الفهرس 
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Abstract
Two pot experiments were conducted: the first experiment to evaluate certain fertilization systems; other experiment was designed for evaluation of both irrigation and fertilization interactions. The two mentioned experiments were carried out under greenhouse conditions.
For the first experiment, the concerned soil was selected from shalakan farm belonging to the Faculty of Agriculture, Ain Shams Univ. as a tillage surface soil (0-30 cm) being then packed in pots having diameter of 25 cm involving 4 kg. Corn (Zea mays L.) (Giza 167 hybrid) was used as a plant indicator. The irrigation during growing season was performed as to always have the soil moisture content at Field Capacity (FC) represented by -0.33 bar water potential evaluated using pressure cooker. Fertilization treatments include two rates of both nitrogen and potassium fertilization equivalent to 50 % and 100 % from the recommended dose by Egyptian Ministry of Agriculture for nitrogen (RDN) and potassium (RDK) applied as ammonium and potassium sulfates, respectively.
Soil samples were subjected to analysis for particle size distribution, which suggested a clay texture; both Field Capacity (FC) at -0.33 bar and wilting point at -0.15 bar were evaluated by pressure cooker and pressure membrane, respectively. Samples of grown plants were taken just before the period of tasselling stage obtained at (60 days) from germination. Fresh weight for both shoots and roots were set after taken of plant samples directly and recorded their fresh weights, dry weight for both shoots and roots were recorded after oven drying at 65 C for 24 hour. The studied plant samples were prepared for determination of total nitrogen along with that of potassium by wet digestion using an acid mixture of sulfuric acid (H2SO4 conc.) and hydrogen peroxide (H2O2 50 %). Both total nitrogen and potassium were evaluated using kjeldahl distillation unit and flame photometer apparatus, respectively. As far as the second experiment was concerned, the selected soil sample from field belonging to Soil Department of Agriculture Faculty, Ain Shams Univ.; the samples, along with that of shalakan farm previously mentioned were generally similar concerning their features. The same irrigation water was used. Indicated samples were subjected to similar analyses. Again, corn hybrid used in the first experiment was adopted for the second mentioned experiment. Irrigation during growing season, were performed as to reach 50, 75 and 100 % FC represented by -0.33 bar water potential. Soil moisture content was maintained throughout the growing season, through weighing every day. Fertilization treatments, included in the second experiment were similar to those of the first experiment.
Both soil and plant analyses, similar to those mentioned in the first experiment were adopted. Both the first and second experiments, were, statistically analyzed using MSTAT program as Randomized Completed Design (RCD).
2. First experiment
1.2. Plant growth parameters
Reponses of plant growth, expressed as both fresh and dry weights (wts.) along with moisture percent for both studied shoots and roots were evaluate.
Results showed positive responses, differences being generally not significant. Treatment of 100 % RDN seemed to be superior for all studied parameters whether shoots or roots were taken in consideration. Potassium fertilization treatments were, again, not significantly effective. In spite of that, superior treatment was obtained with 100 % RDK. Interactions analysis revealed superiority which was obtained with 100 % RDN and 100 % RDK for fresh wts. of both shoots and roots, but 50 % RDN and 100 % RDK for dry wts. for shoots. This was reflected on moisture percent of both shoots and roots; however, superior treatment was observed with 50 % RDN and 50 % RDK for dry wts. of roots.
Reponses of the shoot: root ratio for both fresh and dry wts. as well as moisture percent to fertilization designs were evaluated. Results showed no significancy between the mentioned treatments. Treatment of 100 % RDN seemed to be superior for fresh wts., but 50 % RDN for both dry wts. and moisture percent.
For potassium fertilization treatments, superiority was obtained with 100 % RDK for both fresh and dry wts., but 50 % RDK for moisture percent. The correspondent superior treatment for interaction between fertilization treatments was observed with 50 % RDN and 100 % RDK for fresh wts. which typically reflected on dry wts.; 50 % RDN and 50 % RDK was, however, obtained as a superior treatment for moisture percent.
