Impact on the soil by a outdoor pig production system in the long term

UNIVERSITY OF THE REPUBLIC OF URUGUAY. Faculty of Science.

Thesis for the title of Master in Environmental Sciences 

  

Author: SANTIAGO MONTEVERDE; Tutor:  AMABELIA DEL PINO , co-tutor:  DANIEL PANARIO

ABSTRACT 

In recent years there has been increased interest and organic production of pigs in outdoor systems, considered by several authors as an alternative to large confined systems, being friendly and environmentally friendly animal behavior. However, some major conflicts may appear in how and to what extent the different objectives productive and sustainable resource management can be combined. With the aim of studying the impacts on soil by pig farming system developed in Pig Production Unit (CRS, Faculty of Agriculture) after 12 years of installed, sampled 6 plots of 1500 m2 and compared with a control soil (without pigs). The soil is a Brunosol and animals are handled in plots averaging 6 sows ha-1 yr-1, balanced rations supplied to them daily and permanent access to pasture and alfalfa or clover mixture of red, white and chicory, all production stages performed under field conditions. The first stage was determined on the floor of the control area and 6 plots (in grid 5x5 m) penetration resistance (PR) to 46 cm depth. Followed by sampling at 4 sites in the same grid surface (0-15 cm) for determining organic carbon, phosphorus Bray 1, N-NO3, N-NH4, pH, electric conductivity (EC). This information is used to construct the maps of impacts and identify limits related to the management zones. The last stage of sampling included the control area and the 6 plots at two depths 0-15 and 15-30 cm. Each plot was divided into 3 different areas of management: (i) service without planted pasture (drinkers, feeders and shelters), (ii) service with planted pasture, (III) with planted pasture typically "grazing" (75% of the area). Was determined bulk density, RP, organic carbon, carbon and phosphorus in the fraction of the organic matter (OM) 200-2000 microns and 50-200 microns, carbon in MO less 50 microns (MONP), K, Na, Mg, Ca, Zn and Cu (Mechlich III), phosphorus Bray 1, phosphorus in solution, N-NO3, N-NH4, pH, EC, microbial respiration and nitrogen mineralization potential.

The system produced significant changes in physical, chemical and biological properties of soil, creating spatial heterogeneity in different areas of management. Concentrated service area and the major impacts of grazing (75% of the area) children. The system caused soil compaction throughout the area, exceeding 2 MPa of PR only very small areas of Zone I, which was the most packed. The MO was reduced from 4.7% down to 3.9% seen in the pigs in the soil surface layer, also 17% decrease in depth, due mainly to decreased MONP without significant differences between zones of the plots. It increased the content of P, NO3 and K mainly in the service area (reaching an average of 152 mg kg-1 of P Bray and 3.66 mg kg-1 of P in solution in the area I), correlated to the Zone I to increased EC, which values ​​did not problematic. Excess N was scarcely accumulated in the ground, increasing the risk of water contamination. In the grazing area decreased 0.4 pH units than the control, which did not differ significantly in the service area. Some impacts spread significantly at 15-30 cm layer (PR, COS, P,  EC and NH4). No problems were observed accumulation of heavy metals (Zn and Cu).

The results suggest that pigs produce field can be an alternative to confined systems, but is an activity with great potential to generate environmental problems by inadequate management practices.

Keywords: outdoor pigs, environmental, soil compaction heavy metals, nutrients, particulate organic matter.


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