الفهرس 
Water relations of riceOnly 14 pages are availabe for public view
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Abstract
Four field experiments were conducted at the farm of the Rice Research & Training Center (RRTC), Sakha, Kafr El-Sheikh, Egypt during 1994 and 1995 seasons. The main objectives of this investigation wereto study the effect of irrigation treatments, time of nitrogen application and potassium levels on some growth attributes, yield and its components, chemical and technological properties as well as some rice water relations of Giza 176 rice variety. A split plot design with four replications was used. The main plots in all experiments were devoted to the four irrigation interval (continuous flooding, irrigation every 6, 9 and 12 days ). The subplots in the first two experiments were occupied by the three time of nitrogen application, single dose as basal, two splits (2/3 as basal + ’13 at panicle initiation) and three splits (’13 as basal + ’13 at maximum tillering + at panicle initiation). While the sub plots in the other two experiments, with the sm~e irrigation interval as before, were asigned for three potassium levels (0, 57, 114 kg K20/hectare). Growth analysis was determined on interval of 15 days, samples of rice plants were collected at four dates 40, 55, 70 and 85 days after transplanting. A sub plot area of 10.5 m2 was devoted for yield determinations. The main results obtained from this investigation can be summarized as follows : 1- Effect of Irrigation Treatments and Time of Nitrogen Application on : 1 - Growth analysis and attributes : Irrigation treatments had significant effect on the most characters under investigation. Plant height, dry matter production, leaf area index and crop growth rate were significantly affected by the irrigation interval, they were decreased as irrigation interval increased in both seasons in all sampling dates, while, relative growth rate was significantly affected by irrigation interval at the second and third sampling dates in 1995 season only. The highest values of all traits were obtained when plants were subjected to continuous flooding or irrigated every 6 days, then it decreased as the irrigation interval increased up to 12 days . In both seasons continuous flooding gave earlier heading than other irrigation treatments, while irrigation every 12 days caused a delay in heading date. In 1994 season, time of nitrogen application caused significant effect on plant height at 40 days after transplanting (DAT), dry matter production at 70 and 85 DAT and relative growth rate at first and second periods, while, leaf area index and crop growth rate was not effected by the different treatments. On the other hand, in 1995 season, there were significant effect on plant height, crop growth rate and relative growth rate at last sampling dates, while, dry matter production and leaf area index were significantly affected by the different treatments at 70 and 85 DAT. In both seasons, adding nitrogen in two or three splits recorded higher values of these traits in all sampling dates than single dose as basal. Adding nitrogen in three splits significantly delayed plant heading compared with single dose application. 2- Yield and its components : Irrigation treatments had significant effect on yield and most of its components. Continuous flooding, followed by irrigation every 6 days gave the maximum number of tillerslm2, number of panicles/m2, panicle length, brancheslpanicle, number of filled grainlpanicle, unfilled grain %, panicle weight, 1000-grain weight, grainlstraw ratio, grain yield and straw yield tlha, with no significant difference between each other in most traits studied. Over both season, grain yield was 9.66, 9.42, 6.70 and 5.57 todha and straw yield was 1 1.55, 1 1.28, 9.13 and 8.38 tonlha, for continuous flooding, 6, 9 and 12 days irrigation interval, respectively. Regarding time of nitrogen application, results showed a significant effect on most studied characters of yield and its components. Splitting nitrogen dose into two or three splits gave higher number of tillerslm2, number of panicles/m2, panicle length, brancheslpanicle, number of filled graidpanicle, panicle weight, 1000- grain weight, graidstraw ratio and grain yield (todha) than single dose of nitrogen. Over both seasons, grain yield was 7.37, 8.04 and 8.10 t/ha, when nitrogen was added in single dose, two and three splits, respectively.