Nitrogen Dynamic and Leaching in Calcareous Soils Amended With Pig Slurry

This chapter evaluates the N transformations in calcareous soil after a pig slurry application in order to propose measures to reduce the leaching of certain nitrogen compounds. For this purpose, nine undisturbed soil columns were amended with unprocessed pig slurry using three doses (i.e., 0, 170 (LD) and 510 (HD)kg Nha¹). Electrical conductivity of leachates ranged from 0.23 to 1.51dSm^?1; pH showed values of 7.00-8.30, and NH₄⁺-N content was always 1mgL¹. In the amended soils, there were N volatilization losses >l1gm² and nitrification profits >5000mgm² due to the mineralization of organic nitrogen and the oxidation of NH₄⁺ as a consequence of biological activity. The net balance in the columns showed N losses (volatilization and denitrification) from soil, being favored by high soil pH, CaCO₃ content, high concentrations of NH₄⁺ and organic compounds in the pig slurry, high temperatures, and leaching events by rainfall simulation. In the end, 85% of the initial total N provided by PS was lost from soil for LD and HD, mainly by volatilization or denitrification. Similarly for both doses, the percentage of the initial total N lost by leaching was very low (~4%). The high dose showed gains of NO₃¹-N and losses of NH₄⁺-N and organic N, only slightly higher than the low dose. The highest N losses in the amended soil occured in weeks 3-11 after the pig slurry application; during this period a conscious environmental management of the soil-water-plant system is essential to avoid N losses by adding nitrification inhibitors and scheduling nutrient uptake and fertirrigation.