Spreading

The spreading is an agricultural technique consisting in spreading various products on fields of cultures.

These products can be chemicals like Herbicide S, or Pesticide S, or many chemical Engrais, of the natural products, like Excrément S animals.

Spreadings are ensured using specific material adapted to each type of Boue S and under solid and pasty products.

The slurry spreading, resulting from small Purification plant to average, is carried out using a ton with Lisier.

Spreading includes/understands:

  • the liquid die
  • the solid and pasty die
  • the die Composting

Technical specifications

The technical specifications applicable to spreadings on the agricultural grounds of muds resulting from the treatment of waste water are fixed by the decree of January 8th, 1998, signed by Dominique Voynet, then minister of environment.

Precise rules are fixed for the quality of muds of which:

  • of the rates maxima for the metal elements traces (ETM)
  • of the rates maxima for the Made up organic traces (CTO)
  • proof of harmlessness on the grounds
  • prohibition of spreading to less than 100 meters of the dwellings and to less than 35 meters of the wells, rivers or drillings.
  • prohibition of spreading on grounds softened or flooded
  • prohibition of spreading of the products of the type II on the cold grounds
  • limiting value of dry matter 3kg per square meter in 10 years or with 30 tons of dry matter per ha in 10 years.

Urban waste water treatment

In France in 2004, the urban waste water treatment generated more than 900.000 matter tonnes/an dries (50 grams of dry matter per day and) resulting from the Clarification sludge. Between 55 and 60% of them are épandues in agriculture, while 20 to 25% are put in discharge and 15 to 20% are incinerated. However because of the increase in population, of the growth of the park of the purification plants (step) and of the improvement of the output of purification, the production of waste products does not cease increasing, whereas the dies of Recyclage and elimination decrease.

Experimentation of spreading on wooded pieces

A possible alternative is spreading on wooded pieces. It would relate to mainly the forest settlements in intensive management (plantations of Résineux or Feuillus, Taillis for the production of Biomasse). Since 1998 these spreadings are carried out on an experimental basis and after prefectoral authorization within the framework of domestic network ERESFOR with the participation of ADEME.

The communal forest of Ychoux, to approximately 60 km of Bordeaux, in full forest landaise shelters one of the " sites-ateliers" studied by INRA. Maritime pines planted in 1992 emergent of an underwood of Heather S, Gorse S and Molinie blue. The researchers study since 1999 the effects in the medium and long term of regular spreadings of small quantities (3 tons of dry matter per hectare and per annum) of 4 types of muds (slurries, pasty, limed and perforated).

At the end of 3 years, they observe that with the slurries the growth of the trees increases by 16%. This growth is probably due to the improvement of the mineral nutrition, especially phosphated, highlighted by analyzing the pine needles. But the most spectacular effect is visible on the underwood, with an increase in biomass of 300% with the slurries, 150% with the compost.

For the two other types of muds, no significant result was still obtained.

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