Özet:
Mine soils in southeast Spain have scarce vegetation due to very poor properties such as extremely low soil
organic matter (SOM) (< 0.6 g carbon kg-1 soil), low pH, high salinity and metal contents. Also in southeast
Spain, there is an economically-important pig husbandry faced with challenges to manage the large volumes of
industry-generated animal wastes. This study will present the results of a leaching experiment to assess the
retention and release of nitrogen and carbon from pig manure added to undisturbed column of mine soil. We
excavated three columns (15-cm diameter and 30-cm length) from a representative mined site. The columns
were amended with single (7 % by mass) and double doses of pig manure, and leached weekly with distilled
water for 10 weeks to simulate annual rainfall events in the study area. Leachates were collected and analyzed
for pH, electrical conductivity, redox potential, and contents of selected anions and metals. However, we will
limit this presentation to carbon and nitrogen to quantify the potential contribution of pig manure addition to the
build up soil organic matter in mine soils. Results showed that after addition of pig manure in the soil surface,
soil pH increased from 2.2 to 4.0 after 11 weeks (single dose) and to 5.2 at week 21 (double doses). Significant
increased were observed in total nitrogen contents in both single and double doses, 1.14 g kg-1 (900 %) and 1.40
g kg-1 (1100 %), respectively. Total carbon contents increased to 18.6 g kg-1 (3200%) in single dose and to 16.4
g kg-1 (2800%) in double doses. Nitrogen and carbon in soils had weekly rate of increases of 0.1 and 2.0 g kg-1,
respectively. Moreover, C/N ratio increased from 5 to 12 at the end of the experiment. Leachates had
significantly higher weekly release of NO3- than total dissolved organic carbon (DOC) during the first 6 weeks
of leaching. Weekly rate of releases (mg L-1) were 127 (NO3-) and 5.2 (DOC) in single dose, and 35 (NO3-)
and 2.8 (DOC) for double doses. Leachates contained NO3- less than the 50 mg L-1 threshold established by
FAO. These results suggest that addition of pig manure may significantly accelerate the build up of SOM in
mine soils without endangering the release of NO3- into sub-soil or groundwater in semiarid regions. Once there
is sufficient SOM, mine soils will have an environment hospitable to various ecosystems including plant
colonization and microbial community needed for its physical stability. Pig manure amendment of mine soils
can be an ecologically-sound means of managing the large volume of wastes generated by the pig industry in
southeast Spain.
