The Characteristics of Ammonia Volatilization and Crop Yield Under Legume-Wheat Rotation System in Fluvo-Aquic Soil in Northern Henan Province

Based on the long-term rotation experiment, this study explored the characteristics of ammonia volatilization and crop yield change in Fluvo-aquic soil.

The long-term experiment started in 2016, and this study carried out 2023-2024. A randomized block design with five crop rotation treatments were set as: (1) continuous wheat-maize (WMWM); (2) continuous wheat-peanut (WPWP); (3) continuous wheat-soybean (WSWS); (4) 1-year wheat-maize + 1-year wheat-soybean (WMWS); (5) 1-year wheat-maize + 1-year wheat-summer peanut (WMWP). The ammonia volatilization rate (AVR) and cumulative volatilization (ACV), the content of different nitrogen forms in soil, nitrogen content in crop, and crop yield were measured and analyzed.

The ACV in summer-autumn season was higher than that in wheat season, and the AVR in both seasons concentrated in 1st-9th day after fertilization. Under the same fertilization condition, at the summer-autumn season, the AVR peak in WMWM treatment was the highest one with 4.15 kg·hm^-2·d^-1. At the wheat season, the lowest AVR of wheat base fertilizer was observed under WMWS (0.77 kg·hm^-2·d^-1), and the lowest AVR after topdressing fertilizer was under WSWS (0.40 kg·hm^-2·d^-1). The lowest ACV was under WMWP and WMWS during both summer-autumn and wheat seasons, which decreased by 18.7% and 14.8%, 12.5% and 28.6%, respectively, compared with WMWM. In the 0-20 cm soil layer, the content of ammonium, nitrate, and total nitrogen under WPWP and WSWS were significantly higher than those under WMWM during the two seasons. Compared with WMWM, the content of nitrogen in wheat grains under WPWP and WSWS were increased by 12.9% and 17.2%, respectively, and the similar trend was observed in grain nitrogen accumulation, with 135 kg·hm^-2 and 137 kg·hm^-2, respectively. The maize equivalent yield (MEY equal to price yield) under WPWP treatment was significantly higher than other treatments, which was 41.7% higher than that under WMWM treatment. Compare with WMWM, the panicle number (7.0% and 3.5%), kernel number per spike (20.7% and 15.9%), thousand grain weight (5.4% and 4.1%) and yield (10.8% and 10.9%) were enhanced under WPWP and WSWS treatment. During the whole rotation cycle, crops absorbed nitrogen accounted for 43.8%-56.3%, and ammonia volatilization accounted for 1.9%-4.5%. The highest crop absorbed proportion was under WMWP, while the lowest proportion ammonia volatilization was under WSWS.

In the Fluvo-aquic soil area of northern Henan Province, the rotation of wheat and legume crops improved the soil nutrient, reduced the soil ammonia volatilization, increased the nitrogen content and wheat yield, which was recommended as a suitable rotation mode in this area.