Study On The Fate Of Nitrogen In February Orchid/Spring Maize Rotation System In North China

With the decreasing of winter wheat cultivated area and the increasing plant area of one spring maize a year mode in Beijing-Tianjin-Hebei area of North China, numbers of environmental problems such as incomplete utilization of light and heat resources in winter and spring, land vacancy, soil drought and wind erosion are emerging. A new plant system named February Orchid-spring maize rotation system in which February Orchid is used as green manure for spring maize was proposed in order to alleviate these problems.Based on this pattern, a field experiment was conducted to study the effects of plantation and incorporation of February Orchid on ammonia volatilization and spatial variation of soil nitrate at different growth stages of maize. Nitrogen uptake and balance were also investigated in the experiment. Eight treatments were included in the experiment, with4levels of fertilization combined with and without green manure. The4levels of fertilization were0%,70%,85%,100%of local conventional amount, respectively. The key conclusions are as follows:1. Ammonia volatilization was one of the most important ways for nitrogen loss, and was mainly affected by fertilization. Incorporation of February Orchid did not change the total ammonia volatilization obviously. Ammonia volatilization amounts at the basal and the top dressing fertilization stages were3.12%～6.80%and93.20%-96.88%of the total ammonia volatilization amounts, respectively. At the basal fertilization stage, ammonia volatilization amounts were0.94～3.27kg/hm2, accounting for1.34%～2.91%of the applied N. Ammonia volatilization amounts of treatments with February Orchid were averagely1.04kg/hm2higher than those of treatments without February Orchid at this stage. At the top dressing fertilization stage, ammonia volatilization amounts were27.17～46.81kg/hm2, accounting for34.50%～41.61%of total N application, while no remarkable differences were detected between the treatments with or without February Orchid.2. Soil nitrate contents increased significantly with the increase of fertilization amounts. Nitrate retaining in soil occupied an important position in the fate of nitrogen within the system. Incorporation of February Orchid could effectively improve the nitrate content in0～180cm soil. The nitrate content in soil profiles not only showed a temporal characteristic, increased at the beginning of the maize season and decreased then after, but also showed a spatial characteristic as well, the peak of nitrate content appeared gradually from shallower layer to deeper layer with the growth season of maize. During the earlier growth stages, nitrate accumulations of February Orchid treatments were higher in0～100cm layers and lower in100-180cm layers than those of no February Orchid treatments. After tasseling stage, opposite phenomena were found.3. Incorporation of February Orchid could improve spring maize yields, N accumulation in maize, and nitrogen use efficiency. Under the same nitrogen application levels, compared with those in the treatments without February Orchid, yields of spring maize in the treatments with February Orchid were increased by12.07%,16.76%and17.07%, nitrogen recovery efficiencies of spring maize were higher by13.78,20.80and17.00percentage points, and nitrogen agronomic efficiency of spring maize were increased by6.85,7.60,6.75kg/kg, respectively.4. Under the same fertilization level compared with those treatments without February Orchid, the amounts of fate unknown nitrogen in0～100cm soil profile were higher, and the amounts of fate unknown nitrogen in0～100cm soil profile retained much more than in100～180cm profile in the February Orchid treatments.