الفهرس 
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Abstract
Two field experiments were carried out at the Experimental Farm of the Rice Research and Training Center (RRTC), Sakha, Kafr El-Sheikh, Egypt, during 2008 and 2009 seasons to study the effect of phosphorus levels and potassium application management on productivity of hybrid rice one cultivar. The study was conducted under transplanting conditions and under preceding crop wheat. Phosphorus levels were 0, 18, 36 and 54 kg P2O5/ha and the eight different potassium treatments were i.e.,
T¬1 : 0 K
T2 : All K basal
T3 : ½ K at panicle initiation + ½ K at late booting
T4 : ½ K basal + ¼ K at panicle initiation + ¼ K at late booting.
T5 : ½ K basal + 2% spray of K2O solution at panicle initiation.
T6 : ½ K basal + 2% spray of K2O solution at late booting.
T7 : ½ K basal + 2% spray of K2O solution at panicle initiation + 2% spray of K2O solution at late booting.
T8 : 2% spray of K2O solution at panicle initiation + 2% spray of K2O solution at late booting.
A split plot design with four replications was used. The four phosphorus levels were arranged in the main plots, while, the eight different potassium treatments were located in the sub-plots. The planting dates was 10th of May in both seasons. Thirty days old seedling was transplanted with 3 seedling/hill. The studied characters were as follows
Growth characters:
1. Plant height (cm).
2. Leaf area index.
3. Dry matter accumulation (g/m2)
4. Number of tillers/m2
5. Leaf chlorophyll content (SPAD value)
B. Yield and yield attributes:
1. Number of panicles/m2.
2. Panicle length (cm).
3. Panicle weight (g).
4. Number of branches per panicle.
5. Number of total grains per panicle.
6. Number of filled grains per panicle.
7. Filled grains percentage.
8. 1000-grains weight (g).
9. Grain yield (t/ha).
10. Straw yield (t/ha).
11. Harvest index.
C. Grain quality characters :
1. Hulling (%).
2. Milling (%).
3. Head rice (%).
4. Grain protein (%).
D. Nitrogen, phosphorus and potassium concentration:
1. Nitrogen (%) in grains and straw.
2. Phosphorus (%) in grains and straw.
3. Potassium (%) in grains and straw.
The main results obtained from this investigation could be summarized as follows:
A. Growth characters:
Mean values of plant height (cm), dry accumulation, leaf area index, number of tillers per m2 and leaf chlorophyll content (ppm) at flowering stage were significantly increased by application of phosphorus fertilizer levels in the two rice seasons. Plants received 36 kg P2O5/ha significantly increased as compared with the unfertilized plants by phosphorus (0 kg P2O5/ha).
Adding potassium fertilizer as ½ basally + 2% spray of K2O solution at both panicle initiation and late booting stages (K7 treatment) significantly recorded the maximum values of plant height (cm), dry matter accumulation, leaf area index, number of tillers per m2 and leaf chlorophyll content (ppm) during both 1st and 2nd seasons, followed by K4 treatment (1/2 K B + ¼ K at PI + ¼ K at LB). On the other hand, the lowest values were produced with K1 treatment (without potassium application).
The interaction effect between phosphorus levels and potassium fertilizer treatments had a highly significant effect on plant height, dry matter accumulation, leaf area index, number of tillers per m2 and leaf chlorophyll content during both seasons. The maximum values were obtained when phosphorus applied at the rate of 36 kg P2O5/ha combined with K7 treatment (1/2 K basal + 2% spray of K2O solution at both PI and LB stages). While the lowest values were found when no phosphorus and potassium were applied.
B. Grain yield and yield attributes:
Phosphorus levels significantly affected grain yield and yield attributes i.e. number of panicles/m2, panicle length, panicle weight, number of branches per panicle, number of total grains per panicle, number of filled grains per panicle, filled grains percentage, 1000-grains weight, straw yield and harvest index. Increasing phosphorus levels from 0 up to 36 kg P2O5/ha significantly increased grain yield and yield attributes. When phosphorus was applied at the rate of 36 kg P2O5/ha the greatest grain yield and yield attributes were obtained, while the lowest values were obtained at zero phosphorus application.
