الفهرس 
Introduction
Effect of mineral nitrogen fertilizationOnly 14 pages are availabe for public view
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Abstract
This study was conducted during the two seasons of 2000 and 2001 in a private vineyard of Thompson seedless grapes located at Aboarsa village near Mansoura city, Dakahlia governorate, Egypt. The main objective of this investigation was to study the effect of using different levels of biofertilizers including Nfixing bacteria (Azotobacter chroococcum Azospirillum brasilense) and mineral nitrogenous fertilizers (Ammonium nitrate 33.5%, Ammonium sulfate 21.5%) on vegetative growth, cluster and berries physical and chemical characteristics and yield of Thompson seedless grape. NPK behaviour during different stages of grapevine growing season as well as dehydrogenase enzyme activity in the soil were also studied. Data obtained in this study could be summarized as follows: 1Leaves area/vine: Sixty N units gave the highest values of average leaf area in both seasons with significant differences. The highest level 9.9 g biofertilizer gave the highest values of average leaves area in 2000 and 2001 seasons. There were significant differences between all interactions, the interaction between 60 N units with 9.9 g biofertilizers gave the highest values followed by the interaction between 40 N units with 9.9 g biofertilizer during the two seasons of study. 2.Chlorophyll at full bloom: Adding different levels of mineral nitrogenous fertilizers had significant differences in total chlorophyll at full bloom. Sixty N units gave the highest values in both seasons. Leaves total chlorophyll were significantly increased with increasing biofertilizer rate from 0 to 9.9 g at full bloom. Vines treated with 9.9 biofertilizer gave the highest values for 2000 and 2001 seasons. All possible interactions between nitrogen and biofertilizer levels gave insignificant differences in both years of study. 3Yield: Adding 60 N units gave the highest values followed by 40 N units then 20 N units in 2000 and 2001 seasons with significant differences between treatments. Adding biofertilizers in high levels gave the highest values of yield, by increasing biofertilizer levels there was an increment in yield during both seasons. Adding nitrogen and biofertilizer in different levels gave insignificant differences. 4Cluster weight and volume: Adding different nitrogen levels had significant differences on cluster weight and volume in both seasons of study. Adding nitrogen at 60 units gave the highest values. As for biofertilizer in both seasons, increasing biofertilizer levels increased both cluster weight and volume. The highest values resulted from adding 9.9 g biofertilizer to the vines, all interactions had insignificant differences in both seasons of the study either for cluster weight or cluster volume. The treatment of 60 N units + 9.9 g biofertilizer gave the highest effect. Treatment 40 N units + 9.9 g biofertilizer gave also convincing values. 5Weight and volume of 100berry: Significant differences between values resulted from 60, 40 and 20 N units. Adding 60 N units gave the highest values, by increasing biofertilizer levels the values of both 100berry weight and volume significantly increased. Adding the highest level of biofertilizer gave the highest values in 2000 and 2001, insignificant differences resulted from combinations between mineral nitrogenous fertilizer and biofertilizer rates on both 100berry weight and volume in both seasons. Although the highest values were obtained from vines treated with 60 N units + 9.9 g biofertilizer for 100berry weight and volume, the treatment of 40 N unit + 9.9 g biofertilizer gave also convincing values. 6 100berry juice volume: Adding 60 N units gave the highest juice volume. While 20 N units gave the lowest juice volume in 2000 and 2001. By increasing biofertilizer level an increment in juice volume was observed, adding 9.9 g biofertilizer gave the highest values, treatments without biofertilization gave the lowest values. The differences between all interactions were insignificant, where treatment 60 N units + 9.9 g biofertilizer surpassed other treatments, and treatment 40 N units + 9.9 g biofertilizer gave suitable values. 7Firmness and adherence: Insignificant differences between both firmness and adherence values resulted from adding different levels of nitrogen fertilizer in both seasons of study, insignificant differences appeared between values of firmness and adherence during both seasons of study resulted from adding different biofertilizer levels. Insignificant differences for both firmness and adherence resulted from all possible combinations between different nitrogen and biofertilizer rates during the two years of study. 