| The experiment was planted at two sites of the station. Table
2, shows the soil and irrigation particulars of both locations. Site
1, irrigated by a fixed line sprinkler system, was subjected to drought
stress by controlling irrigation following seedlings' establishment. The
amount of irrigation water was 55.0% of the Cumulative Pan Evaporation (CPE)
for the same period applied at short interval and shallow depth. In addition,
irrigation was halted for seven days, 65 days after emergence. Site 2, irrigated
by surface flooding was kept free of drought stress. The amount of irrigation
water was 110.0% of CPE given at longer intervals and greater depth (Table
2). Data on number of days to heading, days to maturity and plant height were recorded. The number of tillers or the number of fertile spikes, number of kernels/spike and dry matter weight were obtained from samples collected after 65 days and at harvest. Each sample consisted of all above ground growth from 0.06 m2 area (20 cm of row) of each plot. Grain yield was estimated from the clean grain of the four central rows of each plot. After harvest, the two outer rows of each plot were dug to a depth of 60 cm using a ditcher plow. Ten plants were collected from each plot at random. The roots were thoroughly washed, dried and weighed. Following analysis of variance and L.S.D test, correlation coefficients for each character between the two sites were calculated. Path-Coefficient analysis was carried out to determine the effect of yield component characters on grain yield at different sites. Results Inspection of the plants during different growth stages indicated that poor stand establishment, plant diseases or lodging were not apparent at either site. Therefore, grain yields were related, primarily, to drought stress. Samples collected at 65 days prior to the onset of the severe drought treatment, indicated that the cultivars at site I were under water stress and produced 59.0% less dry matter, 45.0% fewer tillers and headed 3.6 days earlier in comparison to site 2, (Table 3). At the drought-stressed site, 20 cultivars flowered within the seven days period of no irrigation. The rest flowered within the week after irrigation was resumed. The deleterious effects of drought were pronounced on the rapid growing tissues and organs. Spikes failed to emerge from their sheathes as the peduncles ceased to grow and senescence was common on most leaves. In later stages, even when the plants were irrigated regularly, there occurred a rapid termination and final decline in grain development due to enhanced senescence, consequent decrease in photosynthetic activity and reduced transfer of assimilates to the ear. The plants were conspicuously shorter (43.0%) and matured 6.2 days earlier compared to site 2. |
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