灌水和施氮对冬小麦根系特征及氮素利用的影响

植株根系的形态和生理特性决定着其获取养分和水分的能力,分析麦田冬小麦根系形态特征、根系活力对水氮的响应及其与地上干物质积累、产量和氮素利用的关系,有利于构建合理的冬小麦根群结构,促进根冠协调生长并提高氮肥利用效率。在麦田定位试验基础上,采用裂区试验设计,设置2个灌溉主处理(W0:全生育期不灌水、W1:拔节期和开花期各灌水1次)以及3个施氮副处理(N0:0 kg hm^(–2)、N180:180 kg hm^(–2)和N300:300 kg hm^(–2))。结果表明:与W0处理相比,W1抑制根长密度的增加,但增加根系平均直径,提高0~20 cm土层根表面积和根干重密度,显著提高根系活力4.98%~22.7%,降低根冠比1.47%~11.25%;2年平均小麦产量、氮素吸收效率和氮肥偏生产力分别提高15.50%、13.40%和14.91%。施氮促进根系生长,与不施氮处理相比,施氮显著提高根系平均直径、根长密度、根表面积、根干重密度和根系活力,降低根冠比。其中N180更有利于根系生长,提高冬小麦根系各形态指标和根系活力,与N300相比,2年平均产量提高2.53%,而氮素吸收效率和氮肥农学效率分别显著提高44.51%和39.37%。相关分析表明,拔节期至开花期根干重密度与产量、氮利用率呈显著正相关关系;根冠比与产量呈显著负相关关系,与氮利用率呈正相关关系。因此,合理的灌水和施氮能够优化根系形态及分布,提高根系活力,协调根冠干物质分配,提高产量和氮利用率。在冬小麦生产中拔节和开花期各灌水1次结合180 kg hm^(–2)施氮量有利于促进产量和氮素利用效率协同提高。

Effects of reduced nitrogen and suitable soil moisture on wheat(Triticum aestivum L.) rhizosphere soil microbiological,biochemical properties and yield in the Huanghuai Plain,China

Soil management practices affect rhizosphere microorganisms and enzyme activities, which in turn influence soil ecosystem processes. The objective of this study was to explore the effects of different nitrogen application rates on wheat(Triticum aestivum L.) rhizosphere soil microorganisms and enzyme activities, and their temporal variations in relation to soil fertility under supplemental irrigation conditions in a fluvo-aquic region. For this, we established a split-plot experiment for two consecutive years(2014–2015 and 2015–2016) in the field with three levels of soil moisture: water deficit to no irrigation(W1), medium irrigation to(70±5)% of soil relative moisture after jointing stage(W2), and adequate irrigation to(80±5)% of soil relative moisture after jointing stage(W3);and three levels of nitrogen: 0 kg ha^–1(N1), 195 kg ha^–1(N2) and 270 kg ha^–1(N3). Results showed that irrigation and nitrogen application significantly increased rhizosphere microorganisms and enzyme activities. Soil microbiological properties showed different trends in response to N level;the highest values of bacteria, protease, catalase and phosphatase appeared in N2, while the highest levels of actinobacteria, fungi and urease were observed in N3. In addition, these items performed best under medium irrigation(W2) relative to W1 and W3;particularly the maximum microorganism(bacteria, actinobacteria and fungi) amounts appeared at W2, 5.37×10^7 and 6.35×10^7 CFUs g^–1 higher than those at W3 in 2014–2015 and 2015–2016, respectively;and these changes were similar in both growing seasons. Microbe-related parameters fluctuated over time but their seasonality did not hamper the irrigation and fertilization-induced effects. Further, the highest grain yields of 13 309.2 and 12 885.7 kg ha^–1 were both obtained at W2 N2 in 2014–2015 and 2015–2016, respectively. The selected properties, soil microorganisms and enzymes, were significantly correlated with wheat yield and proved to be valuable indicators of soil quality. These results clearly demonstrated that the combined treatment(W2 N2) significantly improved soil microbiological properties, soil fertility and wheat yield on the Huanghuai Plain, China.

流畅性对审美鉴赏的影响——从加工流畅性模型到审美愉悦与兴趣模型

加工审美对象的流畅性是否对审美反应产生影响,一直存在争议。加工流畅性模型主张流畅性直接引发积极情绪,积极情绪是影响审美判断的决定性因素。而审美愉悦与兴趣模型主张加工动机决定加工水平,并导致不同的审美反应。厘清流畅性与不同审美反应间的关系,分析不同水平的加工的作用,有助于进一步完善审美加工模型。未来应关注审美需求以及不同审美对象,并结合神经美学的方法,发展和完善审美加工理论框架。