Monday, 5 July 2010

Life in a Nitrate Vulnerable Zone

The Ministry for Resources and Rural Affairs (MRRA) recently published the Consultation Document on the second Nitrates Action Programme for Malta. The MRRA asked for NGOs and other stakeholders to review this document and to pass on any recommendations to the ministry - Greenhouse has discussed the changes in the Action Programme and passed them on to the Ministry. Before delving into the details of the Action Programme and the recommendations brought forward by the Greenhouse team, letʼs look into what nitrate pollution is and why people in Malta should care about a Nitrates Action Programme, in the first place.

The main concerns regarding Nitrate Pollution involve the contamination of water by large concentrations of nitrates. There are three main reservoirs which are typically polluted by nitrates. The first two are the marine environment and inland freshwater habitats, where an excess of nitrate leads to algal blooms and c resulting in a potentially catastrophic changes in the biodiversity of the habitats. [1] Now this might be alarming enough but the effects of nitrate pollution on groundwater supplies are far more frightening for the man in the street who may not care so much for fragile marine ecosystems. High concentrations of nitrates in drinking water can lead to methemoglobinemi and gastric and intestinal cancer [2]; considering Malta gets around half of itʼs drinking water from groundwater sources [3], it is quite important that we protect these sources from nitrate pollution.

The recommended maximum of nitrates in groundwater, set by the EUʼs Nitrates Directive is at 50mg/L [3,4], however out of Maltaʼs 15 Groundwater bodies (GWBs) 11 are above the limit (8 of them are over double the limit). It is worth mentioning that out of the four bodies not over the limit, one is only 0.6mg/L short of the limit, while the concentration for another body (the Marfa GWB) has not been calculated yet and is expected to be above the limit. So really, only two ground water bodies can be considered to be not polluted by nitrates.[3] This is all outlined in detail within the second section of the Action Programme.

In 2008, the MRRA commissioned a study to determine the source of nitrates in Maltaʼs Groundwater bodies, which was carried out by the British Geological Survey (BGS). This interesting study, involving isotopic signatures of oxygen and nitrogen found that most of the nitrates found in GWBs originate from cultivated areas and also from manure dumps. [5] It has long been supposed that agricultural practices were the cause for nitrate pollution of local water bodies, in fact the whole scope of the first Nitrates Action Programme started in 2004 was based on agricultural management practices and the setting up of the Code of Good Agricultural Practice (CoGAP) (another major aim of the action programme was to set up rugged monitoring schemes to ensure scientific data is available).

As the main document suggests Malta has a massive problem with nitrate pollution, especially in our Groundwater bodies, which has no doubt been caused by poor agricultural practices (using too much fertiliser, illegal dumping or poor storage of manure, etc). Here are the solutions (in summary) as put forward by the MRRA, built on the original Nitrates Action Programme (2004) with some practical amendments:

  • Application of fertiliser (both organic and inorganic) is prohibited between 15th October and 15th March.
  • Application of fertiliser is prohibited on land which is close to watercourses or where the soil condition or slope suggests that there is a significant risk of the fertiliser being swept away by runoff.
  • Application of slurry is prohibited
  • Application of fertilisers is prohibited within a 5m radius of fresh watercourses of any kind and 50m from a borehole in use for public water supply.
  • Application of fertilisers shall be based on fertilisation planning taking into consideration the balance between the foreseeable nitrogen requirements of the crops and the nitrogen supply to the crops from the soil, water and from fertilisation.
  • Inorganic and organic fertilisers shall be applied close to sowing and splitting of fertiliser application is recommended whenever possible.
  • The amount of “total nitrogen” applied from livestock manure, including excreta by animals themselves, shall not exceed 170 kg N/ha per year.
  • The capacity of storage facilities for livestock manure of a holding shall be sufficient and adequate to provide for the storage of all the livestock manure which is likely to require storage between the 15th October to 15th of March.
  • Manure shall be stored in a leak-proof, covered storage clamp which is connected to a cesspit. The Cesspits must be leak-proof, covered and must be sufficient to collect all urine and washings for at least 15 days (both cesspits and manure clamps must be certified by a warranted architect).
  • Crop rotation shall be practised where necessary.
  • Farm holdings with an area >1 ha and under intensive irrigated cultivation shall have a Nutrient Management Plan.
  • Users of organic and/or inorganic fertilisers shall be registered with the competent authority responsible for nitrates.
  • Users of organic or inorganic fertilisers shall be required to attend a compulsory course on the use of fertilisers.
  • All sales and purchases of organic and inorganic fertilisers shall be notified to the competent authority responsible for Nitrates.
  • All importers, distributors and resellers of fertilisers shall be registered with the competent authority.

Greenhouse gave five recommendations for the ministry to consider:

  1. The banning of ammonium nitrate fertilisers; ammonium nitrate is very soluble and is often washed away before the crops can absorb it leading to a high degree of nitrate pollution.
  2. Encouraging the use of Slow-release fertilisers, such as methylene urea, which are less susceptible to being washed away and into the water table.
  3. Encouraging and providing incentives for proper crop management with crop rotation utilising leguminous plants to provide natural sources of nitrates.
  4. The removal of the point banning fertiliser application during the rainy season; although this ban would be beneficial it is most probably quite impractical especially since farmers could apply an excess of fertiliser prior to the ban, causing just as much damage. We are inclined to believe that such a ban would result in an unnecessary burden on the farmer.
  5. Awareness on the damage of excess-irrigation and monitoring the water consumption for irrigation could help reduce nitrate pollution by slowing down the rate at which fertiliser dissolves. Metering and other enforcement measures could be used along with educational campaigns.

It was found, by the BGS, that the time that water spends in the aquifer in Malta is very long (15-40 years in Malta and 25-60 years in Gozo) which, when coupled with the long time it takes for nitrates to reach the water table, means that even if even all nitrate-producing activities could be stopped tomorrow, it would take decades to flush out nitrate to an acceptable level.[Stuart, Marianne (BGS). Going Underground. Planet Earth (Summer 2009) - National Environment Research Group (UK)]
In other words, we will be living in a Nitrate Vulnerable Zone for many years to come.

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