28 sept. 2012

Spatial variability in soil chemical properties in a outdoor pig production system.

Autores: Santiago MONTEVERDE, Amabelia DEL PINO, José PIAGIO
En: 19 th ISTRO Conference 2012- (International Soil Tillage Research Organization) Montevideo, Uruguay.


Outdoor swine production may be an alternative to animal welfare problems, pollution and biosecurity of confined systems. But some management practices can modify the spatial variability of soil chemical attributes and sometimes produce environmental problems. The aim of this work was to study the spatial variability of chemical characteristics in a Brunosol (Canelones, Uruguay), after 12 years of a pig farm installed in the field and compared with a control soil (without pigs). Soil samples were collected from surface (0-15 cm) in a control area and 6 plots (1500 m2 each), with 3 different areas of management per plot (n = 24). The selected areas were: service (drinkers, feeders and shelters), distant grazing area, and intermediate area. Complementary sampling was made in a grid (5x5 m) in 4 of these plots. The chemical attributes of the soils studied were: organic carbon (SOC), NO3-N, NH4-N, P (Bray) and in solution, pH and electrical conductivity (EC). The comparison o f variables between soil with and without pigs, the difference between areas within the latter was made statistically by ANOVA or Kruskal-Wallis nonparametric test and through geostatistical tools maps were built using interpolation splines. In the service area increased statistically in relation to the control the concentration of nitrate-N, available P and in solution, and the EC, however NH4 and SOC decreased. In the grazing area only available P increased relative to the control, decreasing NH4, SOC and pH. In the area with pigs the spatial variability of N, P and CE was influenced by the distance to the service, with no significant influence of distance on the SOC and pH. The system generated spatial heterogeneity, increasing ecological risks associated with loss of N, P and decreased SOC, which suggests that the management should be modified in order to improve the potential biophysical sustainability.