Nitrogen Dynamic and Leaching in Calcareous Soils Amended With Pig Slurry

Abstract 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 N ha − 1 ). Electrical conductivity of leachates ranged from 0.23 to 1.51 dS m − 1 ; pH showed values of 7.00–8.30, and NH 4 + -N content was always ≤ 1 mg L − 1 . In the amended soils, there were N volatilization losses > 1 g m − 2 and nitrification profits > 5000 mg m − 2 due to the mineralization of organic nitrogen and the oxidation of NH 4 + 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, CaCO 3 content, high concentrations of NH 4 + 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 NO 3 − -N and losses of NH 4 + -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.