Fertilizer application and livestock waste/
manure are the primary sources of P in agricultural/
pastoral catchments [4–6]. Application of P in
excess of plant requirements leads to buildup of
P and saturation of soil sorption sites. Therefore,
there is a greater potential for P desorption into
soil solution and loss by transport mechanisms
such as leaching and surface runoff [7,8]. In
Norwegian surface waters, 45% of the anthropogenic
P inputs originate from agricultural areas.
Agricultural areas contribute to 61% of P in the
Chesapeake Bay in USA [9]. As a result, agricultural
practices can be significant in the enrichment
of water bodies with P. This may be critical
for eutrophication control in lakes since most of
them are P limited.
Lake Uluabat is one of the shallow lakes
under stress in Turkey. It is located in between
40°12’N latitude and 28°40’E longitude in Bursa
Province [10]. Lake surface was reported to be
116 km2
in 1998 [11]. Lake Uluabat had been
considered as a potential potable water source
through 1970s. However, since 1990s, its water
quality has deteriorated. Occasional fish deaths
have been observed because of the dissolved
oxygen deficiency resulting from wastewater
discharges and drainage waters coming from
agricultural lands, and/or increase in algal population
[12]. Decrease in biodiversity has been
experienced in recent years due to water quality
problems [13]. Due to its ecological significance,
the lake and its surrounding area, together with
the protected habitats, were included in the
RAMSAR Agreement on April 15, 1998. As a
result, protection of the natural structure and
ecological character of Lake Uluabat is undertaken
internationally [12,14].
In a study conducted by the General Directorate
of State Hydraulic Works (SHW), P was
determined as the limiting nutrient in Lake
Uluabat [14]. Through 1986–1990, the maximum
orthophosphate concentration had been
0.25 ppm. However, as a result of activities in
the region, P loading to the lake has increased