MAP Technical Reports Series No. 106 UNEP

10.1 Elimination of nutrients at source
10.1.1 Agriculture and livestock
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Measures that can be taken in agriculture to reduce the burden of nutrients (nitrogen
compounds in particular) are preventive in character, and concerned foremost with the rational
use of fertilizers. In essence, kind and amounts of fertilization should be reconciled with and
proportioned to the nature of the soil and the nutritional requirement of the crops to be cultivated.
A rational approach in this regard will not only reduce losses of useful fertilizer simply being
washed away due to surplus amounts used, but also bring considerable economic benefits to
farmers by saving on unnecessary consumption. Another important avenue of improvement that
might be pursued is the adoption of "slow release" synthetic fertilizers.
Also, irrigation systems should be improved in order to minimize losses by wash-out
and erosion. Erosional losses can also be minimized by various methods of strip farming, like
protective strips of grassland around crop land; alternation and systematic rotation of crop types
in adjacent strips; etc. Particularly important in hilly regions is ploughing and cultivation across
to, not with the slops of terrains.
Radically different from simple fertilizer and soil control is the option of selecting
"genetically improved" crops having a greater capacity for assimilation and accumulation of
nutrients (which will therefore be taken up from the soil more rapidly and efficiently), or having
a lower requirement in respect of certain nutrients (allowing a reduction in the use of fertilizers).
In the area of livestock husbandry, action can be taken both to treat sewage and to
encourage manure-spreading. Sewage purification by appropriate treatment is possible in
theory, but costly, and often impracticable because of lacking technical know-how by rangers
regarding the running of treatment plants. Spreading is easier, and widely practised. Whilst the
manuring of agricultural land is certainly beneficial, in view of the fertilizing and organic
substances that are added to the soil, local and regional development authorities must take care
nonetheless to avoid excessive concentrations of livestock in a given territory, preferably at the
planning stage, since extensive spreading may carry the risk of contaminants washing into
surface waters and percolating down to the aquifers, and in case of continued excessive
spreading to damage soils.
10.1.2 Detergents
Utilized as a tripolyphosphate in detergents, phosphorus has the advantage of being
a relatively cheap additive for enhancing the capacity of a washing product to remove dirt;
conversely, it has caused serious problems in aquatic ecosystems, and indeed continues to do
so. Many researchers from the 'fifties onwards have shown how instances of eutrophication
began to increase in number as the use of such washing products became widespread. On the
prevention front, polyphosphate elimination at source can be achieved by adopting alternative
substances which perform the same function. Polyphosphate reduction and substitution has
already been effected in many countries, with the introduction of new zeolite formulations
containing salts of nitrilotriacetic acid (NTA) or citrates.
10.1.3 Industry
The preferred action is without doubt to adopt production cycles which reduce or
prevent the formation of nutrient-rich liquid waste. At all events, the industrial processes