Use of manure as organic amendment

The use of these manure as fertilizer is the most widely used solution, require low-cost investment and provide economic benefits, whereas the high prices of inorganic fertilizers. However, there are limitations to its use on the storage, transport and application of large quantities refers.

Taking into account the volume of waste water generated in the region of Murcia, and the total arable and considering the existing legislation, RD 261/1996, which allows a maximum of 170 kg of N application / has and year, in declared areas vulnerable, it is estimated that half the arable area dedicated to irrigation would be required for the implementation of the waste water generated in the region in a year,.

Thus confirms the need to develop a system of management of waste water that is beneficial to ranchers and farmers, allowing the withdrawal of surplus farming and its recovery controlled as fertiliser on agricultural soils, in a sustainable manner for the environment. Why is has created a system for reuse of waste water after its recovery, so that farmers whose farmland for the manure as fertilizer, with farmers, whose farms are coming and which transferred their manure for such use have been in contact.

The study focuses on the area of the Valley of Guadalentín, because it focuses 50% of the pig farms in the region of Murcia. For their development, counts on the participation of farmers (A) and (G) farmers whose holdings are located near each other, estimating a radio average less than 5 km away.

The taking of samples of waste water, is done in triplicate, in each participating swine farm ponds. Subsequently, analyses the slurry of each farm, in order to characterize them and establish the dose of application. In the same way, is also a sampling of soil of the farms in which is intended to apply the manure so that samples are collected both surface (0-30 cm), and depth (30-60 cm). At the same time, are taking samples of soil in areas white, or points that will not make application, to have them as a reference. All production and reception areas of the slurry, are visited and georeferenced using GIS (GIS) and Global geo-positioning (GPS) systems.

Samples of soil and waste water are processed in the laboratory for further analysis and physicochemical characterisation, before and after the application, using standard methods. Application doses are established, mainly based on the data content of N (method described by Duchafour, 1970), following the guidelines established by the legislation (RD 261/1996 and RD 324/2000). The system of distribution of slurry chosen, because of the economic advantages and availability of machinery, is tanks prepared with the right proportion of waste water. The application is done with dispersers fan, by way of irrigation in cover, at the beginning of the crop cycle. Soil samples also includes analysis of textural class (the Robinson pipette method).

According to Dr 324/2000 farming that seek to use the manure as fertilizer mineral body, must comply with certain requirements: as it is prove to the competent body of the autonomous community, which have sufficient agricultural areaown or concerted, for the use of the manure as fertilizer, so that in vulnerable areas may not exceed the amount and 170 kg of N/has/year (Dr 261/1996) calculated this dose from the indications in annex I of the RD 324/2000. For areas not vulnerable legislation allows implementation of up to 210 kg N/has/year. In this study, it has established itself as maximum dose (table 1) specified for vulnerable areas in order to not exceed the capacity of the soil.

The data obtained allow noted that the content of N is always superior in surface (S) to in depth (P) (Figure 1). Similarly, can be seen in the first year of study, the difference in content of N application areas and the white areas (without application of manure) is not statistically significant (Figure 1), so that we can say that there is a cumulative effect of N by the application of liquid manure.

Here it follows the importance of the treated soil textural class, when the texture is more clayey and compact soils have a low permeability and give rise to low ratios of decomposition; Thus the application of waste water in these soils can be beneficial due to the high retention of nutrients for the same capacity.

As you can see in the data presented in table 2, on the farms in study the predominant textural class is the clay, which is soil that accept this type of application. However, must be in mind the content of other nutrients (P, (c), heavy metals) also considered in this study, both waste water and the soil, to optimize these applications in the long term.