播期和种植密度对玉米茎秆性状及抗倒力学特性的影响

Effects of sowing date and planting density on stalk characteristics and lodging resistant mechanical properties of maize

【目的】探究不同播期和种植密度对玉米茎秆性状及抗倒力学特性的影响,为四川地区玉米高产抗倒栽培及玉米机械粒收技术的应用提供理论依据和实践指导。【方法】以‘仲玉3号’玉米为供试材料,设置6个不同的播期(3月27日、4月6日、4月16日、4月26日、5月6日、5月16日)及6.75和8.25万株/hm 22个种植密度水平。各处理玉米均在生理成熟后10 d收获,测定玉米倒伏率(根倒率、茎折率)、产量、植株农艺性状(株高、穗位高、穗位高系数)及基部第3节茎秆形态(节间长、节间粗和节间长粗比)、质量性状(节间干质量、单位长度干质量、单位体积干质量和茎秆含水率)与力学强度(穿刺强度、压碎强度、弯折强度),研究不同播期和种植密度对玉米茎秆抗倒性能的影响。【结果】播期及种植密度显著影响玉米的抗倒性能,随着播期的推迟,玉米根倒率、茎折率和倒伏率总体上先降低后增高,产量逐渐降低。随着播期的推迟,植株株高、穗位高、第3节节间长及长粗比则显著增大;节间干质量、单位长度干质量和单位体积干质量呈先降低后增高的趋势,茎秆含水率和力学强度呈先增高后下降的变化规律,以上指标均在播期4月26日或5月6日达到极值。增大种植密度使这种增高或降低效应进一步加强,玉米倒伏率显著增大。相关性分析表明,不同播期玉米生理成熟后倒伏率受降雨及刮风的影响,并与基部节间长粗比、节间干质量及力学强度显著相关,其中茎秆力学强度是引起倒伏率变化的主要原因,而节间单位长度干质量及长粗比则是影响抗倒力学的主要因素。【结论】早播及增大种植密度对玉米产量虽有一定的提升作用,但茎秆抗倒能力却较差。因此,为协调玉米高产与抗倒之间的矛盾,建议春播不宜过早,在4月中下旬播种较为适宜;夏播则不宜过晚,应尽量安排在5月上旬完成。种植密度以6.75万株/hm^(2)为宜。

【Objective】To provide theoretical and practical guidance for high yield and lodging resistance of maize cultivation in Sichuan and promote the development of mechanical grain harvesting technology of maize,this study investigated the effects of different sowing dates and densities on stalk characteristics and lodging resistant mechanical properties.【Method】The maize cultivar‘Zhongyu 3’was selected for field experiments including six sowing dates(March 27th,April 6th,April 16th,April 26th,May 6th and May 16th)and two planting densities(6.75 and 8.25×104 plants/hm 2).All samples were collected 10 days after physiological maturity of maize to measure stalk lodging rates(root lodging rate and stalk breaking rate),yield,plant agronomic traits(plant height,ear height and coefficient of ear height),basal stem morphology(internode length,internode diameter and internode length-to-diameter ratio(L/D)),quality traits(internode dry weight(DW),dry weight per unit length(DWUL),dry weight per unit volume(DWUV)and stem moisture content(MC))and mechanical strength indexes including crushing strength(CS),rind penetration strength(RPS)and bending strength(BS)of the third stem internode.【Result】Maize lodging resistance was significantly affected by sowing date and planting density.With the delay of sowing date,stalk lodging rate,root lodging rate and stalk breaking rate decreased first and then increased,while maize yield decreased gradually.The plant height,ear height,the third internode length and ratio of length-to-diameter increased significantly,while DW,DWUL and DWUV of the third internode increased after initial decreases.On the contrary,the third internode MC and mechanical strength indexes increased first and then decreased significantly.When the sowing date was delayed from April 26th to May 6th,internode morphology,quality traits,mechanical strength and stalk lodging rate reached the maximum or minimum,respectively.Increasing density further promoted the increasing or decreasing effects,which led to significant increases of stalk lodging rate.Correlation analysis showed that stalk lodging rates at different sowing dates were significantly affected by rainfall and wind after physiological maturity,and it was significantly correlated with L/D,DW,DWUL and RPS,CS and BS of the third internode.The change in stalk mechanical strength was the main reason of lodging rate variations,and the changes in DWUL and L/D were the main factors affecting mechanical properties of lodging resistance.【Conclusion】Optimizing planting density and sowing date could achieve high population yield and lodging resistance.It was suggested to sow spring maize in mid-to-late April and summer maize in early May with planting density of 6.75×10^(4) plants/hm^(2) for coordinated high yield and lodging resistance.