Pollution produced by nitrates from agricultural sources

Nitrogen fertilization with mineral fertilizers is recommended for all crops except legumes, in which 10 to 20 kilos of nitrogen per hectare must be provided.

Inclined and steep terrain: 

• Make the application of fertilizers in such a way that runoff does not occur.
• Maintain certain drains, hedges and embankments with grass, as well as the bottoms of slopes.
• Do not use high pressure spray guns (greater than 3 bars at the sprinkler) for liquid fertilizers. 

Land near watercourses:

• Leave a strip between 2 and 10 meters wide without paying, next to all water courses. Fertigation systems will work in such a way that there is no dripping or spraying less than 2 to 10 meters away from a water course, or that drift can reach it.
• Do not apply within 35-50 meters of a source, well or borehole that supplies water for human consumption or is to be used in milking parlours. 
• Keep the banks or margins with grass.
• Preserve trees, hedges and wooded areas on the banks of rivers and streams.
• Apply chemical fertilizers and manure to control nutrient losses to the water.

All farms must establish fertilizer plans for each plot and have a fertilizer application log book. It will specify the nature of the crops, the application dates, the volumes and amounts of nitrogen used from any source (manure, sludge, garbage or compost produced or introduced on the farm, purchased nitrogenous fertilizers, etc.). 

• Blanket irrigation and deep percolation should be carried out in clay soils for crops with a deep root system.
• Lateral (furrow) infiltration irrigation should be applied in deep, expansive, low-permeability clay soils and in crops with deep roots.
• In sprinkler irrigation, the distribution of the sprinklers and the interference of the wind must be taken into account.
• Fertigation, the fertilizer should not be put in the water from the beginning of the irrigation, but preferably after having supplied about 20-25% of the volume of water; fertigation should be completed when 100-80% of the water volume has been supplied.
• Drip irrigation, periodically vary the flow rates and irrigation times.

• Improve the order of succession of crops in such a way that the surface of bare soil is reduced during periods that present risks of washing.
• Bury crop residues, since the increasing amounts left by well-fertilized crops have proven to be soil improvers and provide it with greater water retention power, thus reducing soil erosion.
• Protect the fallow land from erosion by seeding it with legumes.
• Quickly implant a nitrogen-demanding crop after a legume.
• Combine cultural techniques (plowing perpendicular to the slope, intermediate crops) and improvement techniques (hedgerows, slopes and turfed drains).

• Keep all waiting and exercise areas, especially outdoor areas, accessible to animals and all evacuation or storage facilities for livestock effluents impermeable.
• The slope of the floors of the facilities where the animals remain must allow the evacuation of the effluents. The latter will be evacuated to storage containers.
• Collect the cleaning water in a sealed network and direct it to the effluent storage or treatment facilities.
• Store solid excrements in a sealed surface with a low point, so that the runoff liquids are collected and evacuated to storage or effluent treatment facilities.
• Have at least enough storage capacity to cover the periods when distribution is not advisable.
• Separately collect rainwater from roofs and evacuate it directly into the natural environment.