Fate Of Fertilizer Nitrogen And Gaseous N Loss In Winter Wheat-Summer Maize Rotation System In North China Plain

Along with the fast development of intensive agriculture, the chemical fertilizer'sinput is continually increasing and also obviously is higher than the national average levelin the North China plain. The rate of nitrogen fertilizer application was far higher than theCrops demand level in the majority areas. It caused the low efficiency of nitrogen fertilizer,the largely nitrate nitrogen residue in soil, nitrogen loss increase and so on. Moreover, itbrought the enormous pressure to the environment. Currently, the fate of nitrogen and thepathways of nitrogen loss still lacked the systematic quantitative field research in situexamination on dry farming system of the north. This research established the field¹⁵N-micropolt experiments, used continuous air flow enclosure method, the closed staticchamber measurement and the soil profile sampling technology, quantitative studied on thefate of nitrogen and the pathways of nitrogen loss after application in winterwheat-summer maize rotation system in situ examination. It provided the theory basis forrational application of nitrogen fertilizer, reducing the gaseous loss and raising theefficiency of nitrogen fertilizer. The main results were as follows:(1) Following nitrogen application rates increasing, the crops yield increasedunceasingly, when it achieved certain quantity, increasing rate of nitrogen fertilizerapplication can not promote the yield growth. The relationship between grain yield andnitrogen application rates could be simulated by using linear-platform model. In the winterwheat season, the fate of nitrogen displayed crops uptake＞soil residue＞fertilizer loss underthe low nitrogen application rate, under the high nitrogen application rate, soilresidue＞crops uptake＞fertilizer loss. Namely along with the nitrogen application rateincrease, the crops uptake from nitrogen fertilizer increases, the uptake form soil reducedgradually, the residual fertilizer nitrogen remarkable increase, the soil nitrogen totalbalance from wane to surplus. NO₃^--N in root zone soil also transformed cumulate fromconsuming nitrogen before seeding. The nitrogen recovery rate decreased. Between thenitrogen application rates and the nitrogen fertilizer loss presented the linear relation.Moreover, the nitrogen application rates and the residual NO₃^--N in rhizosphere soildisplayed the platform -linear relation, had Nmin cumulate cushion region. (2) In the winter wheat-summer maize rotation system, the ammonia volatilizationmainly occurred in application or irrigation after in one to two weeks. The peak ofammonia volatilization occurred within 1～4 days. Ammonia loss increased with nitrogenapplication rates. The fertilizer nitrogen loss due to the ammonia volatilization was alsogradually increasing. Ammonia volatilization loss was mainly in the summer maize season.The ratio was 53.5%～62.7% in the whole rotation system. The temperature and the soilmoisture content were the important factors with the ammonia volatilization.(3) The N₂O emission showed significant seasonal variation in winter wheat-summermaize rotation system in field. The peak of N₂O emission appeared in a week after basalfertilizer or top-dressing. The seedling stage was the main N₂O emission time of winterwheat, next was the elongating stage. The least was between over-winter stage andelongating stage. In the summer maize, it had two peak N₂O emissions to appear afterapplication in three leaf stage and ten leaf stage. The three leaf topdressing was higher thanthe ten leaf topdressing Of N₂O emission. The total quantity separately to occupy the entiregrowth season was 55.1% and 19.4% in two weeks after topdressing. The peak of N₂Oemission was summer maize obviously to be higher than the winter wheat season, thesummer maize was the main season of N₂O emission, the nitrogen loss proportion was thehighest in three leaf stage topdressing.(4) The KN9204 (high-N efficiency variety) was higher than the HN822 (Hebeimainly to plant variety) in grain yield, biomass, nitrogen recovery rate and so on. Innitrogen accumulation and nitrogen use efficiency (NUE), under the low nitrogenapplication rate (75 kg N/hm²) displayed higher than the HN822. It indicated the highlyefficiency of KN9204 variety in the low nitrogen rate. KN9204 improved the nitrogen useefficiency from the agronomy angle.