[Effects of organic material amendment on vegetable soil nitrate content and nitrogenous gases emission under flooding condition].

Applying large amount of nitrogen fertilizer into vegetable field can induce soil NO(3-)-N accumulation, while rapidly removing the accumulated NO(3-)-N can improve vegetable soil quality and extend its service duration. In this study, a vegetable soil containing 360 mg N x kg(-1) was amended with 0, 2500, 5000, and 7500 kg C x hm(-2) of ryegrass (noted as CK, C2500, C5000, and C7500), respectively, and incubated in a thermostat at 30 degrees C for 240 h under flooding condition, aimed to investigate the effects of organic material amendment on vegetable soil nitrate concentration and nitrogenous gases emission. By the end of the incubation, the soil NO(3-)-N concentration in CK was still up to 310 mg N x kg(-1). Ryegrass amendment could remove the accumulated NO(3-)-N effectively. In treatments C2500, C5000, and C7500, the duration for the soil NO(3-)-N concentration dropped below 10 mg N x kg(-1) was 240 h, 48 h, and 24 h, respectively. After the amendment of ryegrass, soil pH increased significantly, and soil EC decreased, with the increment and decrement increased with increasing amendment amount of ryegrass. The cumulative emissions of soil N2O and N2 in ryegrass amendment treatments amounted to 270-378 mg N x kg(-1), and the N2O/N2 ratio ranged from 0.6 to 1.5. Incorporating with ryegrass under flooding condition could rapidly remove the accumulated NO(3-)-N in vegetable soil, but the high N2O emission during this process should be attached importance to.