Similarity between ratio of both fresh and dry wts. Parameters may reflect the similarity of both shoots and roots regarding responses to fertilization treatments of the proposed design.
2.2. Nutrient status
Data representing the status of both nitrogen and potassium, expressed as percentage and total content along with shoot:root ratio in the studied plants, as responded to both nitrogen and potassium fertilization designs are evaluated.
Positive responses were obtained for the differences among either nitrogen or potassium fertilization treatments, including the control; such differences were not significant. Concerning nitrogen fertilization treatments, superior treatment was obtained with 100 % RDN for both nitrogen and potassium status of shoots. As for potassium fertilization treatments, superiority was observed with 100 % RDK for nitrogen percent and potassium status, but with 50 % RDK for nitrogen total content. Interaction analysis revealed a similar trend of non significancy; superior treatment was, however, obtained with 100 % RDN and 50 % RDK for nitrogen status of shoots as well as potassium total content, but with 100 % RDN and 100 % RDK for potassium percent of shoots which was as a superior treatment.
As a conclusion, the mentioned results were relatively different from those obtained with growth of the studied plants. This, again, may reflect the initial relatively ample levels of both indicated elements in the studied soil as to satisfy the requirement needed for development of the studied corn plants. Obtained results showed that indicated responses were generally not significant. The mentioned results are relatively different from those obtained with growth of the studied plants.
Responses of nitrogen status of roots and its shoot:root ratio to both nitrogen and potassium fertilization designs, are studied. In general, results revealed that differences among concerned treatments were not significant. Regarding nitrogen fertilization treatments, superior treatment was observed with 100 % RDN for nitrogen status of roots and its shoot:root ratio. Respecting potassium fertilization treatments, superiority was obtained with 100 % RDK for the nitrogen status of roots, but with 50 % RDK for the shoot:root ratio of nitrogen status. Concerning interactions among nitrogen and potassium fertilization treatments, results showed no significant differences. Superior treatment was obtained with 100 % RDN accompanied with 100 % RDK for the nitrogen status of roots, but 100 % RDN and 50 % RDK for the shoot:root ratio of nitrogen status.
Responses of potassium status of roots and its shoot:root ratio to fertilization designs were evaluated. Results revealed no significant differences among treatments of both potassium status and its shoot: root ratio treatments. With respect nitrogen fertilization treatments, 50 % RDN was superior treatment for potassium status of roots, but 100 % RDN for shoot:root ratio of potassium status.
Respecting potassium fertilization treatments, superior treatment was observed with 100 % RDK for potassium status, but 50 % RDK for shoot:root ratio of potassium status. Concerning superior treatment for interactions among the designed treatments was obtained with 100 % RDN and 100 % RDK for potassium status of roots, but 100 % RDN and 50 % RDK for the shoot: root ratio of potassium status. The mentioned results were relatively different from those obtained with growth of the studied plants, indicated responses being generally not significant. This, again, may reflect the initial relatively ample levels of both indicated elements in the studied soil as to satisfy the requirement needed for development of the studied corn plants.
These results may suggest that relatively low nitrogen fertilization rate was more suitable compared to high rates; on the other hand, high potassium fertilization rate seemed to be more suitable not only for potassium uptake but also for translocation process. Accordingly, the low level from potassium fertilization, opposite to that of nitrogen fertilization is not sufficient for good plant growth under present conditions. This trend was also obtained when both elements when added together; low level of nitrogen along with high level of potassium fertilization seemed to provide good plant growth.
Plant nutrient status and growth parameters for both fresh and dry wts. of shoots were reflected on both total nitrogen content along with both percent and total content of potassium as well as shoot: root ratio. In general, the most suitable rates for both nitrogen and potassium under present condition, was, again, obtained with low level of nitrogen along with high level of potassium fertilization.
3. Second experiment
2.3. Plant growth parameters
Growth may be expressed as fresh and dry wts. along with moisture percent for both shoots and roots, in addition to shoot: root ratio. Responses of plant growth for both shoots and roots to different irrigation and fertilization treatments were evaluated.
