Effect of nitrogen application doses and spraying urea, GA3 and naa on flowering, fruit set and fruit drop percentages of washington navel orange trees
2011
Ibrahim, M.M. | Al-Ashkar, R.A. | Tawfik, A.A. | Abdalla, K.M.
The effect of GA3, NAA and urea as well as the time of N application (Feb., May and August) three doses or (early Dec., Feb., May and August) four doses were studied on fruit set, fruit drop and fruit retention percentages. Fifteen-years-old Washington navel orange trees grown in a private citrus orchard at Minia El-Kamh, Sharkia Governorate, Egypt during three seasons 2008, 2009 and 2010 were used for this study. Spraying GA3 three times a year at 10 ppm (beginning of flowering, full bloom and fruit set), four N applications (early Dec., Feb., May and August) and their interactions gave the maximum fruit set, fruit retention percentages and reduced total drop percentage. Four N applications reduced June drop and primary fruitletss drop percentages, but primary fruitlets and June fruit drop percentages were higher under GA3 spraying treatments. Earliness of flowering in spring was affected by some factors; i.e., N fertilization, temperature and water stress. Nitrogen application four times/ year gave early flowering (about one week earlier). However, the interaction between four doses and urea sprays at 2 %three times a year gained similar results.
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