淹水条件下添加有机物料对蔬菜地土壤硝态氮及氮素气体排放的影响

蔬菜地大量施用氮肥可以引起土壤硝态氮积累,导致土壤退化,快速消除土壤积累的硝态氮,可以提高蔬菜地土壤质量,延长其使用时间.在硝态氮(360 mg N·kg-1)积累的蔬菜地土壤中,分别加入0、2500、5000和7500 kg C·hm-2黑麦草(记为CK、C2500、C5000和C7500),淹水条件下,30 ℃恒温室内培养240 h,研究土壤硝态氮含量及氮素气体排放量变化.结果表明:培养结束时,CK处理中土壤硝态氮含量高达310 mg N·kg-1,添加黑麦草能有效地消除土壤中积累的硝态氮,C2500、C5000和C7500处理中土壤硝态氮含量降低至10 mg N·kg-1以下需要的时间分别为240、48和24 h.添加黑麦草显著提高了土壤pH,降低了土壤电导率,其变化幅度随黑麦草添加量的增加而增大.添加黑麦草处理的土壤N2O和N2累积排放量为270 ～378 mg N· kg-1,N2O/N2为0.6 ～1.5.淹水条件下添加黑麦草可快速消除蔬菜地土壤积累的硝态氮,但应充分重视N2O在这一过程中的大量排放.

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.