Chapter 14 - Impacts of Raw and Purified Pig Slurry on Carbon and Nitrogen Contents in Mediterranean Agricultural Soil

Abstract

The agricultural valorization for pig slurry (PS) used in soils as an amendment and nutrient source contributes to management this residue. As a nutrient source, PS is considered potentially valuable. Conversely, the overapplication of PS in soils could lead to environmental problems such as water and soil pollution by nitrates leaching, especially in vulnerable zones. However, if PS has a sustainable use and rational application on the land, it can trigger many benefits related to soil quality improvement in dryland areas such as Mediterranean soils. Particularly, it can increase the total amount of soil organic matter, microbial biomass, and macro and micronutrients. A low-cost system as horizontal subsurface flow constructed wetlands (HSFCW) used to purify PS minimize potential pollutants, and aid to restoring soil properties. It is a sustainable environmental practice. The objectives were to study the application of raw PS and different treated PS in agricultural soil focusing on the impact of nutrients to soil, especially nitrogen, carbon, and available Zn, Cu, and P. The NO3− and NH4+ contents showed a similar pattern when different treated pig slurries were applied to soils. The ratio C/N experienced any significant variation after PS application and the basal respiration of soil was reduced. The addition of PS from a hydraulic retention time of three and 7 days entailed greater Cu bioavailability in soil. As a conclusion, the addition of different stages of PS to the soil did not eject a negative effect in soil macro and micronutrient contents, especially on C and N dynamics.