Abstract

                                The root distribution patterns of high yielding rice varieties (IR 8. IR 20, IR 22. Co 29. TKM 6. ADT 27, Co 33. Co 34. Co 35. Co 36 and Bhavani) in their natural habitat in fields using pt plant injection technique were studied. The results revealed that 55 to 75 per cent of roots were concentrated in the soil zone covered by 10 cm lateral distance and 16 cm depth from the base of the plant and 80 to 85 per cent in the soil zone covered by 15 cm lateral distance and 24 cm depth. Heading stage was found to be the best stage for taking soil-root core samples for evaluating the root distribution pattern. Slight variations were observed among varieties in the percentage root distribu- tion in the soil zone covered by 10 cm lateral distance and 16 cm depth but the root distribution in the soil zone covered by 15 cm lateral distance and 24 cm depth was almost same for all the varieties. Neither nitrogen levels nor different spacings of planting influenced the root distribution. The method of phosphorus application either broadcasting after last ploughing or broadcasting before last ploughing also had no influence on the rooting pattern of the rice crop.

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