As for nitrogen treatments, results showed relative significant differences between the two levels of nitrogen fertilization, superiority was observed with 50 % RDN for fresh wt. for both shoots and roots, but high level that is 100 % RDN treatment was superior for dry wt. along with moisture percent. In spite of no significancy obtained between the two levels of potassium fertilization, for fresh wt. of roots and dry wt. of both shoots and roots along with moisture percent of shoots. Significancy was observed between the indicated treatments for moisture percent of roots. Superiority was observed with 50 % RDK for fresh wt. and moisture of both shoots and roots along with moisture percent of both shoots and roots, but 100 % RDK for dry wts. of both shoots and roots. Concerning the irrigation treatments for plant growth parameters, superior treatments were obtained with 100 % FC regarding fresh wt. for both shoots and roots, 75 % FC for dry wt. parameter as well as moisture percent for both shoots and roots.
Regarding the interactions between both irrigation and nitrogen fertilization treatments, results revealed significant differences among treatments for fresh wt., dry wt. and moisture percent concerning both shoots and roots. Superiority was obtained with 100 % FC and 50 % RDN for fresh wt. of both shoots and roots, 75 % FC and 100 % RDN for dry wt. and moisture percent parameters. Respecting the interactions between both irrigation and potassium fertilization treatments, results showed relatively significant differences among treatments. Superiority was obtained with 100 % FC and 100 % RDK for fresh wt. of shoots; 100 % FC and 50 % RDK for fresh wt. of roots but 75 % FC and 100 % RDK for dry wt. of both shoots and roots.
Superior treatment for moisture percent of both shoots and roots was obtained with 100 % FC and 100 % RDK and 100 % FC and 50 % RDKm respectively. Interactions among irrigation, nitrogen and potassium showed significant differences among. The superior treatment was obtained with 100 % FC, 50 % RDN and 100 % RDK for fresh wt. of shoots, 100 % FC, 50 % RDN and 50 % RDK for fresh wt. of roots but 75 % FC, 100 % RDN and 100 % RDK for dry wt. of both shoots and roots, 100 % FC, 50 % RDN and 100 % RDK for moisture percent of both shoots and roots.
Responses of shoot:root ratio for the studied irrigation and fertilization designs for all growth parameters were studied.
Regarding irrigation treatments, superiority was observed with 100 % FC for the three studied parameters compared to control treatment.
Regarding either nitrogen or potassium fertilization treatments, although, results showed relative significant differences between nitrogen treatments, no significancy was obtained for potassium treatments. Respecting nitrogen fertilization treatments, superior treatments were observed with 100 % RDN for shoots: root ratio of both fresh and dry wts. Along with moisture percent.
Concerning interactions between both irrigation and nitrogen fertilization treatments, results showed that superior treatments were 50 % FC and 100 % RDN for shoot: root ratio of fresh, but 75 % FC and 50 % RDN for dry wts.; values were 75 % FC and 100 % RDN for shoot: root ratio of moisture percent. On the other hand, interactions between both irrigation and potassium fertilization treatments, superiority was obtained with 50 % FC and 50 % RDK for shoot: root ratio of fresh wt., 75 % FC and 100 % RDK for dry wt. along with moisture percent. As for interactions among irrigation, nitrogen and potassium fertilization treatments, results showed relatively significant differences. Superior treatments were obtained with 50 % FC, 100 % RDN and 100 % RDK for the shoot: root ratio of fresh, but 75 % FC, 50 % RDN and 50 % RDK for dry wts.; but a superior treatment was 50 % FC, 100 % RDN and 100 % RDK for the shoot: root ratio of moisture percent.
2.4. Nutrient status
Responses of nitrogen and potassium status, as both percent and total content, to different irrigation and fertilization designs for both shoots and roots were evaluated.
