【摘要】 为研究河套灌区盐碱农田不同施氮量在冻融作用后对翌年春播前土壤肥力的影响效应,结合翌年土壤肥力状况确定当地适宜的施氮量。采用田间试验的方法,共设置4个施氮水平（高氮N₃:325 kg/hm²;中氮N₂:225 kg/hm²;低氮N₁:125 kg/hm²;不施氮N₀）研究冻融期内水盐时空分布、全氮、碱解氮以及有机质含量的变化规律,并采用主成分分析法对翌年春播前土壤肥力进行综合评价。结果表明:（1）秋浇后,土壤含水率显著高于秋浇前,表层土壤含水率增加,开始冻结时,水分向表层积聚,随着温度降低水分自表层向深层冻结,各处理灌溉水平相同,不同施氮处理之间对土壤含水率的影响不显著,土壤墒情满足作物对水分的需求;秋收后耕层土壤含盐率随生育期内施氮量的增加而增加,施氮量越大土壤含盐率递增。秋浇后大量盐分被淋洗,融化后盐分受到融冻水的下渗和蒸发的共同作用,使得各处理表层含盐率为N₀（0.14%）<N₁（0.17%）<N₂（0.19%）<N₃（0.45%）,高氮处理发生土壤次生盐碱化;（2）冻融期内土壤养分主要集中在土壤表层（0—20 cm）,土壤中的全氮、碱解氮和有机质含量在冻融期内呈现先增大后减小的变化规律,最大值出现在最大冻深期,说明冻结作用有助于全氮、碱解氮以及有机质的累积;（3）运用主成分分析法对翌年春播前土壤肥力进行综合评价,在PC1和PC2上有机质、有机碳以及全磷有较高的因子负荷,对土壤肥力的贡献率较高。从综合得分情况来看（N₃<N₀<N₁<N₂）,高氮处理的土壤肥力低下,中氮处理综合得分最高,土壤肥力情况最佳,根据综合分析推荐该地区玉米生育期内施氮肥量为225 kg/hm²（基肥20%、拔节期40%和抽雄期40%）左右,有利于翌年春播前土壤培肥,使农业得以持续的发展。更多还原

【Abstract】 Studying the effects of different nitrogen application amount on soil fertility before spring sowing could help determine the suitable nitrogen application amount in Hetao Irrigation Area. In this study, four nitrogen application levels（high-nitrogen N₃: 325 kg/hm², medium-nitrogen N₂: 225 kg/hm², low-nitrogen N₁: 125 kg/hm², and no nitrogen application N₀） were set up in the field experiment. The spatial and temporal distribution of water and salt and the changes of total nitrogen, alkali-hydrolysis nitrogen and organic matter contents were studied during freezing-thawing period. Then the soil fertility was evaluated by principal component analysis. The results showed: Firstly, after autumn water application, soil moisture content was significantly higher than before. The surface soil moisture content increased. When it just began to freeze, soil water accumulated to surface layer, and then froze to the deeper layer as the temperature reduced. The irrigation rates were the same in different treatments. The impacts of different nitrogen treatments on the soil moisture content was not significant. The soil moisture could meet the crop water demand. The soil salinities increased with the increasing nitrogen application rates during the growth period. A large amount of salt was leaching when water was applied in autumn. Soil salt was subjected to the combined effects of infiltration and evaporation during the water thawing, resulting in that the surface soil salinities were N₀（0.14%）<N₁（0.17%）<N₂ （0.19%）<N₃（0.45%）. Secondly, during freeze-thaw period, soil nutrients were mainly concentrated in the surface soil layer of 0—20 cm. During the freeze-thaw period, the contents of total nitrogen, alkali-hydrolysis and organic matter in the soil showed a change pattern of first increasing and then decreasing. The maximum value occurred in the maximum freeze-thaw period, indicating that freezing helped the accumulation of total nitrogen, alkali-hydrolysis and organic matter. The last, soil fertility was comprehensively evaluated before the next spring sowing. Organic matter, organic carbon and total phosphorus on PC1 and PC2 had higher factor loads, contributing to soil fertility. Considering from the composite scores（N₃<N₀<N₁<N₂）, high nitrogen treatment led to the low soil fertility, and the highest scores were given in the medium nitrogen treatment, resulting in the highest soil fertility. Therefore, it is, recommended that the nitrogen application rate should be around 225 kg/hm² for the maize growth, and 20% for the basal, 40% for the jointing stage and 40% for the tasseling stage respectively. This fertilization will be beneficial for the improvement of the soil fertility in the following spring sowing and also for the agricultural sustainable development.更多还原