الفهرس 
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Abstract
This investigation was performed to assess impact of compost and compost tea on the availability of some nutrients, growth and yield of potato grown on sandy. For this purpose, a field experiment was established at Agric. Res. Station, Ismailia Governorate, Egypt during two successive fall (nili) seasons 2009/2010 and 2010/2011. Potato (Solanum tuberosum L.) Cv. Diamante was chosen for this study. The experiment was conducted under sprinkler irrigation system in split plot design with three replicates. The plot area was 17.5 m2 (3.5m x 5m). The main plots were devoted to application rates of compost tea without and with (400 l/fed). The sub plots were devoted to nitrogen fertilizers at rates of 25% of recommended N doses (37.5kg N/ fed) and 50% of recommended N doses (75 kg N/ fed). The sub-sub plots were assigned for compost at rates of 5 and 10 ton /fed. The obtained results could be summarized as follows Organic matter and total nitrogen were significantly affected by compost tea, compost and nitrogen fertilizers additions. Thus, foliar application of compost tea (400l/fed) or applying 50% of the recommended nitrogen fertilizers significantly heightened organic matter and total nitrogen in sandy soil. Also, corresponding increase was recorded through adding 10 ton compost/fed.
2. Addition of compost tea (400l/fed) and/or 50% of the recommended nitrogen fertilizers were more pronounced for increasing soil availability of N, P and K in both seasons. Also, the same results were obtained through applying 10 ton compost/fed. Concerning the interaction effect, applying compost tea combined with 50% of the recommended nitrogen fertilizers or applying compost tea along with 10 ton compost/fed achieved the best value of available nitrogen.
3. There marked increase in the available Fe, Zn, Mn and Cu by applying compost tea (400l/fed), 50% of recommended N fertilizers and 10 ton compost/fed on the studied sandy soil either alone or together. Regarding interaction effect, applying compost tea (400l/fed) along with 50% of the recommended nitrogen fertilizers maximized available Zn. But, the best value of available Mn was resulted in adding compost tea (400l/fed) combined with 10 ton compost/fed. The maximum values of Fe and Zn were achieved through applying 50% of the recommended nitrogen fertilizers doses combined with 10 ton compost/fed.
4. Foliar application with compost tea (400l/fed) maximized vegetative growth characteristics (plant height, number of main stems/plant and foliage fresh and dry weight) at 75 days after planting (DAP) versus without compost tea. Also, the highest values of studied vegetative growth were achieved as a result of raising nitrogen fertilizers doses from 25 to 50% of recommended. Similarly, the addition of 10 ton compost/fed gave the same obtained results as compared to apply 5 ton compost/fed.
5. Utilization of compost tea (400l/fed) decreased the weight of small diameters size tubers (< 35 mm).While, It was intensified weight of medium size (35-55 mm) and large (> 55 mm) tubers as well as total yield (Ton/fed), number of tubers/plant and Tubers yield (g/plant). Moreover, using 50% of recommended nitrogen dose or 10 ton compost/fed significantly heightened the yield and its components.
6. Concerning the interaction effect, applying compost tea (400l/fed) combined with 50% of recommended nitrogen dose gave the greatest values of number of tubers/plant, weigh of medium tuber size and total yield in both seasons. In this respect, adding compost tea along with 10 ton compost/fed gave more pronounced values of tubers yield (g/plant) and medium tuber size. Applied 50 % of the recommended nitrogen fertilizers combined with 10 ton compost/fed significantly affected medium tuber size alone.
7. The best values of dry matter, specific gravity, starch content and total carbohydrates were obtained by applying with compost tea (400l/fed) as well as 10 ton compost/fed. Similarly, high doses of nitrogen fertilizers (50%) caused a significant increment of these parameters. Regarding the interaction effect, applying compost tea (400l/fed) combined with 50% of the recommended nitrogen fertilizers gave the highest value of specific gravity. While, applied 50% of the recommended nitrogen fertilizers a long with 10 ton compost/fed maximized starch values.
8. Both applying compost tea (400l/fed) and 10 ton compost/fed achieved the lowest values of nitrate content. Increasing nitrogen fertilizers doses from 25 to 50% of recommended markedly heightened nitrate content. whereas, adding compost tea combined with 25 % of nitrogen fertilizers or 10 ton compost/fed along with 25 of nitrogen fertilizers significantly reduced nitrate content.
9. The maximum values of N, P and K contents in potato leaves and tubers were realized by applying either compost tea or 50% of the recommended nitrogen doses as well as 10 ton compost/fed.
10. Regarding the interaction effect, applying compost tea (400l/fed) combined with 50% of the recommended nitrogen doses gave the best values of N and P contents in potato Leaves as well as N content in tubers. Adding compost tea (400l/fed) along with 10 ton compost/fed achieved the highest values of N and P contents in potato leaves, while applying 50% of the recommended nitrogen doses combined with 10 ton compost/fed maximized N and P contents is potato leaves as well as N and K contents in tubers.
We conclude that soil application of compost and compost tea resulted in enhancing nutrient availability organic matter and total nitrogen. It also intensified all vegetative characteristics of potato yield and quality.
Furthermore, the obtained results ensure the importance of partial replacement of chemical nitrogen fertilizer by the use of the more safe and economical organic manures for potato plants grown under sandy soil conditions .In addition, its application would reduce the costs as well as decrease nitrate content in tubers.
We can recommend that applied compost tea (400l/fed) combined with 50% of the recommended nitrogen dose and 10 ton compost/fed maximized macro and micronutrients values in the studied sandy soil which reflected on N, P, K content in potato leaves and tubers as well as total carbohydrates and starch contents.