Effect of row spacing of Rice transplanter on seedling requirement and grain yield

This study was conducted in the farmer’s field during late boro season (2016) in two villages under Rangpur sadar upazila in Rangpur district of Bangladesh to evaluate the effect of wider spacing of mechanical rice transplanter on the seedling tray requirement and grain yield. The two high yielding rice varieties namely BRRI dhan28 and BRRI dhan48 were transplanted in the farmer’s field by mechanical rice transplanter and compared with hand transplanting. Seedlings density was reduced at the seed rate higher than 145 gm tray-1 indicating higher seed rate increased the seedlings mortality. Seedlings mat prepared by the farmers were varied in seedling height, density and color due to management skill of the respective farmer and irrigation facility in different locations. Seedlings of one square meterarea in tray can transplant 331 square meter area in the field. The varietal difference caused variation of the seedlings density in tray. The rice variety BRRI dhan28 was more preferable to the farmers because of color, density and height of the seedlings in trays. Root formation was better in BRRI dhan48 than BRRI dhan28 and number of seedlings per tray was varied in the same nursery due to variation in germination. Soil settlement in immediately puddled soils influenced the plant to plant spacing. The distance between plants determined the tray requirement in a transplanting operation and controlled by the space setting options depending on the seedlings density in trays. Crop establishment in the field was denser in plots transplanted in the same day (≤6 hrs) of puddling than after one day (<24 hrs). Actual plant spacing setting by machine could not be maintained in the field due to variation of soil type, puddle condition, soil settling time, plow pan and water height. Seedling tray requirement depended on the space setting adjustment and seedlings dispensed per hill in the field. The tray requirement was reduced with higher space setting. Irrespective of space settings in the transplanter, mechanically transplanted rice produced the higher grain yield than the hand transplanted rice. These findings revealed that wider spacing of mechanical transplanter (30 cm) along with tender seedlings helped to increase the grain yield.