Adding potassium fertilizer as ½ basally + 2% spray of K2O solution at both PI and LB stages (K7 treatment) recorded the maximum values of grain yield and yield attributes i.e. number of panicles/m2, panicle length, panicle weight, number of branches per panicle, number of total grains per panicle, filled grains percentage, 1000-grains weight, straw yield and harvest index, followed by K4 treatment (1/2 K basal + ¼ K at PI + ¼ K at LB). Generally, the lowest values of the above mentioned traits were obtained at K1 treatment (unfertilized treatment).
Phosphorus levels x potassium treatment interaction had a highly significant effect on grain yield and yield attributes in both seasons. In general, the rate of 36 kg P2O5/ha combined with K7 treatment (1/2 K basal + 2% spray of K2O solution at both PI and LB stages) gave the highest values of yield and yield attributes under study, while zero P2O5/ha gave the lowest ones at K1 treatment (control).
C. Grain quality characters:
The application of phosphorus fertilizer had a markedly increase in hulling, milling, and head rice percentage as well as grain protein content in the two seasons. Increasing phosphorus rates from 0 up to 36 kg P2O5/ha significantly increased the above mentioned traits. The highest values of hulling, milling and head rice percentage were produced from the rate of 36 kg P2O5/ha. While, the highest values of grain protein content were obtained from the rate of 54 kg P2O5/ha. On contrast, the lowest values of hulling, milling and head rice percentage as well as grain protein content were belonged to unfertilized treatment (zero phosphorus) control.
The maximum percentages of hulling, milling, head rice and grain protein content were produced when potassium fertilizer was added as ½ basally + 2% spray of K2O solution at both PI and LB stages (K7 treatment), followed by ½ K basally + ¼ K at PI stage + ¼ K at LB stage (K4 treatment). In contrary, K1 treatment (unfertilized treatment) recorded the lowest percentages of hulling, milling, head rice and grain protein (%) in both first and second seasons.
Phosphorus rates x potassium treatments interaction had a highly significant effect on the percentages of hulling, milling, head rice and grain protein content in both seasons. While, the rate of 36 kg P2O5/ha gave the highest percentages of hulling, milling and head rice with K4 treatment. Zero P2O5/ha gave the lowest ones at K1 treatment (control). Moreover, the rate of 54 kg P2O5/ha gave the highest values of grain proteins content with K7 treatment and the lowest ones were recorded by zero P2O5/ha at K1 treatment (unfertilized treatment).
D. Nitrogen, phosphorus and potassium determination:
The application of phosphorus fertilizer to hybrid rice 1 cultivar had a markedly increase in nitrogen, phosphorus and potassium content in rice grains and straw. Increasing phosphorus levels up to 54 kg P2O5/ha significantly increased the above mentioned traits, followed by the rate of 36 kg P2O5/ha in both seasons. However, the lowest content of nitrogen, phosphorus and potassium was obtained with unfertilized treatment (control) no phosphorus applied.
Nitrogen, phosphorus and potassium content in rice grains and straw were linearly higher by the application of potassium fertilizer. The maximum content was found when potassium applied as ½ basally + 2% spray of K2O solution at both panicle initiation and late booting stages. While, the minimum content of nitrogen, phosphorus and potassium in rice grain and straw were obtained at K1 treatment (control) unfertilized treatment.
Phosphorus levels x potassium treatments interaction showed a highly significant effect on nitrogen, phosphorus and potassium content in rice grains and straw in both seasons. where the rate of 54 kg P2O5/ha gave the highest content with K7 treatment. Zero phosphorus (P2O5/ha) gave the lowest ones at K1 treatment (control) no phosphorus and potassium were applied.