不同施氮量及基追比例对玉米冠层生理性状和产量的影响

Nitrogen rate and timing considerations on yield and physiological parameters of corn canopy

以加拿大魁北克地区推广的玉米品种Pioneer 38B84为材料,研究不同施氮量和基追比例对玉米最上一片全展开叶SPAD值、Dualex值、净光合速率（PN）、叶面积指数（LAI）、地上部生物量、冠层叶绿素密度（SPAD×LAI）、冠层光合能力（PN×LAI）以及产量的影响。试验设5个处理：N0（基0＋追0）、N20＋93（基20 kg/hm2＋追93 kg/hm2）、N45＋68（基45 kg/hm2＋追68 kg/hm2）、N113（基113 kg/hm2＋追0）和SAT225[基225（播种时施氮45 kg/hm2,播种后10 d再沟施180 kg/hm2）＋追0],完全随机区组设计,重复4次,基本苗为79000株/hm2。结果表明,追肥前,叶片SPAD值、PN、LAI、地上部生物量、SPAD×LAI及PN×LAI均随基肥氮量的增加而增加,Dualex值则降低。同等施氮量下,基肥配合追肥显著提高叶片SPAD值,而追肥对叶片Dualex值和PN无显著影响。虽然基肥配合追肥处理的LAI、地上部生物量、SPAD×LAI、PN×LAI在追肥后均显著低于氮肥一次性基施,但显著提高了玉米产量。基施氮肥20 kg/hm2与45 kg/hm2处理之间玉米产量无差异,但前者过早地表现出缺氮。总施氮量为113 kg/hm2时,其SPAD值、Dualex值、PN、LAI、地上部生物量、SPAD×LAI以及PN×LAI等指标在出苗后256~0 d与SAT225处理差异不显著,但产量却显著低于SAT225处理。本试验条件下,基肥量45 kg/hm2能较好地满足玉米前期生长,但总施氮量113 kg/hm2不能满足玉米全生育期的需求,需要进一步地评估适宜的施氮量。同等施氮量下,基肥配合追肥显著提高玉米产量;SPAD值和Dualex值均与玉米植株氮含量显著相关,SPAD和Dualex可以作为实时快速指导玉米追肥的有效工具。

One year corn field experiment was conducted at a research farm of Agriculture and Agri-Food Canada,located in L＇Acadie,Quebec,Canada.The experiment was a completely randomized block design with five N treatments and four replications.The five N treatments received N 0,20,45,113 and 225 kg/ha（N 45 kg/ha was applied at sowing,and N 180 kg/ha at 10 days after sowing）,respectively,at sowing,and N 0,93,68,0 and 0 kg/ha,respectively,at side-dressing,i.e.N0,N20＋93,N45＋68,N113,and SAT225.Corn density is 79000 plants/ha,and the cultivar is Pioneer 38B84.The results show that SPAD reading,PN,LAI,aboveground dry biomass,canopy chlorophyll density（SPAD×LAI） and canopy photosynthetic capacity（PN×LAI） are increased with basal N rates increasing before side-dressing,while Dualex reading is decreased.Compared to N113,SPAD readings in the N20＋93 and N45＋68 treatments are significantly increased.The split N applications have no significant influences on Dualex reading and PN.The LAI,aboveground dry biomass,SPAD×LAI and PN×LAI of N20＋93 and N45＋68 are significantly lower,but the grain yields are significantly higher than those of N113.There are no significant differences in corn grain yield between N20＋93 and N45＋68,however,the N deficiency is appeared earlier in N20＋93 than in N45＋68.No significant differences between N113,N20＋93 or N45＋68,on one hand,and SAT225,on the other hand,are observed in SPAD reading,Dualex reading,PN,LAI,aboveground dry biomass,SPAD×LAI and PN×LAI at 25-60 days after emergence,while corn grain yields of N113,N20＋93 and N45＋68 are significantly lower than that of SAT225.Split N application can significantly increase corn grain yield compared to only one application at sowing,and N45＋68 is better than N20＋93.Under our experimental condition,a total N application with N 113 kg/ha do not produce the same corn grain yield as SAT225.Both SPAD and Dualex readings show significant correlation with corn plant N concentration,and then can be used as an instant and non-destructive diagnostic tool for corn N status evaluation.