Nitrogen fertilization treatments showed relative no significant differences between treatments opposite to potassium fertilization treatments. Treatment 100 % RDN was obtained as superior for both nitrogen and potassium status concerning nitrogen fertilization treatments. On the other hand, potassium fertilization treatments revealed that superior treatment was 100 % RDK for nitrogen and potassium status. Regarding shoots, irrigation treatments showed that superior treatments were obtained with 50 % FC for nitrogen percent; 75 % FC for nitrogen total content as well as potassium status.
Concerning to interactions between both irrigation and nitrogen fertilization treatments, superiority was observed with 75 % FC and 100 % RDN for nitrogen status; for potassium percent, values were 50 % FC and 100 % RDN, but 75 % FC and 100 % RDN for potassium total content. On the other hand, interactions between both irrigation and potassium fertilization treatments showed relatively significant differences. Superiority was obtained with 50 % FC and 100 % RDK for both nitrogen and potassium percent; 75 % FC and 50 % RDK for nitrogen total content whereas 75 % FC and 100 % RDK was observed with potassium total content.
Concerning interactions among irrigation, nitrogen and potassium fertilization treatments, results revealed significant differences among treatments. Superiority was obtained with 50 % FC, 50 % RDN and 100 % RDK for nitrogen percent, but 100 % FC, 50 % RDN and 100 % RDK for potassium percent, but with 75 % FC, 100 % RDN and 100 % RDK. 100 % FC, 50 % RDN and 100 % RDK for total content of both nitrogen and potassium, respectively.
With respect to roots, results, again, revealed relatively significant differences. Concerning irrigation treatments, superior treatment was obtained with 75 % FC for nitrogen status along with potassium total content, 100 % FC being observed with potassium percent. As for both nitrogen and potassium status of roots, despite results revealing significant differences for nitrogen percent and potassium total content, no significancy was obtained for nitrogen total content and potassium percent. Superior treatment was observed with 50 % RDN for both nitrogen and potassium status. Potassium fertilization treatments revealed relative significancy between treatments. Superiority was obtained with 100 % RDK for nitrogen status, but 50 % RDK for potassium status. As far as interactions among irrigation, nitrogen and potassium fertilization treatments are concerned, results showed significant differences. Superiority was obtained with 50 % FC, 50 % RDN and 100 % RDK for nitrogen percent, 100 % FC, 50 % RDN and 100 % RDK for potassium percent, but with75 % FC, 100 % RDN and 100 % RDK forboth nitrogen and potassium total content.
Responses of the shoot: root ratios for the studied nutrient status were detected.
Nitrogen fertilization designs showed that relative significant differences between treatments, superior treatments were obtained with 100 % RDN for nitrogen percent, but with 50 % RDN for nitrogen total content and potassium status. As for potassium fertilization treatments, the differences between treatments were not significant exception nitrogen total content which was significant. Superior treatment was observed with 50 % RDK for nitrogen status, but 100 % RDK for potassium status. Concerning the irrigation treatments, superior treatments were obtained with 50 % FC for both nitrogen and potassium status. Respecting the interactions between both irrigation and nitrogen fertilization treatments, superiority was obtained with 50 % FC and 100 % RDN for nitrogen status, 50 % FC and 50 % RDN being the superior for potassium status. Regarding the interactions between both irrigation and potassium fertilization treatments, results showed that the superior treatment was 50 % FC and 100 % RDK for nitrogen status as well as potassium status. As for the interactions among irrigation, nitrogen and potassium fertilization treatments, results revealed relatively significant differences. Superior treatments were obtained with 50 % FC, 100 % RDN and 100 % RDK for the status of nitrogen, but 50 % FC, 50 % RDN and 100 % RDK for potassium status.
As a conclusion, sufficiency of 100 % FC treatment seemed to be present, high rates of nitrogen being relatively hazard, with high rates of potassium. This may suggest the sufficiency of 50 % to 75 % FC and 100 % RDK, relatively low rate of nitrogen being required. Finally, the mentioned results refer to that moderate level for irrigation was sufficient for good plant growth, but relatively moderate rates for nitrogen and relatively potassium ones were required.