Abstract:
Experiments were conducted in the Department of Crop, Soil and Pest Management, The Federal University of Technology, Akure to determine the effects of watering and temperature regimes on the growth, seed yield and yield components of three rice landraces and an improved variety. The experiment was a split-plot scheme involving 4 x 3 x 2 factorial combinations of rice varieties (Igbemo, Millina, Cherie and Nerica7), watering regimes, ambient and high temperature conditions arranged in Completely Randomized Design (CRD) with four replications. Watering regimes (40, 70 and 100% field capacity (FC) consisted of water application at 1.5, 1.0, 0.6 litres per pot at 4 days interval) were imposed two weeks after germination. At the onset of flowering, a set of experimental materials grown under the watering regimes were retained under the ambient temperature (29-32ºC) and atmospheric dryness (vapour pressure deficit: 2.3 – 2.8 kPa) and another set were grown under conditions of high temperatures (35-42ºC) and VPD (3.2 - 3.8 kPa: low humidity). Data were collected on root and shoot weights, number of green and senesced leaves at 50% flowering and maturity, number of tillers/stand at 50% flowering and maturity, number of spikelets/panicle, seed and panicle weights. Although the landraces differed in their responses to watering regimes, Millina and Cherie (Benue types) were outstanding in terms of growth, seed yield and yield components. There were 70 and 40% decline in shoot biomass, panicle and seed weights as well as concentrations of chlorophyll and soluble carbohydrates in leaves and stem tissues under 70 and 40 % FC. The low watering (40 %FC) depressed rice vigour of growth and enhanced leaf senescence. The landraces (Igbemo and Benue types) had better tolerance to soil moisture deficit stress at 70 to 40 % FC for number of green leaves and tillers compared with NERICA 7. Moderate and low soil moisture regimes, high temperature and low humidity during reproductive phase resulted in poor seed setting and seed weights, and enhanced leaf senescence, sterility of spikelets, panicles and seeds (empty seeds). Compared with NERICA 7, Igbemo and Benue types had better tolerance of soil moisture deficit and high temperature conditions during reproductive phase. The strong interplay between soil moisture deficit and temperature stress especially during the reproductive phase depressed rice growth and yield. High temperature and low humidity appeared to have accentuated soil moisture deficit constraints on the growth and yield of rice.
