الفهرس 
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Abstract
The present study was conducted at the Agricultural Research and Experiment Station, Faculty of Agriculture, Minia University. located in the western edge of Samalout, El-Minia Governorate, Egypt.
The study was carried out during two growth seasons (2004/2005 and 2005/2006) on potato crop (Solanum tuberosum L.) cultivar Diamont grown in a clay loam soils to investigate the effect of applying different levels of nitrogen and potassium fertilization on:
Potato growth, yield, quality, nutrients concentration in the potato plants and nutrients uptake by the potato plants.
The experiment was designed in a randomized complete block design with four replications. The experiment included two factors, the level of nitrogen and the level of potassium, singly or in combination, making a total number of 25 treatments as follows:
1- Control.
2- Four levels of nitrogen fertilization [100, 150, 200 and 250 kg N /feddan] added in the form of ammonium nitrate.
3- Four levels of potassium fertilization [75, 100, 125 and 150 kg K2O /feddan] added in the form of potassium sulphate.
4- Combination of the four levels of nitrogen fertilization and the four levels of potassium fertilization.
The experimental design was consisted of 100 plots. The size of each plot was 10.5 m2 (3.5 x 3.0 m2), Row spacing in each plot was 40 cm. The distance between hills was 20 cm.
The obtained results could be summarized as follow:
1. The effect of nitrogen and potassium fertilization on the soil.
• Addition nitrogen to the soil resulted in a significant increase in the soil nitrogen content.
• Applying potassium to the soil resulted in a significant increase in the soil potassium content.
• Soil phosphorus content was not affected by nitrogen or potassium fertilization.
• Both nitrogen and potassium significantly increased the soil (EC) and decreased the (pH).
2. The effect of nitrogen and potassium fertilization on the growth of potato plant.
Plant height.
The plant height of potato was significantly increased due to increasing nitrogen and potassium fertilization level and their interaction in the two growing seasons.
Number of stems per plant.
Addition nitrogen or potassium fertilizers and their interaction gave significant increase in the number of stems/plant.
Shoots fresh and dry weight.
Applying nitrogen or potassium fertilizers and their interaction gave significant increase in fresh and dry weight of the shoots in the two growth seasons.
Leaves fresh and dry weight.
The fresh and dry weight of potato leaves were significantly increased due to increasing nitrogen or potassium fertilizers and their interaction in the two growth seasons.
3. The effect of nitrogen and potassium fertilization on the yield of potato plant.
Number of tuber per plant
Addition of nitrogen or potassium fertilizers and their interaction significantly increased the number of small, medium and large size tuber/plant in the two growth seasons.
Graded weight of tubers in ton per feddan
Applying nitrogen or potassium fertilizer and their interaction significantly increased the Graded weight of small, medium and large size tubers in the two growth seasons.
Yield fresh and dry weight
Applying nitrogen or potassium fertilizers and their interaction gave significant increase in the tuber fresh and dry weight in the two growing seasons.
4. The effect of nitrogen and potassium fertilization on mineral content (N, P, K) of potato plants.
Applying nitrogen or potassium fertilizers and their interaction resulted in significant increases in NPK concentration in tubers, shoots and leaves of potato plants in the two growth seasons.
5. Nutrient uptake by the potato plants
NPK uptake of potato plants was significantly increased by increasing nitrogen or potassium fertilizers and their interaction in tubers and shoots.
6. Nitrogen use efficiency by potato plants
Increasing ammonium nitrate resulted in decreasing nitrogen use efficiency by potato plant in the two growth seasons.
CONCLUSIONS
Within the limitations of the current study, it may be safe to draw the following conclusions:
1- In situations similar or close enough (in climatic, economic and soil conditions) the application of 200 Kg N and 150 Kg K2O per feddan may give the optimum yield.
2- This conclusion however should not be considered final or static one. It may not be true when any significant change happen in one or more of the prevailing conditions.
3- The recommended application doses both of N and K may deviate, more or less, when the prices of both crop and fertilizer change considerally. This call for careful economic evaluation, taking into consideration the anticipated changes for inputs and outputs of potatoes production both in the national and international markets.