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Abstract
1-INTRODUCTION
Sugar beet (Beta vulgaris, L.) is the second important sugar crop after sugarcane (Saccharium officinarium, L.). It is a vital crop to man as a source of high energy and as an important source of feed to livestock.
The important of this crop comes from its growing in the newly reclaimed land and giving a high sugar recovery, as well as its lower water requirement, compared with sugarcane. Moreover, sugar beet is specialized as a short duration crop, where its growth period is about half that of sugarcane .Also sugar beet being often, the most important cash crop in the rotation, it leaves the soil in good condition for the following cereal crop.
In Egypt sugar beet is grown as winter crop and harvested in spring and summer. Farmers sometimes, defoliate sugar beet plant as a source of animal feeding. The forced defoliation tested herein as a source of animal feeding was tested to distinguish the ability of the sugar beet crop to share in the overcoming of the forage crops deficient. On the other side leaves are important for photosynthesis, defoliate sugar beet may be impairs the growing plants and reduces root and sugar yield (Dunning and Winder 1972).
The trend in production of sugar plants differs between the types. Sugar beet area and production decreased during the last decade by almost 15%. The decline in beet area was partly compensated by an overall increase in beet yield of 17%. However, in order to achieve a higher yield, the plant has to absorb more nutrients. In other words, the demand for vertical increase in crop output can only be met by simultaneous increase in nutrient supply to the plants. As the tuber crops and sugar beet have a relatively poor root system when compared to cereals, this restrictive the soil volume, which can be exploited and thus requires a much higher nutrient elements concentration in soil solution to meet the demand for the crop
Nitrogen is considered to be the most important element of those supplied to sugar beet in fertilizer, as nitrate or ammonium, to provide maximum growth. Where the element is in short supply, yield is drastically reduced, and may even be halted in some soils. In Egypt, nitrogen fertilizer of sugar beet differ from site to another and the optimum rate of applied nitrogen for maximum root yield varied from 45 Kg N /fed to 120Kg N /fed ( Mahmoud et al ,1990 and Ramadan,1997) . The most remarkable effect of nitrogen fertilizer on sugar beet will be noticeably by improving the leaf canopy, on the other side, over use of nitrogen decreases both sugar percentage and juice quality.
Boron is an essential micro -nutrient for plants. Some plants are more susceptible to B deficiency and toxicity than others . Foliar of boron improved seed set, seed yield, and seed quality of Alfalfa (Dordas 2006). Boron as micro -nutrient is very important to have healthy plants and consequently, high root yield, and sugar content. Boron deficiency was the cause of heart rot and dry rot of sugar beet and B application plays an important role in carbohydrate and nitrogen metabolism water absorption and plant besides transpiration in and increasing the beneficial effect of potassium.
Therefore, the objectives of the present work were to study the effect of leaf