灌水和施氮对冬小麦根系特征及氮素利用的影响

Effects of water and nitrogen application on root characteristics and nitrogen utilization in winter wheat

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。

The morphological and physiological characteristics of the root system determine the ability of a plant to obtain nutrients and water.In winter wheat,to building a sensible root population structure,coordinating root-shoot growth,and improving the efficiency of N fertilizer utilization,root morphological characteristic and root activity in response to water and nitrogen(N)and their relationships with dry matter accumulation in shoots,yield,and N utilization were analyzed.A field experiment was conducted using split-plot on design two factors.Two main levels of water supply,W0(no irrigation during the whole growth period)and W1(irrigation once each at the jointing and flowering stages),and three secondary levels of N application[N0(0 kg hm^(–2)),N180(180 kg hm^(–2)),and N300(300 kg hm^(–2))]were set.Compared with W0,W1 inhibited the increase of root length density but increased the root average diameter in the 0–20 cm and 20–40 cm soil layers,increased root surface area and root dry weight density in the 0–20 cm soil layer,significantly increased root activity by 4.98%–22.7%,reduced root-shoot ratio by 1.47%–11.25%,and yield,N uptake efficiency,and partial productivity of N fertilizer increased by 15.50%,13.40%,and 14.91%,respectively.Compared with N0,N application promoted root growth,significantly increased the average root diameter,root length density,root surface area,root dry weight density,and root activity,while decreasing the root-shoot ratio.N180 was more beneficial to root growth than N300,N180 improved root morphological indicators and activity,while increasing yield,N uptake efficiency and agronomic use efficiency of N fertilizer by 2.53%,44.51%,and 39.37%,respectively.Correlation analysis revealed that root dry weight density from jointing stage to flowering stages was positively correlated with the yield and N use efficiency,while the root-shoot ratio was negatively correlated with yield and positively correlated with N use efficiency.Therefore,appropriate levels of irrigation and N application optimized root morphology and distribution,improved root activity,coordinated root and shoot dry matter distribution and improved yield and N utilization.In winter wheat production,W1N180 is beneficial to promote the synergistic improvement of yield and N use efficiency.