华北二月兰-春玉米轮作体系中土壤硝态氮的时空变化特征

Temporal and spatial variations of soil NO^-_3-N in Orychophragmus violaceus /spring maize rotation system in North China

二月兰-春玉米轮作生产体系是近年来为解决华北地区出现的大面积冬闲田而提出的冬绿肥-春玉米生产新模式.本文依托定位试验,研究了该体系从二月兰翻压到玉米收获期间的土壤硝态氮时空变化特征.结果表明:土壤硝态氮含量呈玉米生育前期高后期低的时间变化特征和硝态氮含量峰值随着生育期的推移逐渐下移的空间变化特征,且土壤硝态氮含量随施肥量的增加而显著增加.翻压二月兰对土壤硝态氮含量的时空变化有一定影响,冬春季种植二月兰可降低0~180 cm土壤硝态氮累积量;二月兰翻压后,春玉米苗期与喇叭口期土壤硝态氮规律基本一致,主要集中在0~20 cm土层,0~100 cm土壤剖面为有二月兰处理高于无二月兰处理,100~180 cm土壤剖面则为有二月兰处理低于无二月兰处理;抽雄期以后,土壤硝态氮含量普遍较低,100~180 cm土层土壤硝态氮含量为有二月兰处理略高于无二月兰处理.总体上,翻压二月兰可以增加0~180 cm土层土壤硝态氮保蓄量.

The February orchid （Orychophragmus violaceus）spring maize rotation system is established to resolve the problems caused by the expansion of fallow fields in North China. Based on a sitespecific experiment, temporal and spatial variations of soil NO3--N were investigated during the period from February orchid incorporation to maize harvest. The results showed that the nitrate content in soil profiles not only showed a temporal characteristic, i.e., increasing at the beginning of the maize season and decreasing then after, but also showed a spatial characteristic, i.e., the gradual occurrence of the peak of nitrate content from shallower to deeper layer with the growth season of maize. Meanwhile, incorporation of February orchid could affect temporal and spatial variations of soil NO3--N. February orchid planting reduced the soil NO3--N accumulation in the profile of 0-180 cm. After incorporation of February orchid, similar characteristics were observed at the seedling and bell stages of maize, i.e., the soil NO3--N mainly stayed in the profile of 0-20 cm, and NO3--N concentrations in the treatments with February orchid were higher in 0-100 cm layer and lower in 100-180 cm layer than those of the treatments without February orchid. After tasseling stage, opposite phenomena were found, and the soil NO3--N content was all relative low. Overall, incorporation of February orchid could increase the storage capacity of soil NO3--N in the profile of 0-180 cm.