Effects Of Varietal Differences, Plant Spacing And Weeding Regimes On Weed Density And Yields Of Upland Rice In Uganda

ABSTRACT

Rice is relatively new to Uganda, yet consumption is outstripping production; and with a growing population, demand is likely to increase. NERICA (New Rice for Africa) rice – with high yields and ability to withstand dry conditions is being planted in most part of the country. However, weed infestation is becoming one of the biggest hindrances affecting rice production. The objective of the current work was therefore to investigate the effects of varietal differences, plant spacing and weeding regime on weed density and yields of upland rice in Uganda. A study was carried out during the 2013 cropping season in Mukono agricultural research station and a farmer’s field in Amuru District to evaluate the effects of varietal differences, plant spacing and weeding regimes on weed density and yields of upland rice. The experiment was laid in a Randomized Complete Block Design (RCBD) with Split-split plot arrangement and replicated three times. The weeding regime was the main plot treatment; row spacing constituted the sub-plot while varieties were sub–sub plot. In both sites, the average weed coverage was higher in NERICA-10 (87.8%) followed by NERICA-1 (58.2%) and lowest in NERICA -4 (22.5%). At both sites weed competition reduced rice plant height in NERICA10 (52%) while, NERICA-1 and NERICA-4 had 27% and 15% reduction respectively. Integration of row spacing and weeding reduced weed biomass, with NERICA-4 having highest weed reduction of 89.2% under row spacing of 25cm by 10 cm and 2 hoe-weeding regime(2 and 3 weeks interval), while NERICA-1 and NERICA-10 under same treatment had weed reduction of (67%) and (48%) respectively. Weed competition significantly reduced productive tillers of rice varieties. NERICA-4 produced higher number of productive tiller (84.5%) under row spacing 30 cm by 10 cm and 2 hoe-weeding followed by NERICA-1 (68%) under 25cm and 2 hoe weeding and NERICA-10 (65%) under row spacing of 15 cm by 10 cm and 2 hoe weeding. The data showed that NERICA 4 was more tolerant to weed pressure than the other varieties. Spacing of 25 cm x 10 cm had less weed biomass though 15cm X 10 cm also reduce the weed biomass but had negative result in terms of yield. If farmers were to explore one hoe weeding to control weeds in rice; NERICA-1 should be recommend at a spacing of 30cm x 10 cm to attain an average yield of (2.93tha1 ) which is still above the national average of 1.7t ha-1 . NERICA -4 at single hoe weeding out-yielded other varieties and its yield at two hoe weeding regimes tended to approach optimum.. Its superior yield advantage at single hoe weeding was consistent across locations and is of importance since most farmers are known to avoid a second weeding due to insufficient time and high cost of labor.