Nitrogen dynamics as a function of soil types, compaction, and moisture

by Saurav Das, Ankita Mohapatra, Karubakee Sahu, Dinesh Panday, Deepak Ghimire, Bijesh Maharjan

In this study, the complex interactions between soil types, compaction, and moisture on nitrogen (N) transformation processes such as ammonia (NH₃) volatilization, ammonification, nitrification, and denitrification were examined over a 30-day period using a simulated column approach. Two soil types: loam, and sandy loam, were subjected to three compaction treatments—control, surface, and sub-surface compaction—and two moisture regimes, dry and wet. Liquid urea ammonium nitrate (32-0-0) was used as the N fertilizer source at a rate of 200 kg N ha^-1. Key indicators of N transformations were measured, including residual concentrations of ammonium (NH₄-N) and nitrate (NO₃-N), NO₃-N leaching, NH₃ volatilization, and nitrous oxide (N₂O) emissions. Findings revealed that compaction significantly increased residual NH₄-N concentrations in deeper soil profiles, with the highest 190.80 mg kg^-1 recorded in loam soil under sub-surface compaction and dry conditions. Nitrification rates decreased across both soil types due to compaction, evidenced by elevated residual NH₄-N levels. Increased NO₃-N leaching was observed in loam soil (178.06 mg L^-1), greater than sandy loam (81.11 mg L^-1), due to initial higher residual NO₃^- in loam soil. The interaction of compaction and moisture most affected N₂O emissions, with the highest emissions in control treatments during dry weather at 2.88 kg ha ^-1. Additionally, higher NH₃ volatilization was noted in moist sandy loam soil under control conditions at 19.64 kg ha ^-1. These results highlight the necessity of considering soil texture, moisture, and compaction in implementing sustainable N management strategies in agriculture and suggest recommendations such as avoiding broadcast application in moist sandy loam and loam soil to mitigate NH₃ volatilization and enhance N use efficiency, as well as advocating for readjustment of fertilizer rate based on organic matter content to reduce potential NO₃-N leaching and N₂O emissions, particularly in loam soil.