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008			021226s2001 th uzm rtt 00| a1eng d
035			_a.b11871957
099		9	_aAIT Thesis no. AS-01-13
100	0		_aLe Thi Hoa Sen
245	1	4	_aThe effects of depth of water on growth, yield and weed competition in rice
260			_aBangkok : _bAsian Institute of Technology, _c2001
300			_a47 leaves
490	1		_aThesis ; _vno. AS-01-13
500			_aA thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of environment, Resource and Development
502			_aThesis (M.Sc.) - Asian Institute of Technology, 2001
520			_aWeeds constitute a group of plants growing where they are not wanted. In lowland rice, grasses, sedges and broad leaves grow and compete with rice for light, nutrient, space and water. Weed infestation primarily constrains rice production by reducing grain yield. In order to control weeds in rice, several weed control methods were discovered. However, rice growers still face many difficulties in solving weed problems. Water management is an indigenous method for controlling weeds in rice. This study was therefore conducted to find out an effective weed management practice to assist rice growers. The preliminary laboratory study confirmed that the depth of water at 0 cm and 2 cm were favorable for rice seed germination and emergence. The water depth above 2 cm reduced germination of rice seeds. In submerged conditions, rice population was reduced, and establishment was little late The highest number of tillers was produced at water depth between 4 and 6, while the lowest at 0 and 2cm. The latter caused heavy weed growth and casualties to rice plants. Removal of weeds at 35 DAS caused significant increases in growth and yield of rice. Number of grains per panicle remained unchanged above 4 cm. There was a reduction of number of productive grains per panicle at 0 and 2 cm. However, removal of weeds at 35DAS reduced the casualties. The 100-grain weight remained unchanged at the depth of water above 4 cm and in the two control treatments. The highest hundred-grain weight was shown at 6 and 8cm. Grain yield of rice increased with increasing the depth of water from 0 to 4 cm, but yield was not significantly different at water depths from 4 to 8 cm without removal of weeds at 35 DAS. When weeds were removed at 35 DAS, there were no yield differences with increasing water depth from 0 to 8 cm. Although yield parameters showed their highest values at different water depths, the optimum conditions for the combined effect on increasing the final grain yield were found between 4 to 6 cm depths.
650	1	0	_aRice _xWeed control
650	1	0	_aWater in agriculture
650	1	0	_aRice _xIrrigation
700	1		_aRanamukhaarachchi, S.L., _eChairperson
700	1		_aZoebisch, Michael A., _eExamination Committee
700	1		_aShivakoti, Ganesh P., _eExamination Committee
710	2		_aSwedish International Development Agency (Sida), _eScholarship donor
810	2		_aAsian Institute of Technology. _tThesis ; _vno. AS-01-13
856			_3Full-Text _uhttp://203.159.5.9/ait-thesis/detail.php?q=B07816
907			_a.b11871957 _bmnait _cu
902			_a240403
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