施氮量和密度互作对玉米产量和氮肥利用效率的影响

Interaction of nitrogen fertilizer rate and plant density on grain yield and nitrogen use efficiency of maize

【目的】施氮量、种植密度等主要栽培措施的互作效应,往往使氮肥利用效率难以估计和评价,定量分析施氮量和密度互作下玉米产量和氮肥利用效率(NUE)响应的生理过程,对玉米高产氮高效栽培具有参考价值。【方法】以郑单958为材料,在3个种植密度(4.5、7.5和10.5万株/hm2)和3个施氮量(N 0、150和300kg/hm2)条件下进行田间试验。在14叶展期(V14)、吐丝期(R1)、灌浆期(R3)和成熟期(R6)取样,采用长宽系数法测定叶面积后,将样品分为叶片、茎秆(含叶鞘、雄穗)和雌穗(R1、R3);在成熟期,将样品分为茎秆(包括叶片、茎鞘、苞叶、穗轴)和籽粒两部分,记录干质量,测定植株及籽粒全氮含量。分析了玉米碳氮积累与产量形成和氮肥吸收利用的关系。【结果】与N150相比,N300既没有提高玉米群体碳氮积累总量,也没有提高个体生产能力,氮肥利用效率较低;N150和D10.5条件下,玉米产量和氮肥利用效率最高,说明减氮增密是协同提高玉米产量和氮肥利用效率的重要途径。施氮和增密的氮素积累优势主要受V14—R3阶段干物质积累的驱动,且这种关系在花前V14前后就已经建立。V14—R3阶段干物质积累速率与氮素积累速率呈显著正相关,施氮和增密明显促进氮素积累对干物质积累的响应强度。施氮和增密下玉米以花前较低氮浓度获得较高氮积累量,也说明其花前氮积累是以花前大量茎叶干物质积累为前提,花后氮积累则主要取决于雌穗干物质积累。氮密互作对氮收获指数(NHI)无显著影响,而适宜施氮和增密显著提高HI,说明减氮增密获得较高的氮肥利用效率,而与籽粒中氮素分配多少无关,主要取决于籽粒中干物质分配的多少。【结论】施氮量和密度互作通过影响干物质积累量、产量和氮积累量影响氮肥利用效率。合理减氮增密通过促进V14—R3阶段作物生长率和花后物质生产,驱动充足的氮素积累和干物质分配,实现产量与氮肥利用效率的协同提高。

【Objectives】The interaction of N rate and plant density often makes troubles to evaluate the nitrogen use efficiency(NUE)of maize.It is of great importance to analyze the effects of interaction of N rate and plant density on physiological processes of N absorption and utilization and yield formation of maize for revealing mechanism and pathway of enhancing NUE and yield synchronously in maize.【Methods】Field were conducted using a typical commercial hybrid Zhengdan958 as tested materials in Shulinzhao and Salaqi,Inner Mongolia.The tested plant densities included 45,75 and 105 thousand plants per hectare(D4.5,D7.5 and D10.5),and N rates included 0,150 and 300 kg/hm^2(N0,N150 and N300).At the stages of 14-open-leaves(V14),silking(R1),grain filling(R3)and ripening(R6),plant samples were collected,and divided into different parts for measuring biomass,nitrogen contents.The nitrogen use efficiencies were calculated.【Results】Compared to N150,N300 neither enhanced the total carbon and nitrogen accumulation of maize,nor improved individual plant yield capacity,which induced the low nitrogen use efficiencies under the high N rate.The D10.5 combined with N150 gained the highest yield and NUE,indicated that increased plant density with reduced N rate was an important way to improve maize yield and NUE synchronously.The N accumulation advantage of applying N and increasing plant density was mainly driven by dry matter accumulation during the stage from V14 to R3.N uptake rate was positively correlated with dry matter accumulation rate at the V14-R3 stage,and applying N and increasing plant density remarkably enhanced the response intensity of N accumulation to dry matter accumulation.Under the treatments of applying N and increasing plant density,maize could acquire higher preanthesis N accumulation with lower N concentration,which indicated that pre-anthesis N accumulation primarily depended on shoot dry matter accumulation,while post-anthesis N accumulation was mainly ascribe to ear dry matter accumulation.The interaction of N rate and plant density did not affect the nitrogen harvest index(NHI),but the medium N and high plant density significantly improved HI.This indicated that enhancing NUE by reducing N rate and increasing plant density had nothing to do with nitrogen distribution to grain,but was primarily ascribe to grain dry matter accumulation.【Conclusions】The interaction of N rate and plant density influences the NUE significantly through affecting dry matter accumulation and N accumulation.Reasonable reduction of N input while increasing plant density could concurrently enhance maize grain yield and nitrogen use efficiency,which physiologically promoted crop growth rate during the bracketing silking and post-anthesis biomass accumulation,and further drove adequate pre-anthesis N accumulation and post-anthesis grain biomass distribution.