Rice is the single most important crop in Assam. It occupies 2.54 million ha of the gross cropped area of 4.16 million ha and contributes 96% of the total food grain production of the state. Assam is very well-recognized for its rich rice genetic diversity. Cultivation of rice under diverse agro ecological conditions over the years has resulted in the development of a multitude of strains with specific adaptations through natural selection and farmers’ discretion. The physical features, geographical location and historical realities have made the state an area of unique diversity and ethnic migration and immigration to the state over the years have led to the introduction of different types of rice genetic stock.
The agro-climatic variation, seasonal variation in temperature and rainfall and agriculture dependence on natural precipitation have resulted in three rice-growing seasons in the state. The rice germplasm of Assam is classified on the basis of growing season, crop duration, land and hydrological characteristics, seeds’ size and shape a, aroma, and endosperm characteristics. In recent times, modern photo period sensitive varieties of different durations are being widely grown and the irrigation facilities are being increasingly utilized for rice cultivation in the state.
Ahu (Autumn rice) grown during March / April – June / July. These rice germplasms are photo-period insensitive, early maturing (80-130 days) and are grown under variable water depth. The varieties can be sub-grouped into two: one grown direct- seeded under upland situations with natural precipitation and other transplanted with or without irrigation. The direct seeded varieties relatively earlier in duration than the transplanted. In Barak valley the direct seeded Ahu rice are further classified as dumai, murali and chengri mainly depending on duration; with Dumai being the earliest (80-90 days).
Sali rice (Winter rice) is grown during June/July - Nov/ Dec. The indigenous rice varieties are belonging to this group are photo-period sensitive, tall, late maturing (150-180 days) and grown, generally transplanted under variable water depth. In Brahmaputra Valley these are further classified as Sali, Lahi, Joha, Bora and Chokuwa, based on the grain characteristics. The varieties belonging to Sali subgroup are course grained and are considered to be relatively better adapted to low lying areas. The Lahi varieties are medium, slender grained ( Fine), and relatively better-adapted to medium land situation. The Joha varieties are fine-grained with characteristic aroma. Bora varieties also called Birain in Barak Valley, are sticky which are used for making various kinds of breakfast foods including “soft rice” and Chokuwa rice.
Asra (semi-deep water) is grown during April/May – Dec/Jan. Asra varieties are grown, broadcast, or transplanted in the low-lying areas where the water depth can be up to 100 c.m. during the life cycle of the crop. These varieties are sown along with Ahu rice and harvested at the time when Sali rice is harvested, thus taking about 240-270 days from sowing to maturity. Based on the time of their harvest these varieties can be considered to be part of the Sali season rice.
.jpg)
Bao rice is grown during April/ May – Dec/ Jan. These varieties are normally, grown broadcast, occasionally transplanted in the low-lying areas, adapted to deep-water situations enduring water depth more than 100 cm. Like Asra varieties these are also sown at the time when Ahu rice is sown and harvested at the time when Sali rice is harvested to take about 270 – 300 days to harvest. These varieties are also considered part of Sali season rice.
Boro (summer rice) is traditionally grown during Nov / Dec – May / June. These are photo-period insensitive, grown transplanted traditionally in the beel and marshy land situations with minimum or no tillage. Due to low temperature stress during the vegetative phase these varieties take long duration to mature (170- 200 days).
It is grown direct-seeded in Jhum land as a major component of mixed cropping on slope lands or grown direct-seeded or transplanted in terrace and valley during April- Sept. These varieties take about 140-160 days from sowing to harvesting.
Jorhat, PIN - 785013 Assam