Digital Signal Processing Reference
In-Depth Information
enrichment of a water body is referred to as a eutrophication condition. Nitrogen, phosphorus, carbon
and, in some cases, silicon are the nutrients of most concern in relation to eutrophication. However,
because phosphorus is the most limiting nutrient in the fresh water environment, it attracts the most
attention in this case.
6.4.1.
Sources of nutrients in Lake Edko
Lakes, and shallow lakes in particular, are aquatic ecosystems often with an ecological structure which
consists of a great diversity of plant and animal life. This structure is finely balanced and the species
are inter-dependent. Birds and mammals rely for their food supply not only on the total productivity of
the species living in the lake but on the presence of a particular species, which in turn is subject to the
availability of nutrients. The microscopic algal communities, phytoplankton, are the first link in the
food chain for aquatic animals and fish. These and other floating plants acquire their nutrients directly
from the water, whereas the macrophytes that root into the lake bottom can obtain nutrients from the
sediments. These larger plants are crucial for the maintenance of the oxygen level in the water.
In the case of Edko Lake the situation is considered complicated because the lake receives drainage
water rich in fertilizers from the catchment in addition to unrecorded discharges from fish ponds.
Therefore, Agriculture is considered the largest source of nutrients into the lake water. This is due to
the excessive use of fertilizers rich in phosphorous and nitrogen compounds. Before we discuss the
analysis of the nutrients balance in Lake Edko it is important to give a summarized overview of the
fertilizers application and types used in Egypt.
6.4.2.
Fertilizers Types Used in Egypt
Agricultural land accounts for only 3.5 percent of the land area of Egypt. Two thirds of the agricultural
land is alluvial soil, fertilized for thousands of years by the Nile floods, and one third is land recovered
since the 1950s. Rainfall is minimal and almost all the agricultural land is irrigated. Soil salinity and
water logging are important problems in the reclaimed areas. Sprinkler irrigation and drip irrigation
are commonly used on the recovered area, and fertilizers are used on 13 percent of the land. There are
up to three harvests per year, the overall cropping intensity being 180 percent. Crop yields and rates of
fertilizer use are therefore relatively high.
The construction of the High Aswan Dam reduced the
quantity of suspended materials deposited on the soil during floods, which used to restore the fertility
of Egyptian soils for thousands of years.
Egypt has a long tradition of using mineral fertilizers; its first use of Chilean nitrates dated back to
1902. For over thirty years, all mineral fertilizers were imported, until the local production of
phosphate fertilizers started in 1936. The production of nitrogen fertilizers began in 1951. No potash
fertilizers are produced in Egypt due to the lack of resources, although it was reported recently that
some local potash deposits had been found (FAO, 2005). The demand for food and other agricultural
commodities is increasing in Egypt due to the increase in the population and improvements in living
standards. Efforts continue to improve crop productivity and quality. The breeding of new high
yielding varieties and the development of better agricultural practices are some of the measures aimed
at increasing agricultural production to meet the increase in demand.
Appropriate fertilization is one of the most important agricultural practices for achieving the objectives
on production. Evaluation of the best source of nutrients, optimum rates of fertilization, suitable
timing and proper fertilizer placement are necessary for efficient fertilizer management. In Egypt,
there are several traditional practices that are commonly implemented and which play a major role in
restoring and maintaining soil fertility. Among these practices are:
Planting berseem clover as a winter fodder crop before the cotton crop, which provides a
green manure that is ploughed in after taking one or two cuts.
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