Volatilized N-NH3, N, and C stocks in soil after green manuring of coffee crops

Abstract

Volatilization of nitrogen ammonia (N-NH3) and rapid incorporation of mineralized nitrogen (N) into soil organic matter fractions can reduce the efficiency of green manuring. The objective of this study was to characterize N-NH3 loss through volatilization and the changes in carbon (C) and N stocks in soil fertilized with Crotalaria juncea and ammonium sulfate during coffee plant cultivation. The N-NH3 collectors were installed and evaluated at 1, 2, 3, 4, 5, 6, 9, 12, 15, 18, 25, 32, 67 and 123 days after their installation. Total organic carbon (TOC) and total nitrogen (TN) in the 0–5- and 5–10-cm soil layers were evaluated at 0, 60, 120, 180, 240, and 300 days after fertilization. After 9 days, 20.83 kg ha-1 (N-NH3) had volatilized from the 41.88 kg ha-1 observed at the end of the evaluation period. The TOC stock in both soil layers was 5.81 Mg ha-1, and after 300 days, the stocks were 8.84 and 8.36 Mg ha-1 for the 0–5 and 5–10 cm layers, respectively. The TN stock in the 0–5 cm layer increased from 1.74 to 1.98 Mg ha-1 over 60 days, and then decreased. There was no time dependency in the TN stock in the 5–10 cm layer. Volatilization of N-NH3 was rapid but low. The increase in TOC stocks was not followed by an increase in TN stocks.