| China is the world’s largest production and consumption of nitrogen fertilizer, accounting for one-third of global nitrogen fertilizer amount. Seven percent of the amount is used in Chinese rice production, but nitrogen utilization rate of rice in China is only about30%. Nitrogen fertilizer cannot be completely absorbed by crops. Ammonia volatilization is one of the main reasons of nitrogen fertilizer loss; greenhouse gases releasing in paddy fields contributes to global warming. How to increase rice production, while reducing fertilizer losses and greenhouse gases releasing to maintain ecological balance is a current crop research hotspot and difficulty.Two season field experiments were conducted under high and super-high yield conditions in Yong’an Town, Liuyang city of Hunan province in2010. Treatments included four cultivation models and one control plot T1.Four cultivation models which were expected to establish different yields were Local traditional cultivation T2, high-yield-and-efficiency cultivation T3,super-yield cultivation T4and high-efficiency-and-super-yield cultivation T5. The rice characteristics of different treatments in terms of yield, nitrogen use efficiency, ammonia volatilization, and greenhouse gas emission were analyzed in order to provide the theoretical and practical basis of the optimal rice cultivation technique. Results are as follows:(1) The grain yield was T4> T5> T3> T2among different cultivation models in two seasons. Nitrogen fertilizer agronomy efficiency of T2, T3, T4, T5were respectively17.19kg/kg,31.64kg/kg,22.95kg/kg,22.64kg/kg in early season, and6.09kg/kg,15.77kg/kg,20.63kg/kg,18.89kg/kg in late season. Nitrogen recovery efficiency of T2, T3, T4, T5were respectively34.1%,56.5%,46.4%,46.4%in early season, and13.5%,39.1%,55.4%,51.8%in late season. The grain yield, nitrogen agronomy efficiency and nitrogen recovery efficiency of T3, T4, and T5were significantly higher than those of T2.(2) Amount of volatilized ammonia in T2, T3, T4, and T5were respectively58.80kg/ha,38.15kg/ha,53.45kg/ha,43.34kg/ha in early season, and97.29kg/ha,56.05kg/ha,74.23kg/ha,61.70kg/ha in late season. The ratio of ammonia volatilization to total nitrogen in T2, T3, T4, T5were respectively39.20%,31.79%,29.70%,28.90%in early season, and respectively58.97%,41.52%,38.07%,37.79%in late season. Correlation coefficients between ammonia volatilization and nitrogen supplied amount were highly significant and0.930and0.910for early and late seasons, respectively. (3) The ratio of ammonia volatilization after early stage of fertilization (basal and topdressing at tillering stage) in T2, T3, T4, and T5respectively accounted for99.60%,86.94%,87.54%,92.23%in early season; and99.99%,93.55%,92.61%,94.74%in late season. Most of ammonia volatilization was from basal fertilizer application and at tillering stage. Postponing the application significantly reduced the loss of nitrogen due to volatilization..(4) Monitoring ammonia nitrogen and nitrate nitrogen concentration in the field water revealed that ammonia nitrogen and nitrate nitrogen concentration increased after fertilizer application. Although nitrogen fertilizer is essential in rice production, the high concentration ammonia nitrogen are not fully utilized by the crop and are lost via volatilization and nitrification.(5) Monitoring of greenhouse gas showed that, compared with T2, T3and T4had no significant difference in CH4emissions in the two seasons and in N2O emissions in early season, but T4, T5were significantly higher in N2O emissions than T2in late season. CH4and N2O emissions of T5in two seasons were higher than other models, which may be related with the incorporation of rice straw in the plot.In this study, through optimizing cultivation patterns, the yield and nitrogen use efficiency of T3were significantly higher than that of T2, and ammonia volatilization was minimum in all models, greenhouse gas emissions had no significant difference with T2.So T3is suitable for demonstration and application in large area. |
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