Nitrification regulation by a new organic compost in ultisols of a flue-cured tobacco plantation

Abstract

Nitrate nitrogen (nitrate-N) is crucial for the development of tobacco quality. However, how to enhancing soil nitrification in tobacco plantation is still an immediate concern that requires attention. This study aimed to examine the impact of mixed organic manure on soil nitrification in tobacco cultivation regions. We selected an Ultisols field, which was planted with tobacco from Yunnan province, to explore the impact of adding various organic manures (F1-F6: regular organic manures, F7: mixed organic compost which was derived from crop residues), on soil gross N mineralization and nitrification. This study was conducted through a 75-day indoor leaching experiment, with constant temperature (25°C) and humidity (65% of field water capacity). The results showed that F4 significantly (p < .05) enhanced soil N mineralization, and had the highest mineralized-N and potentially releasable mineralized-N (N₀) due to its highest organic carbon (OC) and total-N, which amounted to 422 mg kg¯¹ and 705.7 mg kg¯¹ , respectively. F7 exhibited a significant increase (p < .05) in the rate of soil N mineralization, with the highest first-order mineralization rate constant (k1) of 0.090 d¯¹. Moreover, it displayed a substantial increase (p < .05) in nitrate-N content and potentially releasable nitrate-N (Np), measuring 41.5 mg kg¯¹ and 41.3 mg kg¯¹, respectively. Furthermore, F7 exhibited the highest first-order nitrification rate constant (k2) of 0.076 d¯¹ . It also demonstrated a considerably higher net nitrate-N/mineralized-N ratio of 33.5%, which was significantly (p < .05) greater than that of F1-F6 (nitrate-N/mineralized-N ratio: −7.06 to 1.86%). At day 15 and day 45, F7 exhibited the highest nitrate-N concentration and nitrate-N/mineralized-N ratio (28.1 mg kg¯¹ and 49.7%) in comparison to F1-F6, which had lower nitrate-N concentrations (ranging from 0.4 to 6.9 mg kg¯¹ ) and nitrate-N/mineralized-N ratios (ranging from 0.4 to 11.9%). These results indicate that the addition of mixed organic compost significantly enhances soil nitrification compared to regular organic manures. Therefore, it suggests that incorporating mixed organic compost improves soil nitrification in Ultisols.