Abstract
Four field experiments were conducted at the Hajee Mohammad Danesh Science and Technology University Farm, Dinajpur in aman seasons (July-December) of 2004, 2005 and 2006 with a view to studying the effects of different cultural practices on the yield and quality of aromatic rice. All the experiments were laid out in randomized complete block design. The first experiment was conducted in 2004 to determine the optimum transplanting date in respect to yield and quality of aromatic rice varieties. The experiment consisted of six transplanting date from 15 July to 3 September with 10 days intervals and eight varieties viz., Kataribhog, Radhunipagal, Chinigura, Badshabhog, Kalizera, BRRI dhan34, BRRI dhan37 and BRRI dhan38. It was observed that transplanting date significantly influenced the grain yield. All the varieties transplanted on 15 July gave highest grain yield except Kalizera, which produced highest grain yield on 25 July. Grain yield decreased gradually with the delayed in transplanting dates. Highest but identical grain yield was obtained from BRRI dhan34, Kataribhog and Badshabhog on 15 July transplanting. The estimated optimum transplanting time of Kataribhog 15-25 July, Radhunipagal 15-20 July, Chinigura 15-21 July, Badshabhog 15-22 July, Kalizera 18-25 July, BRRI dhan34 15-20 July, BRRI dhan37 21-31 July and BRRI dhan38 18-26 July to get higher yield in aman season. Aromatic rice transplanted on 25 July to 14 August produced significantly better quality grain in terms of high milling outturn, head rice outturn and grain length. Delayed transplanting increased the protein content in brown rice. Among the varieties, Badshabhog had the highest milling and head rice outturn. Highest protein and amylose content were found in Kalizera and BRRI dhan34, respectively. Badshabhog and Kalizera were strong in aroma but other varieties were moderate type. BRRI dhan37 and BRRI dhan38 were medium slender shape. The second experiment was conducted in 2005 to determine the suitable planting method. Three planting methods viz., Direct seeding, Transplanting and Double transplanting were included as the experimental treatment. Three varieties namely, Kataribhog, Badshabhog and BRRI dhan37 were used as experimental crops. Method of planting had significant influence on grain yield. Highest grain yield was obtained from transplanting method. The variety BRRI dhan37 and Kataribhog produced highest grain yield from transplanting method whereas Badshabhog gave the highest grain yield under double transplanting method. Double transplanted and transplanted aromatic rice produced significantly better quality grain than direct seeding method in terms of high milling outturn, head rice outturn, protein and amylose content. Length breadth ratio and volume expansion ratio were significantly higher under double transplanting method than transplanting. The third experiment was conducted in 2005 to evaluate the effects of organic and inorganic fertilizers on the yield and quality of rice varieties. Highest grain yield was obtained from recommended NPKSZn fertilizers + green manure with Sesbania rostrata @ 15 t ha⁻¹. Yield attributes such as plant height, total tillers hill⁻¹, fertile tillers hill⁻¹, panicle length and grains panicle⁻¹ showed higher values with the incorporation of green manure in combination with recommended dose of chemical fertilizers. BRRI dhan38 produced the highest grain yield when recommended NPKSZn fertilizers were applied with green manure (Sesbania rostrata) @ 15 t ha⁻¹. The amylose content of rice considered as the main parameter of cooking and eating quality, which increased significantly due to application of organic fertilizer. Application of green manure (Sesbania rostrata) @ 15 t ha⁻¹ with recommended NPKSZn fertilizers produced significantly better quality grain than NPKSZn fertilizers application in terms of high milling outturn, head rice outturn, volume expansion ratio and amylose. Grain elongation ratio was better under the sole application of manures as cow dung @ 10 t ha⁻¹ and green manure (Sesbania rostrata) @ 15 t ha⁻¹. Highest protein in brown rice was found in recommended chemical fertilizer (NPKSZn) dose. The effect of harvesting time on the yield and quality of aromatic rice was evaluated in the 4th experiment in 2006. The experiment consisted of three harvesting time viz., 25 days after flowering (DAF), 30 DAF, 35 DAF and three rice varieties namely, Kataribhog, Badshabhog and BRRI dhan34. Significant variation was found due to interaction of harvesting time and variety. Highest grain yield were obtained from second harvest (30 DAF) for BRRI dhan34 and Badshabhog but Kataribhog was highest at third harvest (35 DAF). The aromatic rice harvested at 30-35 DAF was found to be suitable for higher grain yield and quality in respect of head rice outturn and grain elongation ratio.