WATER AND NUTRIENTS MASS BALANCE OF CATCHMENT - LAKE SYSTEM - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 126

Figure (6-2): Estimates of the areas and fertilizer requirements of “new” and “old”
land up to 2017 (Source: MALR, 2003)
Efforts are being made to increase the composting of agricultural residues as a source of plant
nutrients, in order to contribute to the improvement of the physical properties of the soil and the
protection of the environment. According to the FAO report, 2005, mineral fertilizers, especially
nitrogen, phosphate and potash are being applied to an increasing extent in Egypt. Figure (6-3) shows
that the consumption of nitrogen and phosphate fertilizers has tripled during the last 30 years.
Figure (6-3): Consumption of nitrogen and phosphate fertilizers during the last 30 years (Source: Taha, 2000)
The input of nutrients from different sources, such as soil, air, water and other sources, including
organic manures, should be equal to the amount removed or taken up by the crop. If the quantities
from these sources are not sufficient for the crop to reach the target yield, the difference should be
added as fertilizer. Insufficient amounts of nutrients result in a, loss of yield. Excessive amounts
represent a waste of resources, possibly a decrease of yield and could be an environmental hazard, as
identified in the case of nitrogen (Fawzi, 1992).
From the information given above on the use of fertilizers in Egypt, it is obvious that a huge amount of
fertilizer is drained to the surface waters as a residual from its application. Most studies carried out to
evaluate different sources of phosphate have focused on the direct effect of these sources. Very little
work has been done on evaluating the residual effect of these sources by means of long-term
experiments. The fertilizing value of various sources of phosphate should include both the direct and
the residual effects of the different sources under different cropping systems. Because nitrogen
fertilizers are the most used fertilizers in Egypt, studies should focus on the rate of nitrogen fertilizers
applied to the main crops, using different sources of nitrogen, time and method of application, in order
to increase the efficiency of the fertilizers and to reduce nitrogen losses (Hamissa, 2000) to surface
waters.