Effects of Planting Density on Yield Performance and Density-Tolerance Analysis for Maize Hybrids

Abstract

Plant density has been recognized as a major factor determining the grain yield.The photosynthetic performance changes as the density increases.The main objective of this research was to evaluate the response of the photosynthetic performance to planting densities in different hybrids of maize(Zea mays L.).Field experiments were conducted in Gongzhuling,Jilin province.Three corn hybrids were cultivated at 60 000 plants ha~(-1),75 000 plants ha~(-1),90 000 plants ha~(-1),and 105 000 plants ha~(-1).Treatments were arranged in a split-plot design with three replications.Plant population density was the main-plot and hybrids the subplot.The results indicated that leaf area index(LAI),leaf area duration(LAD),mean leaf area index(MLAI),and ear number m~(-2)(EN) increased and net assimilation rate(NAR),harvest index(HI),grains per ear(GN),and grain weight(GW) decreased in all hybrids as plant density intensified,as a result,the assimilate transmission rate reduced,the leaf senescence accelerated,physiological activity declined.During the growth period,the changes of LAI,LAD showed a single peak curve.The peak of LAI appeared at silking,the peak of chlorophyll content appeared at grain filling and peak of high value duration of LAD appeared from full-grown to milky maturity.The peak of NAR appeared from seeding stage to jointing and from silking to grain filling respectively.The photosynthetic characteristics were different in plant density treatments.The highest grain yield of Xianyu 335,Zhengdan 958,and Jidan 209 was obtained in the treatments of 90 000 plants ha~(-1),75 000 plants ha~(-1),and 90 000 plants ha~(-1),respectively.Kernel yield per plant decreased in all hybrids as plant density intensified.The density-tolerance of hybrids was Xianyu 335 Zhengdan 958Jidan 209.The suitable planting density range was 90 000-105 000 plants ha~(-1) for Xianyu 335,and 75 000-90 000 plants ha~(-1) for Zhengdan 958 and Jidan 209.