Irrigation sources

Trial sites must be selected on the basis of uniformity (soil characteristics, areas of sunshine, etc.), and areas that are susceptible to erosion or areas where drift of chemicals from neighboring fields might occur should be avoided. Irrigation sources are supplied, preferably nearby. 

Hutchison, M. L., Avery, S. M., and Monaghan, J. M. (2008). The air-borne distribution of zoonotic agents from livestock waste spreading and microbiological risk to fresh produce from contaminated irrigation sources. ]. Appl. Microbiol. 105, 848-857. 

It is also a known fact that leaching of saline soils making about 60% of the cultivated lands requires 4,000-5,000 m of water, on the average. Assuming transit water losses from irrigation sources to the field being 30% of the withdrawn water, then the actual water use exceeds twice the needed quantity of water. The result of such practices was a drastic distortion of the environmental equilibrium on irrigated lands. 

With a growing scarcity of freshwater available for irrigation, other sources of lower quality like brackish water, saline water, and treated wastewater become more important as additional or substituting inputs for the agricultural sector. At the same time, it is clear that a sophisticated treatment like desalination or nanofiltration under current conditions is still far too expensive to be a major solution to future irrigation water needs. Hence adaptation of farming and irrigation practices to the particular water qualities constitutes a more viable approach. 

These results underline the necessity of establishing regional water quality criteria when planning the use of saline water sources for irrigation. These criteria are of primary importance for establishing suitable strategies for the safe use of saline aquifers in Syria and other arid and semi-arid regions. 

According to the NRI study [15], the Nile is the main source of drinking water in Egypt. Over 85% of the country s water is consumed annually by irrigation. Hence, safe water will provide pollutant-free agricultural products and production will increase as well. The concentration of organic material decreased 15-69% in the main course, dissolved salts decreased 1.5-2.0%, while phosphate concentration decreased 14%. The total water quality was improved by an average of 14%. The... 

Fig. 1 Results from a redundancy analysis of stream nutrient concentrations vs. catchment characteristics in 31 headwater catchments in Catalonia (Spain). Note how phosphorus (SRP) and ammonium (NH4) appear associated with urban point and diffuse sources (Urban percent urban land use, Inhabs number of inhabitants, eq. inhab inhabitant equivalents), whereas nitrate (NO3) concentration is positively associated with irrigated agriculture (IrrAg) and bovine cattle units (ECU), and negatively with mean catchment slope (slope) and percent forest land (Forest). The other variables are Area log area, P precipitation, NonIrrAg non irrigated agriculture. Data are from the Catalan water agency (http //ww.gencat.cat/ac)...

Another groundwater contaminant that can be removed by reduction reactions is perchlorate. Ammonium perchlorate is a solid rocket fuel, and wastes from its manufacturing have contaminated some irrigation and drinking water sources, among them the lower Colorado River in the American Southwest. Elevated perchlorate levels have been linked to human health effects, and because perchlorate has been found in vegetable crops such as lettuce, there is concern that this contamination could have serious consequences. 

Another important test location factor is the availability of water for irrigation and for preparation of the spray solution. The use of culinary water sources (either private or public water sources intended for human consumption) or groundwater (from wells) is usually less problematic than using water from surface sources (rivers, lakes, or canals). If surface water is used for the study, care must be taken to ensure that farm production activities upstream from the plot area have not contaminated the water supply with pesticides that could contaminate the plot area. Careful site selection will help avoid problems from the water available at the site. 

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