Abstract
A study was carried out at the net house and Field Laboratory of the Department of Agronomy, Bangladesh Agricultural University, Mymensingh to find out the effects of different soil moisture regimes on growth, yield and nutrient uptake of three modern varieties of rice transplanted during the rabi season (November- April) of 1995-96, 1996-97 and 1997-98. In case of pot experiments there were nine different soil moisture regimes while in field experiment there were four soil moisture regimes. The experiments were laid out in randomized complete block design.
In both the pot study and field experiments, high soil moisture tensions (saturation to 0.3 bar tension and saturation to 0.5 bar tension) throughout the growth period significantly reduced yield and yield contributing characters of boro rice. The physiological parameters like DM, LAI, CGR, RGR, NAR, RWC, chlorophyll a and chlorophyll b content were also significantly affected by soil moisture regime. Saturation to 0.3 bar and saturation to 0.5 bar tension soil moisture throughout the growth period significantly affected the RLD, RV, RDW and R:S ratio.,
In the pot study, evapotranspiration (ET) (ml/pot/day) was highest in plants grown under continuous submergence (To) and lowest under saturation to 0.5 bar tension throughout the growth period (T3) in both the years. Similarly, water use efficiency (gdm/kg water) was highest under continuous submergence (To) and lowest under saturation to 0.5 bar tension (T3) throughout the growth period.
The total water requirement was maximum (135.49cm) under continuous submergence (To) and the minimum (66.12cm) under saturation to 0.5 bar tension (T3). Under continuous saturation (T1), there was a saving of 17.49% water with 6.72% yield reduction compared to that in continuous submergence (To). The mean WUE was found to be highest (40.62kg/ha/cm) under saturation to 0.5 bar tension and the lowest (34.20 kg/ha/cm) under continuous submergence throughout the growth period. (To).
Nutrient uptake (N, P, K and S) was closely related to the yield of rice. Nutrient uptake (N, P, K and S) and grain growth rate were highest in plants grown under continuous submergence (To) and the lowest under saturation to 0.5 bar tension throughout the growth period (T3).
Among the varieties under study, the highest grain yield was obtained in BR14 and the lowest in BR3. Grain yields in plants grown under saturation to 0.5 bar tension throughout the growth period (T3) reduced drastically due to lowest number of fertile tillers/hill, shortest panicle with lowest number of grains/panicle and lowest 1000 grain weight.
Variations in morphological alterations of rice spikelets were observed under different soil moisture regimes. Among the tested varieties, hypoplasia of glume, lodicule, stamen, stigma and ovary had a strong positive correlation with spikelet sterility