Environmental effects of agronomic recycling of pig manure: Nitrogen dynamic in the soil-water-plant system.

摘要

The consequences of N are spreading and affecting regional and globally to the health of agroecosystems and biogeochemical cycles. The agronomic recycling of pig slurry is a traditional practice whose study is crucial both technically and environmentally in semiarid climate conditions and from the point of view of the applicable law. For that reason it was interesting in this thesis to apply different doses of manure in soils: 170 (Directive 91/676/EEC and RD 261/1996), 340, 510 and 1700 kg N per ha per year and to study the properties of the soil-water-plant system, especially those properties related to the N cycle. The results highlighted an increase in the biomass yield of barley in the study area of Dona Ines for the application rates of 170 kg N (9543 kg ha-1) and 340 kg N (13 420 kg ha -1) compared to the control treatment (7990 kg ha-1) at the 2010 harvest. The nitrification of soil incubated with manure built up throughout the study period up to 39-45 mg kg-1 for the control and treatment dose of 170 kg N ha-1 and up to 54-285 mg kg-1 for the dose of 1700 kg N ha-1. The leachates results varied during the 12 weeks of experimentation, EC from 0.23 to 1.51 dS m-1, pH from 7.0 to 8.3 and the NH4 +-N values were equal or less than 1 mg L-1. In conclusion the long-term use of recommended doses is very useful to reduce costs in chemical fertilizers and to maintain the soil nutrient levels, with nitrification and mineralization rates consistent with the temporality of the crops. The use of non-recommended doses or overdoses of manure up to 10 times the recommended dose involves powerful environmental consequences such as N gas emissions and N leaching of NO3--N and organic N up to 100 days after application. Under these conditions the N dynamic is strongly influenced by the soil properties such as the salt and carbonates contents.