methods of cultivation and. soil and water management practices followed. Rice ecosystems in India can be grouped into following categories.
• Rainfed Rice Eco System: (i) Upland
(ii) Low land
• Flood Prone Rice Eco System
Irrigated Rice Eco System:
The total area under irrigated rice in India is about 22 million hectares, which accounts about 49.5% of the total area under rice crop in the country. Irrigated rice is grown in bunded fields; Irrigation is the main source of water in the dry season and is used to supplement rainfall in the wet season. The major irrigated rice-cropping systems in India are rice-rice, rice-rice-rice, and rice-wheat. The average yield is 4–5 t ha-1. Major problems encountered in this production system are yield instability and environmental degradation due to and unbalanced nutrient use, inefficient irrigation water management.
Rain fed Rice Eco System:
Practiced in the areas with rain fall.>1000mm and scope of irrigation is limited. The rainfed rice area is about 24.4 million. The productivity is very low (< 0.98 tones/hectare), due to uncertainty of available water.
Rainfed Upland Rice Eco System
Upland rice area in India is about 6 million hectares which accounts13.5% of the total area under rice crop in the country. The areas lies in eastern zone comprising of Assam, Bihar, Eastern M.P., Orissa, Eastern U.P., West Bengal and North-Eastern Hill region. Upland rice is mostly grown as direct seeded. Fields are unbunded. This is almost a subsistence crop with minimum input. Productivity is very low (< 1ton/ Ha) and unstable due to drought, weeds, light textured and less fertile soil, nutritional imbalances, poor cultural practices, diseases, insects, and a lack of suitable varieties.
Rainfed Lowland Rice Eco System:
It is usually transplanted, and is grown in levelled, bunded fields that retain surface water, but the depth and duration of flooding of the soil varies greatly from year-to-year within a growing season. Depending upon the depth of water it can further classified to shallow water (<50 cm), semi deep water (50-100 cm) and deep water (>100 cm). The water supply is variable, and both drought and flooding may occur in the same season. Rainfed lowland rice system is also classified as favourable, drought-prone, submergence-prone, and drought- and submergence-prone Soil fertility is low and problem soils are common in this ecosystem. Most of the farmers are resource poor. In India, low land rice area is about 14.4 million hectares, which accounts 32.4 % of the total area under rice crop in the country. Production is highly variable.
Flood Prone Rice Eco System
Flood-prone rice is adapted to conditions of temporary submergence of 1-10 days, or long periods (1-5 months) of standing water ranging in depth from 50 cm to 400 cm or more, or daily tidal fluctuations that sometimes may also cause complete submergence. Flooding occurs during the wet season from June to November, and rice varieties are chosen for their level of tolerance to submersion. During the flooding period the land may be fallow or be used for alternative purposes, such as fish and shrimp farming. In India 11.4 % of total rice grown area is flood prone, yields is low (1.5 ton/ha) and variable.
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Sangita Mohanty*, Rahul Tripathi, Mohammad Shahid, Anjani Kumar, V. Kasthuri Thilagam, and A. K. Nayak, Crop Production Division, Central Rice Research Institute, Cuttack-753006