不同耕作施氮处理对稻田N_(2)O通量和田面水中无机氮的影响

Effects of Different Tillage and Nitrogen Applications on N_(2)O Emission and Mineral Nitrogen in Surface Water of Paddy Field

【目的】探索不同耕作施氮处理对稻田氧化亚氮(N_(2)O)通量和田面水中无机氮质量浓度的影响。【方法】设置4种耕作方式(免耕T、微耕C、旋耕R和粉垄S)以及2个施氮量(常规施氮225 kg/hm^(2)(N1)和减量施氮150 kg/hm^(2)(N2)的双季水稻田间试验,测定不同时期施用氮肥后稻田N_(2)O通量以及田面水中无机氮质量浓度,分析不同时期施用氮肥后1、3、5 d稻田N_(2)O通量与田面水中无机氮质量浓度之间的关系。【结果】①不同时期施用氮肥后田面水中的铵态氮(NH_(4)^(+)-N)质量浓度较高,施用氮肥后1 d田面水中的NH_(4)^(+)-N快速上升到峰值后迅速下降。分蘖期和孕穗期施用氮肥后,TN1(免耕常规施氮)处理田面水中的NH_(4)^(+)-N较其他处理提高4.7%~532.6%。氮肥作基肥以及在分蘖期和孕穗期施用后,所有处理田面水中的硝态氮(NO_(3)^(-)-N)和亚硝态氮(NO_(2)^(-)-N)质量浓度较低,NO_(3)^(-)-N质量浓度在0.08~0.20μg/mL之间,NO_(2)^(-)-N质量浓度低于0.12μg/mL。②氮肥作基肥以及在分蘖期和孕穗期施用后,TN_(2)处理稻田N_(2)O通量较其他处理低。③稻田N_(2)O通量与不同时期施用氮肥后1~5 d田面水中NH_(4)^(+)-N质量浓度显著负相关,相关系数为-0.509~-0.300。【结论】施用氮肥后NH_(4)^(+)-N是田面水中无机氮的主要形态,施用氮肥后1~5 d田面水中的NH_(4)^(+)-N质量浓度显著影响稻田N_(2)O通量。

【Objective】Rice in southern China is traditionally grown in paddy fields and improving its fertilizer use efficiency and reducing greenhouse emissions is critical to helping achieve the mandatory goal of zero-increase in agrochemical application without compromising crop yield.This paper presents the findings of an experimental study on combined effect of tillage and nitrogen application on N_(2)O emission and mineral N concentrations in surface water of the paddy fields.【Method】The experiment was conducted in a double-cropping rice field and involved four tillage treatments:zero tillage(T),micro tillage(C),rotary tillage(R),and smash ridging tillage(S).For each tillage treatment,there were two N fertilizations:conventional N application at 1225 kg/hm^(2)(N1)and reducing N application to 150 kg/hm^(2)(N_(2)).N_(2)O emission and mineral N concentration in the surface water in each treatment were measured 1,3,and 5 days after N fertilization at different growth stages of the rice.【Result】①One day after N fertilization,ammonium concentration in the surface water increased rapidly to a peak one and then declined quickly.In the conventional fertilization(N1)where N was applied at both tillering and booting stage,zero-tillage increased ammonium concentration in the surface water by 4.7%~532.6%,compared to other treatments.Overall,nitrate and nitrite concentrations in the surface water of all treatments were in the range 0.08~0.20μg/mL and less than 0.12μg/mL,respectively.②Reducing N application and applying it as basal fertilization and topdressing at tillering and booting stages,TN2 reduced N_(2)O emission more than other tillage treatments.③N_(2)O emission was negatively correlated to ammonium concentration in the surface water 1~5 days after N fertilization,with the correlation coefficient varying from-0.509~-0.300,depending on the timing of the fertilization.【Conclusion】After N fertilization,ammonium became the primary inorganic nitrogen in the surface water.Ammonium concentration of the surface water 1~5 days after the fertilization impacted N_(2)O emissions,irrespective of the timing of the fertilization.