A laboratorial study was accomplished to explore the effect of using fish discharged water in irrigation on soil productivity. Oreochromis niloticus and Claris gariepinus were used in the study for fish culture, and Trigonella foenum-graecum, Trifolium alexandrium and Vicia faba were used for the agriculture application. Germination percentage, total N, P and K in plants and soil were determined. Seeds were planted in the same soil into four groups and subjected to four irrigation treatments; irrigation with the supplying water of fish culture (T1), the drainage water of tilapia (T2), the drainage water of catfish (T3), and the drainage water of catfish reared on tilapia drainage water of (T4). Results indicated that soil content of OM% and NH3 changed significantly (P<0.05) with the change of treatment and the planted species. A higher productivity was found in T2, T3 and T4 compared to T1, the highest was found in T4 than other treatments. The application of integrated fish culture and agriculture methodology in areas where low fertile soil prevails was recommended.
Keywords: Soil germination; Food security; Freshwater fish; Water recycling
Poor soil quality is one of the major problems against spreading green areas and obtaining higher productivity for food security. Assessment of the State of the world’s soil resources from based on observations made in the 1980s shows a dramatic degradation of soil all over the world . Irrigation was found to be one of the important factors to reduce soil fertility as it is able to remove several soluble beneficial salts from root zone . The use of waste water in irrigation can result in deleterious effects on soil, humans and the environment as well leading to various changes in the physicochemical and microbiological parameters of the soil, causing accumulation of chemical and biological contaminants in soil which may lead to serious health problems in humans .
Many soil improvement approaches have been applied to overcome soil problems; organic matter application to such soils can result in increased water-holding capacity and fertility  to obtain higher soil productivity. Bacterial de-nitrification for precipitating carbonate , manure additives  were found successful as well. Cultivation of cotton in the rotation was also successful as an entry point of nutrients via fertilization to increase soil productivity of the crops .
Also, CO2 application in soil was found able to significantly increase total root production of crops planted in infertile soil,however, it couldn’t cause similar effect when applied in fertile soil . Drainage water of fish culture was evidenced to be highly enriched with natural fertilizers  due to fish excrete which contains high content of ammonia and urea and organic matter. Recycling such water in fish farming of appropriate different fish species resulted in accumulation of these contents  and led to soil quality increase when irrigated by this recycled water.
Thus, in this research, the productivity of soil to cultivate different types of plants species was investigated; irrigation with the recycled water of fish framing was applied to verify the efficiency of such integrative methodology to provide production of crops and fish in parallel.
Tilapia (Oreochromis niloticus) and catfish (Claris gariepinus) were reared in different aquaria, and other aquaria for catfish were reared in the drainage water of tilapia aquaria as described by . Seeds of fenugreek (Trigonella foenum-graecum), clover (Trifolium alexandrium), and faba beans (Vicia faba) were brought from seeds market. The seeds were planted in four separate groups in similar soil.
The groups were subjected to four irrigation treatments for 12 weeks; The first group was irrigated with the water used as a supplying water for the fish aquaria (T1), the 2nd group was
irrigated with drainage water of tilapia (T2), the 3rd group was
irrigated with the drainage water of catfish (T3), and the 4th
group was irrigated with the drainage water of catfish which was
reared in the recycled drainage water of tilapia (T4). At the end
of the interval, determination of E.C. and total organic matter
OM%  were made to soil, while total NH3 , total N, and
P  and total  were made to soil and plants. Data were
tested by SPSS 13.0, 2004 multivariate ANOVA (Wilks’ Lambda)
and LSD at (P<0.05).
Generally, results indicated a significant difference between
soil contents and germination in T1 and in T2, T3 and T4. A
significant interaction between tested parameters and between
species in their response towards the change of treatment was
Germination was relatively higher in T2, T3 and T4 compared
to T1 in all planted species; germination of fenugreek was higher
in T2, T3, and T4 by 40, 38.3 and 48.3% respectively, and 46.2,
48.1, 63.5% for clover respectively, and 37.04, 42.59, 61.11% for
faba respectively. However, all species in T4 showed the higher
germination (Figure 1).
Soil analysis revealed a significant change in soil parameters
in T2, T3, T4 compared with T1 as shown in (Figure 2) the change
varied from a species to the other, this variation was significantly affected by the type of each planted species; where OM%, total
NH3, and total N were significantly increased in all species.
However, all parameters were the highest in T4. Meanwhile, no
significant difference was found between groups in soil salinity.
Germination rates suggested that the type of irrigation water
influenced the germination process and that it mostly provided
the soil with acceptable amounts of nutrients needed for growth.
But, sensitivity to salinity, storing conditions, water requirements
and/or time of plantation, drought and temperature might all
interfere to cause these differences . However, all these
factors should be considered and observed by agriculturists
when the system is applied on the real ground.
Total N content was highest in soils planted with Vicia faba
in all groups which is mostly due to the Rhizobium bacteria
(Phizobium leguminosarum) on its roots which perform
enormous Nitrogen fixation in the soil ; the variation of
water sources in treatments supported the increase of N content
in the used irrigation water . Field studies conducted by
Sparrow showed that faba bean had the highest N2 fixation
rates of all the legume species tested, highest N accumulation,
and high total plant N concentration at final harvest. Total NH3
was obviously increased by the treatment which was enriched
with NH3 as evidenced by . Meanwhile, total K content was
probably reduced in soils sue to the crops consumption. Yet,
the level is below medium levels (60 - 120 ppm) as reported by
Recycling water in fish culture then in irrigation is not only
a method to save water, but it can also be as a source of organic
fertilizer to low fertile soils to provide a higher productivity
of crops in addition to fish production. It is recommended to
field test the experiment to improve the quality of low fertile
soils in arid areas to facilitate its cultivation, and to increase its
field capacity to protect it from degradation. These outcomes
may strongly encourage promoting the living standard of the
inhabitants in these areas and provide them with food security
of plant and animal proteins.