Efectos ambientales de la valorización agronómica de purines de ganado porcinodinámica del nitrógeno en el sistema suelo-agua-planta

Abstract

The consequences of N are spreading and affecting the health of agroecosystems and biogeochemical cycles. Future prospects are interesting in both regionally and globally. Whereas N plays a key role in food production, there are few things that can be done to decrease the amount of the anthropogenic N created. From a scientific point of view, efforts should focus on understanding the fate and consequences of the N introduced and increasing the N use efficiency produced where is possible. In countries like Spain and regions such as Murcia which have a high production of livestock waste, fertilizer consumption should be reduced and be exploited as fertilizer and nutrient supply. The agronomic recycling of pig slurry is a traditional practice that is crucial both technically and environmentally study in semiarid climate conditions and applies European and Spanish legislation. For this reason it was interesting in this thesis applied different doses of manure in soils: 170 (legislated by the European Union Directive 91/676/EEC and RD 261/1996), 340, 510 and 1700 kg N per ha and year and study different properties and characteristics of the soil-water-plant system, especially those matters related to N. Other fundamental issues such as the influence of soil fertility , the cereal crop yields, the potential for leaching from N as NO3-, NH4+ and total soluble N and the environmental effects that might arise from the pig slurry application of not recommended doses or discharges of manure in agricultural soils were also evaluated. The results highlight an increase of biomass yield of barley in the study area of Doña Inés for application rates of 170 kg N ha-1 ( 9543 kg ha-1) and 340 kg N ha-1 (13 420 kg ha-1) compared to the control treatment (7990 kg ha-1) in the harvest of 2010. The incubation of amended soils showed that nitrification increased with the incubation time up to 39-45 mg kg-1 for treatments 170 kg N ha-1 and Control and up to 54-285 mg kg-1 for dose 1700 kg N ha-1. Regarding the leachate results, these varied during the 12 weeks of experimentation with values from 0,23 to 1,51 dS m-1 for EC, pH of 7,0 to 8,3 and the NH4+-N values were equal to or less than 1 mg L-1. The study concludes that long term experiments with recommended doses are very useful to reduce costs of chemical fertilizers and to maintain the nutrient levels in soils, with nitrification and mineralization rates consistent with the temporary crops. However, long-term effects of non-recommended doses or overdoses of slurry up to 10 times the recommended dose involve significant environment impacts such as N emissions and N leaching of NO3--N and organic soluble N until 100 days after application. Under these conditions the N dynamic becomes very influenced by soil properties such as the salts content and carbonates.