成垄压实施肥对氮素运移及氮肥利用率的影响

黄土高原地区夏玉米生长正逢雨季，是N素淋溶的主要时期，为此提出氮肥施用的成垄压实法，通过连续两年的田间小区试验，研究了夏玉米生长期成垄压实施肥方式下夏玉米产量和氮肥利用率，以及土壤NO3^--N迁移规律，并结合室内模拟实验探讨了该施肥法的影响因素。结果表明，在供水量接近研究区同期多年平均降雨量(370mm)的年份，平地施肥条件下，NO3^--N可被淋溶至90cm以下的土层；而成垄压实施肥可明显减少施肥区NO3^--N随入渗水分向土壤深层迁移，至60cm以下土层，土壤NO3^--N含量小于10mg·kg^-1，NO3^--N主要累积于近地表20～40cm土层，该土层土壤NO3^--N含量约为80～90mg·kg^-1。成垄压实施肥法局部存在的大容重障碍层对作物生长发育无影响在240.0kgN·hm^-2施氮量条件下，成垄压实较平地施肥没有显著提高玉米生物产量和经济产量，但却能极显著地增加作物吸氮量，使氮肥利用率提高9％左右。成垄压实施肥条件下，障碍层容重对NO3^--N迁移影响明显，随障碍层容重的增加，NO3^--N迁移深度减小，大田条件下，垄坡度对NO3^--N迁移影响不明显。

Impact of localized compaction and ridge fertilization on field nitrate transport and nitrate use efficiency

The primary season of nitrate leaching in the Loess Plateau region is the monsoon, which is caused by heavy rainfall during the growth season of corn (Zea mays L.). Nitrate leaching to groundwater is an increasing concern in agriculture, and is one of the major nitrogen losing ways in dryland farming system. Localized compaction and ridge fertilization is a method for nitrogen fertilizer application, by which, less fertilizer leaching would occur. The NO3(-)-N transport in soil profile, corn yields and nitrogen use efficiency under localized compaction and ridge fertilization were investigated through two years field study. The factors that affect NO3(-)-N transport under localized compaction and ridge fertilization were studied, combined with simulated experiment. The results showed that NO3(-)-N was leached to below 90 cm in plat fertilization in the year of about 370 mm rainfall, a mean precipitation during the season, while the NO3(-)-N leakage of the fertilizer zone was reduced by localized compaction and ridge fertilization, as a result that the NO3(-)-N concentration below 60 cm was less than 10 mg.kg-1, and NO3(-)-N accumulated in 20-40 cm with a concentration 80-90 mg.kg-1. There was no significant difference in yield between application methods with 240.0 kg N.hm-2. However, the absorbed amount of nitrogen was improved significantly by localized compaction and ridge fertilization, and the nitrogen use efficiency was increased by 9%. The bulk density of the barriers had an evident effect on NO3(-)-N transport under localized compaction and ridge fertilization, but the effect of ridge slope was insignificant.