增密种植条件下苗期深松与氮肥侧深施对玉米根系生长与氮效率的影响

Effects of deep loosening and N side-deep fertilization during seedling stage on root growth of field-grown maize under high planting density

增加种植密度是实现玉米增产重要途径。高种植密度抑制玉米根系生长,改变根系构型,限制玉米养分吸收。如何改善根系生长,是增密增产增效的关键科学问题。以耐密玉米品种垦沃1号为材料,采用裂区试验,主区为种植密度,分别为6万株·hm^(-2)(D6)、8万株·hm^(-2)(D8);副区为氮肥施用方式:氮肥作为基肥一次性施用,记作N1T1;氮肥作为基肥+追肥分次施用,其中追肥采用“侧深松+侧深施氮肥”组合处理,利用深松施肥机同步进行,记作N2T2;以农户常规处理作为对照(CK),即氮肥一次性施用,苗期不深松。结果表明,与CK处理相比,吐丝期D8N2T1处理下单株根长、根生物量、根系表面积、比根长、节根数增幅分别达11.4%、22.0%、11.2%、13.1%、10.9%;0~60 cm土壤深度根长提高11.3%~44.6%;D8N2T1处理下,群体氮积累量增加71.1%,营养器官氮素转运效率提高51.6%,氮肥偏生产力提高102.4%,氮肥农学效率提高143.1%;D8N2T1处理下,产量达17.1 t·hm^(-2),增幅达50.6%,显著高于农户常规处理。综上,增密种植配合苗期深松与氮肥侧深施组合技术,可有效改善根系生长,促进植株氮素吸收,提高植株营养器官氮转运效率,实现增产与氮肥增效。

Increasing planting density is one of the major agronomic practices to achieve high grain yield in maize.However,high plant populations can lead to poor root growth which can limit nutrient acquisition.Therefore,constructing an efficient root system is essential for improving crop productivity and nutrient use efficiency simultaneously.In the study,a density-tolerant maize cultivar Kenwo 1 was adopted,and split plot was designed.Main plot was planting density including 60000 plants·hm^(-2)(D6)and 80000 plants·hm^(-2)(D8),respectively.In sub-plot,two chemical nitrogen fertilizer application patterns were applied.Chemical nitrogen fertilizer was 100%applied as base fertilizer,which was abbreviated as N1T1.Chemical nitrogen fertilizer was split-applied as base and sidedressing N,which was abbreviated as N2T2.Farmers'practices,in which chemical nitrogen fertilizer was 100%one-time application,was conducted as control(CK)without deep tillage during the seedling stage.By comparing with farmers'practices(CK),D8N2T1 improved root length per plant,root biomass,root surface area,specific root length,nodal root number and root growth in 0-60 cm by 11.4%,22.0%,11.2%,13.1%and 10.9%,The root length of 0-60 cm soil depth increased by 11.3%-44.6%,respectively.Meanwhile,nitrogen accumulation per population,N remo-bilization efficiency,partial nitrogen productivity(PFP),and nitrogen agronomic efficiency(AE)increased by 71.1%,51.6%,102.4%and 143.1%.Grain yield of D8N2T1 was 17.1 t·hm^(-2),which increased by 50.6%.In conclusion,increasing planting density matching with"side-and deep-"&split-N application could collectively increase grain yield through optimizing root growth,improving nitrogen accumulation and remobilization.