8Total soluble solids, acidity and TSS/acid ratio: Adding 60 N units gave in both seasons the highest total soluble solids percentage value, the lowest acidity values and higher TSS/acid ratio values. As for biofertilizer, increasing rate to 9.9 g gave the highest values for TSS, the lowest acidity values and highest TSS/acid ratio in both seasons. Interaction between adding 60 N units + 9.9 g biofertilizer gave the highest values of TSS %, the lowest acidity % and the highest TSS/acid ratio in both seasons. 9Total sugars: Significant differences in total sugars % resulted from adding different nitrogen levels. Sixty N units gave the highest values in both seasons. For biofertilizers, significant differences were observed. Since, adding the highest level gave the highest values of total sugars % in both seasons. Adding 60 N units + 9.9 g biofertilizer gave the highest total sugars % values in both seasons. These differences were insignificant at the first season, while it were significant at the second one. 10Nitrate content in berries juice: Adding different N units gave significant differences in nitrate concentration in berries. By decreasing nitrogen amount the nitrate content decreased in berry juice. Adding 20 nitrogen units gave the lowest values, Berry nitrate content decreased with increasing the level of biofertilizer. Since, adding 9.9 g of biofertilizer gave the lowest values. As for interaction treatments, adding 20 nitrogen units with 9.9 g biofertilizer gave the lowest nitrate content. 11 behaviour of NPK in leaves petioles during the growing season: In general, it could be concluded two opposite trend concerning N seasonal changes. The first trend was observed at the first stages of growing season till full bloom and characterized by gradual increase, and the second trend was from full bloom, which characterized with gradual decrease as the season advanced. Data also showed an obvious increase in P petioles content at the growing onset till full bloom and then decreased with the season advanced. Data for potassium concentration in petioles showed gradually decrease till harvest stage. 12Dehydrogenase activity: The interaction between 40 N units and 9.9 g of biofertilizer gave the highest value of dehydrogenase activity than the other interactions in 2000 and 2001 seasons. It is also clear that the first period (growth onset) in both seasons gave the highest values of dehydrogenase activity than other periods. According to the forcited results in the present investigation, it could be explained that nitrogen fertilizer applied to Thompson seedless grapevines at an adequate amount (60 or 40 N units per feddan) have a positive effect on growth (leaves area and chlorophyll contents), yield and most of physical and chemical characteristics measured on both clusters and berries. This effect was true except for berry firmness and adherence, which they were increased under low level of nitrogen. The obtained results also indicated that the applied biofertilizer at 9.9 gm biofertilizer had a benefit effect on vine growth and yield as well as most cluster and berry qualities. As for the interaction treatments of N and biofertilizer, the concerned results pointed to that 60 N unit + 9.9 gm biofertilizer was the best combination treatment. The vines under such treatment produced the highest yield/vine, and the resulted clusters recorded the highest weight and volume values. Furthermore, 100berry weight, volume and the berries juice volume of this interaction were higher than the others with respect to high TSS% and TSS/acid ratio along with low acidity. It also gave convincing effect on dehydrogenase activity. While, from the economic point of view treatment of 40 N unit + 9.9 g biofertilizer is the better because it recorded convincing values for all studied characters. In addition to the previous reported benefits, it reduced the amount of N applied. Such reduction decreased environmental pollution which is harmful for human, soil and water and produced healthy yield of a high demand for exportation beside minimized the cost of production and in turn increased the net income of vineyards. Therefore, such interaction treatment could be recommended in fertilizer regime of Thompson seedless orchards. In general, to reach the aims of this research (reduce mineral fertilizer amounts used in grape vineyard and produce healthy product), there are different conditions must put into consideration, these are: 1)?Determine actual N requirements of vineyards for expected economic yield taking into consideration soil and plant tissue analysis. 2)?Increasing fertilizer use efficiency throughout soil and crop management by applying fertilizer at the most suitable time (using element behaviour during growing season). 3)?Avoid conditions favorable to extensive N losses. 4)?Using biofertilizers as biological method to reduce elemental fertilizers used.